60(3), 1998 15

Introduction

Marine recreational bottom fishingfrom commercial passenger fishing ves-sels (CPFV’s), known as partyboats andcharter boats, has been popular in theMonterey Bay area of central Califor-

Declining Rockfish Lengths in the Monterey Bay, California,Recreational Fishery, 1959–94

JANET E. MASON

The author is with the Pacific Fisheries Environ-mental Laboratory, National Marine FisheriesService, NOAA, 1352 Lighthouse Ave., PacificGrove, CA 93950.

ABSTRACT—California’s Monterey Bayarea is an important center of recreationalfishing for rockfish of various Sebastes spe-cies. The species composition of commer-cial passenger fishing vessel catches from1959 to 1994 varied with changes in fish-ing location and depth. The shift from shal-low nearshore locations to deeper offshorelocations in the late 1970’s and 1980’schanged the emphasis from the blue rock-fish, S. mystinus, of shallow waters to thedeeper, commercially fished chilipepper, S.goodei, and bocaccio, S. paucispinis. Themean size of rockfish in the catch increasedas the latter species were targeted at greaterdepths but then declined as stocks of olderfish disappeared by the mid 1980’s. During1960–94 the mean size of all ten leadingspecies in the recreational catch declined.The declines ranged from 1% for canaryrockfish, S. pinniger, to 27% for chilipepper.The sizes of the deeper living species de-clined more than those of shallower species.The low frequency of strong recruitmentevents and increase in fishing mortality andnatural mortality appear to have contrib-uted to the declining mean size. The scar-city of older fish, observed as a drop in meansize to below the size of maturity for 50%of females, leads to concern for future re-cruitment of the larger species, especiallybocaccio, chilipepper, yellowtail rockfish, S.flavidus, and canary rockfish.

nia since the late 1920’s (Clark andCroker, 1933). Passengers pay a fee tobe taken to one or more offshore fish-ing sites, where they fish while the boatdrifts over bottoms from 9 to 274 mdeep (Sullivan, 1995). The skipper lo-cates concentrations of fish on the bot-tom or in midwater, and anglers catchan average of 11–12 fish per day(Karpov et al., 1995). For the purposeof this paper, the Monterey Bay area,approximately 100 km south of SanFrancisco, includes all sites normallyfished by CPFV’s from the ports ofSanta Cruz, Moss Landing, and Mon-terey (Fig. 1) and extends from AñoNuevo, about 35 km north of SantaCruz, to Point Sur, about 35 km southof Monterey. This area received 24% ofCPFV effort and produced 43% ofCPFV landings in northern Californiafrom 1981 to 1986 (Karpov et al., 1995).Most of the fish caught (85%) are ofthe genus Sebastes, commonly calledrockfish (Miller and Geibel, 1973;Karpov et al., 1995).

Rockfish have dominated the catchfrom CPFV’s in the Monterey Bay areafrom the 1950’s to the present (Millerand Geibel, 1973; Karpov et al., 1995;Reilly et al.1; Wilson-Vandenberg etal.2). At least 29 species of rockfish ap-pear in the CPFV catch (Miller and

Geibel, 1973), but the fishery heavilytargets the few aggregating speciesfound in limited areas. Over 72% of thecatch in 1960–86 (Mason, 1995) and76% in 1987–91(Reilly et al.1) camefrom six aggregating species: bocaccio,S. paucispinis; chilipepper, S. goodei;blue rockfish, S. mystinus; yellowtailrockfish, S. flavidus; widow rockfish, S.entomelas; and olive rockfish, S.serranoides. Over the years the propor-tions of these species in the catch havechanged from predominantly blue rock-fish in the 1950’s, to both blue and yel-lowtail rockfish in the 1960’s (Millerand Geibel, 1973), to more chilipepperand bocaccio in the 1980’s (Mason,1995), and back to more blue rockfishin the 1990’s (Wilson-Vandenberg etal.2,3; Wilson et al.4).

The continuous harvest of rockfish bythe CPFV fishery has raised questionsabout the sustainability and health ofthis fishery. Some anglers and boat op-erators believe that rockfish are smaller

1 Reilly, P. N., D. Wilson-Vandenberg, D. L.Watters, J. E. Hardwick, and D. Short. 1993. Onboard sampling of the rockfish and lingcod com-mercial passenger fishing vessel industry innorthern and central California, May 1987 toDecember 1991. Calif. Dep. Fish Game, Mar.Res. Div. Admin. Rep. 93-4, 242 p.

2 Wilson-Vandenberg, D., P. N. Reilly, and L.Halko. 1995. Onboard sampling of the rockfishand lingcod commercial passenger fishing ves-sel industry in northern and central California,January through December 1993. Calif. Dep. FishGame, Mar. Res. Div. Admin. Rep. 95-2, 122 p.3 Wilson-Vandenberg, D., P. N. Reilly, and C. E.Wilson. 1996. Onboard sampling of the rockfishand lingcod commercial passenger fishing ves-sel industry in northern and central California,January through December 1994. Calif. Dep. FishGame, Mar. Res. Div. Admin. Rep. 96-6, 96 p.4 Wilson, C. E., L. A. Halko, D. Wilson-Vandenberg, and P. N. Reilly. 1996. Onboardsampling of the rockfish and lingcod commer-cial passenger fishing vessel industry in north-ern and central California, 1992. Calif. Dep. FishGame, Mar. Res. Div. Admin. Rep. 96-2, 103 p.

16 Marine Fisheries Review

and less available than in the past, es-pecially close to port. Reilly and co-workers1 studied the species composi-tion, mean length, and catch per anglerhour in the fishery from 1987 to 1991.They found variation in the mean lengthof individual species and recommendeda longer study to determine trends. Inthis paper, I combined 8 years of theirstudies with earlier data to provide alonger historical perspective on meanlengths of the ten dominant rockfishspecies over a 34-year period. Thesechanges will be reviewed in light of therelative abundance of the species in thecatch and the effect of new recruitmenton mean length in the catch.

The relative importance of particu-lar rockfish species has changed withtheir availability over the years and withthe CPFV fleet’s response. Blue rock-fish dominated the catch in the firstCPFV survey by the California Depart-ment of Fish and Game (CDFG) in1959–60 (Miller and Gotshall, 1965).Miller and Gotshall expressed concernabout the declining availability of bluerockfish which dropped that year from54% to 18% of the local Santa Cruzcatch. Blue rockfish aggregate in shal-low water <70 m deep (Miller andGeibel, 1973). Like most rockfish spe-cies, they do not migrate and are there-fore easily depleted in local areas.

Miller and Geibel (1973) found that95% of blue rockfish recaptured fromtagging releases inside kelp beds werefound at the release site over a 3-yearperiod, and that 85% of recaptured adultblue rockfish from tagging outside kelpbeds moved <1.6 km. Length distribu-tions of the catch from fishing areas 15km apart remained distinct over severalyears, confirming the isolation of localpopulations and the lack of replenish-ment by adults from other areas despitedifferences in fish density (Miller andGeibel, 1973).

As catches of blue rockfish declinednear Santa Cruz in the 1960’s, CPFVskippers maintained high catch ratesthrough two strategies: fishing fartherfrom port for blue rockfish or shiftingto deeper water to target other speciessuch as yellowtail rockfish (Miller andGeibel, 1973). Boats from Santa Cruzlocated concentrations of blue rockfishat Año Nuevo, 15 km from port, but af-ter a few years even these distant stocksdeclined in mean length and in avail-ability. In the area nearer port, yellow-tail rockfish became the leading speciesin the catch, taken in midwater overbanks from 66 to 100 m deep (Millerand Gotshall, 1965).

A second shift to fishing in evendeeper water occurred by 1977 aschilipepper rockfish, caught near thebottom at depths averaging 116–135 m(Sullivan, 1995), became the dominantspecies (Mason, 1995). Bocaccio,greenspotted rockfish, S. chlorostictus,and greenstriped rockfish, S. elongatus,were also caught at these depths. Thesefour species are used in this report asindicators of deepwater fishing (depthsof 75 m or deeper). Bocaccio occur inshallow water as juveniles and in deepwater as adults, and are consideredmixed-depth species in some studies(Karpov et al., 1995). In the MontereyBay area they are generally taken byCPFV’s at 75 m and deeper (Thomasand Bence 1992; Sullivan, 1995; Reillyet al.1), and thus are deepwater speciesfor this fishery.

The Monterey Bay area had the high-est proportion of deepwater species inthe total recreational catch of any areain northern and central California dur-ing 1981–86 (Karpov et al., 1995). The

proximity of deepwater fishing sitesalong the Monterey Canyon and CarmelCanyon makes these species more avail-able to CPFV’s from Monterey Bay thanfrom other ports. The percentage ofCPFV trips to deepwater areas inMonterey Bay recorded by CDFG in-creased from 56% in 1987 to a maxi-mum of 72% in 1990–91(Reilly et al.1,Wilson-Vandenberg et al.2,3; Wilson etal.4). Deepwater trips dropped to 28%by 1994 as effort shifted back to bluerockfish in shallow water after 1992(Wilson-Vandenberg et al.2,3).

The sport and commercial fisheriestargeted different species until the1970’s, but as CPFV’s moved intodeeper water, that distinction disap-peared. Chilipepper and bocaccio havedominated commercial rockfish land-ings in Monterey Bay for more than 100years. Bocaccio and chilipepper to-gether accounted for 70% of the land-ings from set lines in 1937–38; yellow-tail rockfish, vermilion rockfish, S.miniatus, and canary rockfish, S.pinniger, totaled another 21% (Phillips,1939). Bocaccio and chilipepper re-mained dominant despite changes incommercial fishing gear from set linesin the 1930’s, to balloon trawls in the1950’s, to gillnets in the late 1980’s(Heimann, 1963; Pearson and Ralston,1990). From 1980 to 1994 chilipepperand bocaccio have dropped from 80%to 54% of the rockfish catch. The rela-tive importance has shifted from mostlybocaccio before 1984 to mostly chili-pepper after 1990. The commercialhook-and-line fishery has increased inboth landings and proportion of thecommercial catch since 1990 (Pearsonand Almany, 1995). A nearshore hook-and-line fishery for live fish has devel-oped throughout the state since 1989(California Department of Fish andGame, 1998). As the CPFV fleet movedinto deep water and the commercialfleet into shallow water, fisheries inter-actions increased.

Changes in the relative abundance ofparticular species of rockfish can beinferred from their proportion in theCPFV catch, but relative importancemay be affected by trends in abundanceof other target species, as well aschanges in fishing locations. Another

Figure 1.—Extent of the MontereyBay CPFV fishing area on the centralcoast of California.

60(3), 1998 17

indicator of the condition of the fisherymay be the size of fish caught. The an-nual mean length of the total CPFVrockfish catch reflects the average sizeof all species combined, and a drop inthis mean may indicate either an in-creased proportion of smaller species inthe catch or a decreased size of thedominant species. It is necessary to lookat both the size of individual species andtheir changing proportions in the catchto evaluate changes in overall size.

A decline in the mean length of afished species is often considered anindicator of increased fishing mortality.A large proportion of the biomass forunexploited rockfish populations con-sists of older, larger, slower growing fish(Leaman and Beamish, 1984). In-creased fishing pressure removes theseolder fish more rapidly than they arereplaced, so if recruitment and growthare stable, higher fishing mortality willreduce the mean length. In rockfishpopulations, however, recruitment var-ies from year to year, and the size dis-tribution of young fish varies with thepresence or absence of successful yearclasses. A strong year class can domi-nate the catch as it recruits to the fish-ery, first reducing and then increasingthe mean length as the year class grows.If another strong year class recruits to thefishery, the mean length may drop again.

I examined the CPFV fisheries fromMonterey Bay for: 1) changes in fish-ing effort and success, 2) changes inrelative importance of species from dif-ferent depths, 3) changes in the size ofthe ten leading species, 4) the meanlength caught relative to size at matu-rity, 5) the effects of new recruitmenton the mean length of these species, and6) similar trends in the mean length ofspecies from CPFV and commerciallandings.

Methods

Total catch of rockfish was takenfrom annual summaries of the logbookssubmitted by CPFV skippers to the Cali-fornia Department of Fish and Game.Individual rockfish species are not re-corded in the logbooks, so I estimatedthe annual catch by species by multi-plying the total rockfish caught by theannual proportion of each species de-

rived from the sampling programs. Thetotal number of anglers is also recordedin the CPFV logbooks, and since alltrips out of the Monterey Bay area areday trips, the number of anglers repre-sents angler days. The years covered bythe various sampling programs are dis-played in Figure 2.

Catch per angler day (CPAD) wascalculated in two ways. Simple CPADwas calculated from the total catch di-vided by the total anglers. This includedall types of CPFV fishing in theMonterey Bay area. CPAD from rock-fish trips was what remained after theeffort and catch from trips targetingPacific salmon, Oncorhynchus spp.,were removed from the total trips. Formost of the time series, the effect ofsalmon trips on CPAD is negligible, butCPFV logbooks indicate more salmonhave been caught since 1986. Boatstrolling for salmon catch very few rock-fish. From 1987 to 1994 CDFG exam-ined the logbook records for each fish-ing trip and removed salmon trips(CPFV trips that caught salmon andaveraged less than 4 fish per angler)from the calculation of rockfishing ef-fort (Reilly et al.1; Wilson-Vandenberget al.2,3; Wilson et al.4). Data were notavailable to make this correction forprevious years.

The CDFG also compared the num-ber of anglers and fish reported in log-books for observed trips with the actualnumbers observed by CDFG samplersto determine the unreported catch and

effort for 1987–94. Adjusted total rock-fish and rockfish effort were calculatedfrom these rates. The CDFG also cat-egorized the trips by fishing depth dur-ing this period (Reilly et al.1; Wilson-Vandenberg et al.2,3; Wilson et al.4).

Data on species composition andlength frequency were gathered fromseveral sampling programs spanning a34-year period in the Monterey Bay area(Fig. 2). The earliest data are from theCentral California Marine Sport FishSurvey (Miller and Gotshall, 1965;Miller and Geibel, 1973). Species com-position and lengths of blue rockfishwere recorded each year from 1959 to1972 except for 1965. Lengths of allrockfish species were sampled fromCPFV’s only in 1960, 1961, and 1966.The California Cooperative RockfishSurvey collected species compositionand length information from CPFV’s for1977–86 for Santa Cruz and Montereyand for 1979–81 for Moss Landing (allMoss Landing CPFV’s had moved toMonterey by 1982). The creel censusportion of the Marine Recreational Fish-ery Statistics Survey collected data onspecies composition and length for1979–86 for Santa Cruz County andMonterey County ports and overlapswith the previous survey (Holliday,1984). These data augment reducedsampling by the California CooperativeRockfish Survey during these years.Data sources through 1986 and numbersof fish sampled are further described byMason (1995). The Central California

Figure 2.—Sources of data. Logbook data provide total CPFV catch and effort;salmon removed indicates years salmon effort was subtracted from the logbooktotal to calculate catch and effort for just rockfish trips. Surveys measuring speciescomposition and length frequency in various years include: CCMSFS — CentralCalifornia Marine Sport Fishing Survey, years when only blue rockfish were mea-sured; CCMSFS all spp., years when all species were measured; CCRS — Califor-nia Cooperative Rockfish Survey; and MRFSS — Marine Recreational Finfish Sta-tistical Survey.

18 Marine Fisheries Review

Marine Sport Fish Project again col-lected samples from 1987 to 1994, andtheir sampling techniques are describedby Reilly et al.1 In 1990, samples weretaken only from January to June, and in1991 from August to December so these2 partial years were combined to re-move the seasonal differences in spe-cies composition.

All sampling programs measured to-tal length of rockfish in millimeters.Frequency distributions were calculatedin 0.5 cm length intervals (e.g. 10.0 to10.4 cm) and grouped to 2 cm for dis-play and labeled by lower limit of in-terval. Mean lengths for species werecalculated from the total lengths foryears with at least 20 measured fish ofa species. The 10 leading species wereused for analysis of mean length be-cause they had nearly complete series.Boundaries for the 10th and 90th per-centiles were calculated from 0.5 cmlength-frequency categories and used toindicate the size range. Mean lengthswere compared to the sizes at which50% of the females and 50% of themales reach sexual maturity, as de-scribed by Wyllie Echeverria (1987) fornorthern California rockfish.

Length frequencies were expandedby catch by multiplying the total catchof rockfish reported in the CPFV log-books times that species’ proportion inthe sampled catch times the proportionin each 2 cm size class. Length frequen-cies for four species with at least 50 fishper year were used to produce thelength-frequency time series.

Only the California CooperativeRockfish Survey (1977–86) identifiedthe sex of rockfish when collectinglengths from the CPFV’s. These lengthswere used to examine sexual dimor-phism in length frequency for each sexfor each of the ten leading species.

Estimated weights of rockfish landedby CPFV’s were derived from the esti-mated annual catch by species to com-pare CPFV and commercial landings. Icalculated weights from the length fre-quencies by using length-weight param-eters calculated from studies in south-ern California (Love et al., 1990), ex-cept for blue rockfish which Miller andGeibel (1973) studied in the MontereyBay area. I divided the estimated CPFV

species landings by the sum of CPFVlandings and expanded commerciallandings from the California port sam-pling program data (Pearson andRalston, 1990; Pearson and Almany,1995) to get the percent caught byCPFV’s. Logbooks may underestimatethe CPFV catch by the proportion offishing trips that are not reported, sopercentages are adjusted to include un-reported catch. I also calculated meanlengths of species by commercial geartype from this sampling program forprincipal species occurring in both theCPFV and commercial fisheries. Totalcommercial rockfish landings were ob-tained from the series of annual com-mercial landings published by the Cali-fornia Department of Fish and Game(1980–95).

Results

Many aspects of the CPFV fisheryhave changed during the 35 years cov-ered by this report. There have been in-creases and decreases in effort and intotal catch, as well as changes in thespecies caught and the depths fished.Declines in the proportion of certainspecies in the catch may reflect reducedavailability of these species or increasedavailability of alternate species. Thecatch of smaller fish indicates a scar-city of large fish of particular speciesavailable to this fishery. All of thesechanges must be examined in relationto each other to evaluate the conditionof the fishery.

Catch and Effort

Total catch by CPFV’s increasedthreefold from 1964 to 1982 (Fig. 3a).Rockfish ranged from 81% to 95% ofthe catch and averaged 91% from 1959to 1994. The rise in catch closely re-flects the increased fishing effortthrough 1982 (Fig. 3b). Effort droppedsharply from 1983 to 1985 and catchdropped in 1984–85. As effort droppedin 1983, CPAD peaked (Fig. 3c) butdecreased the next year as catch alsodropped. Total effort climbed to a sec-ond peak in 1988, but total catch didnot increase proportionately (Fig. 3a),probably because more effort was di-rected toward Pacific salmon whichbecame more available after 1985.

When salmon become available,many boats troll for them instead ofbottom fishing for rockfish. Salmonavailability increased in the local area,and their catch rose from 2,500 (1.0%of CPFV catch) in 1985 to about 10,000salmon (2.8% of CPFV catch) in 1986(shown at 10 times actual catch in Fig.3a). From 1987 to 1994, salmon fish-ing accounted for an average of 26% ofthe CPFV effort and a maximum of 34%in the combined 1990–91 seasons.

Catch per angler day differs for tripsbottom fishing for rockfish and tripstrolling for salmon. Marine anglers inCalifornia may keep 20 fish per day, 15may be one or more species of rock-fish, but only two may be salmon. Theaverage catch of rockfish has variedfrom 8 to 13 fish per angler day (Fig.3c). Catch per angler day for salmontrips averaged less than 4 fish per an-gler day. What appears to be a declin-ing trend in catch per angler day after1982 (Mason, 1995) was calculatedfrom total fish divided by total anglers.When salmon fishing trips are removedafter 1986, CPAD for rockfish tripsstays at 10–12 fish per day. Salmon ef-fort was negligible in earlier years, ex-cept for 1959–62, 1964, 1967, and 1986when salmon totaled 1% or more of theCPFV catch. The low rockfish CPADin 1985 reflects both a slight increasein salmon effort and low availability ofrockfish.

Total catch and effort for the Mon-terey Bay area may have declined lessthan the logbooks indicate. Althoughskippers are required to report the num-ber of trips along with the number ofpassengers and the number of fishcaught, not all trips are actually re-ported. Skippers reported 73% of boththe actual number of anglers and the fishcaught on trips observed by CDFG inthe area from 1987 to 1991 (Table 76in Reilly et al.1) and only 58% of thenumber of anglers and 56% of the catchfor 1992–94. The percentage of tripsreported dropped from a peak of 87%in 1988 to a low of 48% in 1994. Thecatch reported has also dropped forthose years (from 73% to 84%: Wilson-Vandenberg et al.2,3; Wilson et al.4).Adjusted total catch and rockfish effortare indicated only after 1986 (Fig. 3, a

60(3), 1998 19

Figure 3a.—Catch from Monterey Bay area CPFV’s: TOTAL FISH =Total fish re-ported; 10 X SALMON = salmon plotted at 10 times reported numbers; ROCK-FISH = total rockfish reported; ADJ. TOTAL RF = total rockfish adjusted upwardsfor percentage not reported in logbooks. 3b.—CPFV effort in Monterey Bay area:TOTAL ANGLERS = total anglers reported; ANGLERS RF TRIPS = anglers fromtrips targeting rockfish (not salmon trips); ADJ. RF ANGLERS = anglers fromrockfish trips adjusted upwards for percentage not reported in logbooks. 3c.—CPFVcatch per angler day: CPAD = all fish from all trips; CPAD RF TRIPS = all fishfrom trips targeting rockfish; RFPAD = rockfish per angler day, all trips; RFPADRF TRIPS = rockfish per angler day from trips targeting rockfish.

and b), since we do not have compli-ance data for earlier years. Thus thedecline in total catch and effort in 1993–94 may be slightly exaggerated by un-der reporting.

Species Composition

Catch composition has changed overtime with changes in the depth and habi-tat fished. Blue rockfish was the lead-ing species taken in the late 1950’s.From 1959 through 1972 blue rockfishand yellowtail rockfish dominated, av-eraging 35% and 21% of the catch, re-spectively (Fig. 4). Olive rockfish aver-aged 6% of the catch and other shal-low-water species together averagedonly 3% through 1972. Since 1977, fourspecies caught in deeper water (below75 m) have become very important tothe fishery averaging 32% of the catchin 1977–94 as compared to 7% in 1959–72. Most important in this group ischilipepper, which increased from 2%of the catch in 1959–72, to 15% in1977–85, and 21% in 1986–94. Thethree other members of the deepwatergroup (bocaccio, greenspotted rockfish,and greenstriped rockfish) also in-creased in relative importance after1977, although from 1991 to 1994 theydeclined sharply from 38% to 17% ofthe catch. Species compositions for1990–91 are averaged from two incom-plete sampling years (see Methods).

The relative importance of the differ-ent species groups varied more after theexpansion into deeper water in 1977than in earlier years. The fleet did notshift completely away from shallowwater, but moved among different fish-ing areas at different depths, thus tar-geting a greater variety of species. Themost blue rockfish were landed byCPFV’s (estimated at 290,000) in 1981after the fishery diversified into deepwater. High fishing effort and goodavailability of species from all depthranges contributed to the record totallandings in 1981–82 (Fig. 3a). The catchincluded chilipepper, bocaccio, andwidow rockfish from deep water, yel-lowtail rockfish from intermediatedepths, and blue rockfish from shallowwater. After 1978, total catch peakedonly in years when blue rockfish wereavailable, such as in 1988 and 1993. The

proportion of the catch comprising thefour deepwater species has steadily de-clined since 1986 (Fig. 4) despite in-creased deepwater trips in 1989–92(Table 1). The proportion of trips todeep water did not decline appreciablyuntil 1993–94. The ten leading rockfishspecies are listed by order of abundancein the annual landings for the entire timeperiod in Table 2.

Sexual Dimorphism

Sexual dimorphism in total bodylength was present in some but not allspecies of rockfish sampled from 1977to 1984 (Fig. 5). Sexual dimorphismwas pronounced in blue rockfish: only7% of the males were larger than themean length of females. Only 4% ofchilipepper males were 40 cm or larger

20 Marine Fisheries Review

Figure 4.—Cumulative percentage of CPFV-caught rockfish by dominant singlespecies (blue rockfish and yellowtail rockfish) and species groups based on depth.Blank areas are years without sampling of rockfish species.

Table 2.—Rating and percentage contribution of the ten most abundant species in the CPFV catch from 1959–94.

Rank Common name Scientific name Percent contributed

1. Blue rockfish S. mystinus 27

2. Yellowtail rockfish S. flavidus 16

3. Chilipepper S. goodei 11

4. Bocaccio S. paucispinis 7

5. Widow rockfish S. entomelas 5

6. Olive rockfish S. serranoides 5

7. Rosy rockfish S. rosaceus 3

8. Greenspotted rockfish S. chlorostictus 3

9. Canary rockfish S. pinniger 3

10. Greenstriped rockfish S. elongatus 2

Total contribution of top ten species 82

Table 1.—Percentage of CPFV trips to two depthranges. Trips classified as mixed depth could not beseparated into just one depth range.

Trips (%)

Shallow Deep MixedYear (<80 m) (>80 m) depths

1987 17 56 27

1988 22 56 21

1989 19 63 17

1990–91 19 72 9

1992 20 64 16

1993 7 40 53

1994 31 33 36

compared to 52% of females. Only 8%of male olive rockfish were larger thanthe mean length of females. Only 4%of male greenstriped rockfish werelarger than the mean length of females.In all four of these species, the femalesattained a larger maximum length anda larger mean length than the males.

Some species (bocaccio, widow rock-fish, and yellowtail rockfish: Pearsonand Ralston, 1990) that are sexually di-morphic at larger sizes were less clearlydimorphic in the sizes taken by theCPFV fishery. The mean length of fe-males was only slightly larger than thatof males, but in each of these speciesfemales predominated in the largest sizeclasses. Yellowtail rockfish males ap-peared to have a narrower size distribu-tion than females, but since somesampled fish, especially immature ones,were not categorized by sex, the appar-ent lack of smaller males may resultfrom a difficulty in identifying immaturemales. Canary rockfish and rosy rockfishdid not display sexual dimorphism in thelengths taken from CPFV’s, althoughBoehlert and Kappenmann (1980) foundthat canary rockfish females caught byresearch trawls had a larger mean length,and Pearson and Ralston (1990) foundthat canary rockfish females were moreabundant than males in the larger sizerange from commercial trawls (>56 cm,a size not occurring in the CPFV samples).The mean length of greenspotted rock-fish males was slightly larger than themean length of females, and this is theonly species in which males averagedlarger than females. Greenspotted rock-fish and rosy rockfish are not dimorphicin length, according to Lenarz and WyllieEcheverria (1991).

Lengths

The mean lengths of the ten mostabundant rockfish species caught onCPFV’s in Monterey Bay between 1960and 1994 are presented in Fig. 6. Thespread between the 10th and 90th per-centiles of lengths represents the sizerange of 80% of the catch. Plots oflength frequencies (Fig. 7) displaychanges in lengths for four species.

The time series of blue rockfishlengths is the most complete becauseonly blue rockfish were sampled

throughout the 1960’s (Fig. 6). Thesharp drops in mean length and the 10thpercentile of length in 1962, 1964, and1968 reflect small fish recruiting to thefishery. Increasing mean length from1970 to 1972 can be attributed to thegrowth of the new recruits observed in1968 (Fig. 7). Mean length was great-est during the period of highest catches(1977–84). Length frequencies indicatea mode of larger fish at about 34 cm aswell as a mode of smaller fish at 26–28cm visible in 1981; this bimodalitycould be produced by two or more rela-

60(3), 1998 21

Figure 5.—Sexual dimorphism in length distributions of ten leading rockfish species caught by CPFV’s in Monterey Bay in1977–86 (California Cooperative Rockfish Survey data); each 2 cm group is shown as a fraction of total males or total females(n = number sampled per sex).

tively strong year classes separated byless strong year classes, but also reflectsthe pronounced sexual dimorphism ofthis species. Mean length dropped in1984 as larger fish became less abun-dant in the catch; after that only 42% ofthe catch was larger than the size (29cm) at which half of blue rockfish fe-males mature (Wyllie Echeverria,1987). In 1977–84, 79% of the fishsampled were female. It is not knownif the smaller mean length after that re-

flects more males in the catch or smallerfemales, but few fish have reached thelarge sizes present in 1977–83.

Yellowtail rockfish were largest in1977, 1983, and 1991 (Fig. 6). New re-cruitment to the fishery appeared as adrop in the length of the 10th percen-tile in 1978, 1984, and 1987. Growthof these recruits can be tracked in themean length and in the length frequen-cies of the catch for the next four years(Fig. 7). Since 1985, large fish have

been scarce and only 32% of the yel-lowtail rockfish have been above thelength (36 cm) at which half of the fe-males reach maturity, compared to 54%from 1977–84. The drop in 1994 to thelowest size for both the mean length andlength of the 10th percentile may indi-cate new recruitment to the fishery, es-pecially since yellowtail rockfish con-tributed a significant proportion (15%)of the CPFV catch in that year, but alsoreflects the smaller size of fish caught in

22 Marine Fisheries Review

shallow water. Half of the yellowtail rock-fish were caught in shallow water in 1994as compared to 10% in earlier years(Reilly et al.1; Wilson-Vandenberg et al.3).

Chilipepper had the most dramaticand sustained decline in mean length ofthe catch, 14 cm from 1960 to 1994(Fig. 6). The increasing mean lengthduring 1980–82 resembled growth of

Figure 6.—Changes in length over time for ten leading species of rockfish: meanlength, heavy line; 10th percentile, dashes; 90th percentile, light line. Breaks inlines indicate missing or insufficient data. Data are discontinuous for all speciesexcept blue rockfish in 1962–65 and 1967–76. Size at maturity for 50% of speciesis indicated by horizontal lines: female = heavy line; male (if different from fe-male) = light line.

5Rogers, J. B., and J. R. Bence. 1992. Review ofthe fishery and auxiliary data for chilipepperrockfish in the Conception/Monterey/EurekaINPFC areas: a qualitative assessment of the sta-tus of the stock in 1992. In Appendices to thestatus of Pacific groundfish fishery through 1992and recommended acceptable biological catchesfor 1993: Stock assessment and fishery evalua-tion. Pac. Fish. Manage. Counc., Portland, Oreg.18 p.

recruits but was faster than the growthrates of either males or females de-scribed by Wilkins (1980) or Rogers andBence.5 This increase in mean lengthmay indicate several older year classesexploited by an expanding fishery ratherthan growth of a single year class. Thedrops in the 10th percentile of length in1986 and in mean length and 90th per-

centile in 1987 indicate a surge of newrecruits, which can easily be seen in thelength frequencies (Fig. 7). Catches ofchilipepper soared in 1987 with a strongsingle mode of fish that remained domi-nant for the next 2 years. The growthrate in this period is consistent withgrowth rates for females described byWilkins (1980) and Rogers and Bence.5

By 1989, the peak broadened as malegrowth slowed, but by 1990 this mode’scontribution had greatly declined andcatches of chilipepper decreased. After1984 there was a noticeable lack oflarger fish; only 48% were 34 cm orlarger (the size of maturity for half ofthe females) when compared to 74%during 1977–84. The proportion of fe-males in the catch after 1986 is notknown, but during 1977–86, 71% of theidentified fish were female. Since 1992,the mean length has been below thelength at maturity (34 cm) for 50% offemales (Fig. 6). Although this dropmay be caused by recruitment, the num-ber of chilipepper in the catch has con-tinued to decline, indicating that recruit-ment was only moderate.

Bocaccio had the largest mean lengthand 90th percentile of the ten leadingspecies and also the greatest fluctuationin mean length in the catch. The meanlength of bocaccio dropped dramati-cally from its largest mean in 1983 toits smallest just 2 years later. This dropin mean length and in the 10th percen-tile in 1985 reflected new recruitmentto the fishery, and these new recruitsdominated the bocaccio catch for thenext 4 years (Fig. 7). Noticeable recruit-ment to the fishery also occurred in1979, 1981, and 1990. Fish larger thanthe size of maturity of 50% of females(48 cm) have constituted 41% of thebocaccio catch since 1984, but beforethat they contributed 65%. Mean lengthhas been below the size of maturity of50% of females but above the length at

60(3), 1998 23

Figure 7.—Estimated annual CPFV catch for four leading species of rockfish by 2cm length-frequency categories, 1959 at top to 1994 at bottom. The vertical scale attop displays the number of fish indicated by the height within each curve.

maturity of 50% of males in all but 2years since 1987 (Fig. 6).

The longest mean lengths for widowrockfish were recorded in 1960–61 and1982 (Fig. 6). In 1982 an increasedcatch of large widow rockfish raised thelength of the 90th percentile and con-tributed more to the increase in meanlength than did the growth of smallerfish. Fewer than 20 widow rockfishwere measured per year in 1978–79, sothese years (when widow rockfish con-stituted less than 1% of the catch) arenot included in the graph. The drop inthe mean length and in the 10th percen-tile in 1987, followed by increasingmean length through 1992, indicate apulse of recruitment to the fishery.Widow rockfish reached their highestpercentage in the catch in 1988, as thesenew recruits were targeted. The return tosmaller fish in 1993–94 may indicate newrecruitment. More than half of the widowrockfish caught by CPFV’s are juveniles;the mean length has been at or below thelength at maturity for 50% of females (37cm) and males (36 cm) since 1983.

The mean length of olive rockfishremained constant at about 40 cm from1977 to 1984, but then it declined (Fig.6). New recruitment to the fishery wasapparent in 1988, followed by an in-crease in mean length to 1992. The dropin the 10th percentile of length in 1993–94 reflects recruitment of small fish.The percentage of olive rockfish in thecatch is generally less than 5%, but itjumped to 18% in 1980 and to 9% in1983. These increases in catch did notcoincide with pulses of new recruitmentas they did for bocaccio and chilipepper.The mean length has remained above thelength of maturity (35 cm) for 50% offemales throughout the period examined.

Rosy rockfish had the smallest meanlength of the ten most abundant species(Fig. 6). Mean length of rosy rockfishvaried little, but it dropped 1 cm from1982 to 1983 and then gradually de-clined to 1994. The 10th percentile oflength also declined by 2 cm and mayhave been affected by the discard ofsmall fish. Rosy rockfish are not tar-geted by the fishery but are a smallerspecies caught incidentally to other spe-cies. Small fish are sometimes thrownback as “too small” even though expan-

sion of their air bladder from rapid de-compression causes them to float anddie. The percentage of rosy rockfishretained (not discarded) in 1987–91does not have an obvious trend but hasvaried between 84% and 93% in theMonterey Bay area (Reilly et al.1; Wil-son-Vandenberg et al.2,3; Wilson et al.4).Earlier discard rates might have beenhigher. Almost all of the rosy rockfishsampled were above the length at ma-turity (20 cm) for 50% of the femalesthroughout the time series.

Greenspotted rockfish mean lengthwas larger in 1977–83 than in 1960, andit declined after 1987 to its lowest sizein 1994. There are no apparent periodsof recruitment and growth. The 10th

percentile of length has declined despitethe high retention rate of this species(97–99% in 1987–94). In all years, themean length was above the length at ma-turity (28 cm) for 50% of the females.

Canary rockfish mean length variedover the study period and was largestin 1981–82. Periods of recruitment tothe fishery in 1977 and 1984 are indi-cated by sharp 1-year declines followedby sustained increases in the 10th per-centile and mean length. The most re-cent drop in mean length has been con-tinuous since 1990. Canary rockfishmean length has been below the lengthat maturity of 50% of females through-out the study, and since 1983, 90% ofthe canary rockfish caught in the CPFV

24 Marine Fisheries Review

fishery have been juveniles, below thelength at maturity of 50% of females(44 cm) and 50% of males (40 cm).

The mean length of greenstripedrockfish fluctuated only slightly overthe study period. The species is caughtincidentally to targeted deepwater spe-cies such as chilipepper and bocaccio,and the mean length was the secondsmallest of the ten most abundant spe-cies in the catch. The mean length hasdeclined steadily from 1989 to 1994.Despite their relatively small size, mostof the greenstriped rockfish were re-tained: 96% in 1987–91(Reilly et al.1)and 93% in 1994 (Wilson-Vandenberget al.3). Over 90% of them were largerthan the length at maturity for 50% offemales and males (both 23 cm).

There has been a net decline in themean length of all ten dominant speciesbetween 1960 and 1994 (Table 3). Thedecline occurred after 1977 for all but

two of the species. Eight of the ten spe-cies dropped at least 4% in mean lengthduring this period. Chilipepper, bocac-cio, widow rockfish, and yellowtailrockfish declined the most, droppingmore than 10% in mean length from1960 to 1994.

Mean Lengths FromCommercial Fisheries

The declining mean length trends ofchilipepper and bocaccio from theCPFV fishery were also present in thecatch from the commercial trawl andgillnet fisheries (Fig. 8). The new re-cruitment evident in the CPFV fisheryin 1985–87 can also be identified by adrop in mean length in the trawl and thegillnet fisheries. Gillnet mesh size se-lects larger fish which explains thelarger mean length caught by this fish-ery and the delay in recruitment untilfish reach gear-selected size. The de-

cline in mean length of chilipepperrockfish was more gradual in the trawlfishery, where escapement related tomesh size or processor preference maylimit the minimum size, than in theCPFV or gillnet fisheries.

The mean lengths of widow and yel-lowtail rockfish from CPFV’s were no-ticeably smaller than the means fromtrawls and gillnets and may reflect es-capement of smaller fish and the onto-genetic movement of older fish todeeper water (Love et al., 1990). Yel-lowtail rockfish are not targeted bytrawlers in Monterey Bay and contrib-ute only 5%, on average, of the com-mercial rockfish catch, so data are lesscomplete. Mean lengths for commer-cially caught widow and yellowtail rock-fish declined over time, coming closer tothe mean lengths from CPFV’s.

Grouped Species LengthsGrouping rockfish species together in

different ways can reveal the largertrends in the fishery. The mean lengthof all rockfish caught on CPFV’s was 3cm (8%) larger in 1977 than in 1960–61, but varied before dropping sharplyin 1994 to 10% below the 1960–61mean (Fig. 9).

Comparing the relative contributionof larger and smaller species to the fish-ery reveals periods in which shiftingproportions of these two groups affectedmean length. Two size categories ofspecies were created based on averagemean length from 1960–94. As ex-pected, the five species with averagemean lengths of 35 cm or larger (bocac-cio, chilipepper, canary rockfish, oliverockfish, and yellowtail rockfish) in-

Table 3.—Percentage of change in total length for topten rockfish species from CPFV’s over two time peri-ods. Negative numbers indicate declining size.

Percent change

Species 1960–77 1960–94

Blue rockfish 3.01 –6.84

Yellowtail rockfish 4.12 –12.07

Chilipepper –11.65 –27.31

Bocaccio 0.95 –12.28

Widow rockfish –12.40 –11.35

Olive rockfish 0.25 –8.91

Rosy rockfish 4.82 –1.93

Greenspotted rockfish 1.79 –4.12

Canary rockfish 1.11 –1.35

Greenstriped rockfish 1.04 –4.28

Figure 8.—Mean lengths of four rockfish species from two commercial fishinggears compared to means from CPFV. Heavy line represents mean from bottomtrawls; circles represent mean from gillnets; diamonds represent means from CPFV’s.Horizontal lines are as described in Figure 6.

60(3), 1998 25

creased in the catch from 41% in 1959–72 to 48% in 1977–85, when meanlength of total rockfish was high. Aslarge species continued to increase inimportance (to 53% of the catch in the1985–94 period), however, the meanlength of total rockfish dropped. Theproportion of large species remainedhigh until the proportion of blue rock-fish increased (in 1993–94), at whichpoint the mean length dropped evenmore. The mean length decreased from1983 to 1992 despite an increased pro-portion of large species.

Grouping the species together byfishing depths reveals the influence ofdeepwater species on the overall meanlength (Fig. 9). In 1960, when blue rock-fish and yellowtail rockfish contributedabout 60% of the catch, the mean lengthfell between the means of these twospecies. As the catch shifted to deep-water species by 1977, the mean lengthincreased. Four key species (bocaccio,chilipepper, greenstriped rockfish, andgreenspotted rockfish) caught in deeperwater increased from 7% to 32% of thecatch between 1972 and 1977. Themean length of the deepwater group wasover 40 cm (11 cm larger than the meanlength of blue rockfish in 1977).

The mean length for all combinedrockfish was bounded by the means of

the deepwater group and blue rockfishfrom 1977 to 1987 (Fig. 9). Deepwaterspecies decreased in mean length from1977 to 1980, as young bocaccio andchilipepper recruited to the fishery, butthen increased in length to a maximumin 1982–83. Bocaccio contributed sig-nificantly from 1981 to 1983 and theirlarger size during this period is reflectedin the longest mean length for total rock-fish. Blue rockfish were also at theirlargest size from 1977 to 1983 and con-tributed to higher total means. The meanlengths of all the important groups de-creased in 1984–85 with a scarcity oflarge fish, and remained low through1987. Despite the increased proportionof deepwater species (columns in Fig.9), the overall mean length was reducedin this period by the smaller size of thedominant species.

Both yellowtail rockfish and thedeepwater species group increased insize in 1989–91 with the growth ofyoung fish, and their high proportion inthe catch kept the mean length of allcombined rockfish close to that of thedeepwater group. The length of thedeepwater species group declined after1991 with the reduced proportion ofbocaccio and declining size of chilipepper,greenspotted rockfish, and greenstripedrockfish; yellowtail rockfish size also de-

clined. The difference in size between thedeepwater group and blue rockfish shrankfrom 10 cm in 1991 to only 5 cm by 1994.The mean length for all combined rock-fish reached its lowest recorded level in1994 as smaller blue rockfish contributedmore to the catch. The smaller size of thedeepwater species has noticeably affectedthe overall mean length.

Discussion

Reduction of the mean length of fishcaught by a fishery is often used as anindicator of increased mortality rate. Inthe Monterey Bay area CPFV fishery,the mean length of rockfish has de-clined; however, the interpretation ofthis trend is complicated by the changesin species composition of the fishery.The decline in size results from a de-cline in the mean length of the domi-nant species as well as from shifts inthe relative contribution of various spe-cies to the catch. Several factors whichvary over time contribute to the declin-ing overall size of rockfish caught byCPFV’s: 1) changes in target species,2) removal of larger fish by bothCPFV’s and commercial fisheries, 3)environmental effects on mortality andrecruitment, and 4) declining proportionof spawning adults.

The change in target species fromshallow-water species to deepwater spe-cies in 1977–78 increased the meanlength of combined rockfish in thecatch. Large chilipepper and bocacciowere available in these deeper areasthrough 1983, but a shift back to shal-low-water fishing for blue rockfish in1979–84 moderated the mean length(Fig. 9). The return to deepwater fish-ing in 1985–89 did not increase theoverall mean length, because the sizeof fish in the deepwater group haddropped. Although the mean length ofthe group of deepwater species waslarger than that of the shallow-waterspecies (blue rockfish), the periods af-ter 1977 with higher proportions ofdeepwater species did not correspondwith the largest mean lengths for totalrockfish. Changes in target species ex-plain only the 1977–81 changes in totalmean length.

Variability in the size of dominantspecies affected the overall mean length

Figure 9.—Proportion of the four deep-water rockfish species (bocaccio, chilipepper,greenspotted rockfish, and greenstriped rockfish) in the total CPFV catch indicatedby columns, scale on left. Mean length indicated by scale on right: dashes = groupof four deep-water rockfish species, circles = yellowtail rockfish, dotted line =bluerockfish, and line with diamonds = total rockfish.

26 Marine Fisheries Review

more than species composition after1981. One component of that meanlength is the proportion of large fish inthe catch. The mean length of severalimportant species (bocaccio, chili-pepper, blue rockfish, widow rockfish,and yellowtail rockfish) reached a maxi-mum in 1982–83 from both growth ofyoung fish and accumulation of largerfish from abundant year classes pro-duced in the mid-1970’s or earlier(Beamish, 1993; Rogers and Bence5;Ralston et al.6). For example, largechilipeppers (40–50 cm) composed halfof the chilipepper catch in 1977–78.Chilipeppers of this size, estimated at7–15 years old by von Bertalanffy age-at-length equations (Rogers and Bence5),were produced before 1971, when bothrecreational and commercial fishingwas less intense. In the first few yearsthat CPFV’s fished in deep water, manylocations had accumulations of largefish. Fishing pressure, as indicated bylandings of rockfish, peaked in 1982 inthe Monterey Bay area for both CPFV(Fig. 3a) and commercial fisheries. Asfishing pressure increased, large fishwere caught and removed more rapidlythan they were replaced, and smallerfish dominated the catch. CPFV’s couldno longer find locations with unexploitedpopulations of large fish. The proportionof large fish in the catch dropped from1983 to 1985 as indicated by the re-duced size of the 90th percentile ofbocaccio, chilipepper, yellowtail rock-fish, canary rockfish, and widow rock-fish. Declining mean lengths for bocac-cio and chilipepper in the trawl andgillnet fisheries indicated fewer largefish in commercial fisheries as well(Fig. 8).

Although both CPFV’s and commer-cial fisheries remove large rockfish,their relative impact differs among spe-cies. Bocaccio are heavily exploited by

commercial fisheries; their annual takefor 1982–94 has been estimated at 20–30% of the biomass, and by 1994 theestimated biomass had dropped to about17% of its 1980 level (Ralston et al.6).Bocaccio has experienced the most dra-matic decline in biomass of the com-mercial rockfish species in the Mon-terey Bay area, but sustained fishingpressure has also resulted in decreasedmean lengths of commercially caughtchilipepper and widow rockfish (Fig. 8)and reduced the availability of large fishto CPFV’s.

The larger deepwater species (bocac-cio and chilipepper) are harvestedmostly by the commercial fisheries.Average estimated percent landed byCPFV’s of the combined CPFV andcommercial landings for 1980–94 aredisplayed in Table 4. CPFV’s took nomore than 18% of chilipepper and 27%of bocaccio in any year. CPFV’s alsotook less widow rockfish than weretaken by commercial fisheries.

Shallower species such as blue rock-fish have been taken primarily by therecreational fishery. CPFV’s also tooka high percentage of mid-depth yellow-tail rockfish and canary rockfish; thesespecies are commonly caught by com-mercial trawlers at ports farther north,but yellowtail rockfish averaged only5% and canary rockfish only 0.5% ofthe commercial rockfish catch in theMonterey Bay area from 1980 to 1994.Thus, CPFV landings have a large lo-cal impact on blue, yellowtail, and ca-nary rockfish, but commercial fisherieshave a greater effect on bocaccio,chilipepper, and widow rockfish.

Increased natural mortality as well asincreased fishing mortality during the

northern El Niño of 1982–83 may havereduced the proportion of large rockfish.Yellowtail rockfish and widow rockfishgrew more slowly, and yellowtail rock-fish, chilipepper, and blue rockfishweighed less relative to their lengthduring strong El Niño events (Lenarzet al., 1995; VenTresca et al., 1995).These species appear to be stressedwhen changes in ocean circulation re-duced the nutrient levels and availablefood. Zooplankton volumes were re-duced in 1982–83 (McGowan, 1985),and primary productivity and euphausidabundance were below normal duringthe 1992 El Niño (Lenarz et al., 1995).The pattern of strong upwelling alter-nating with periods of onshore advec-tion, important to the production ofmacrozooplankton prey for blue rock-fish (Hobson and Chess, 1988), was dis-rupted during the 1982–83 El Niño(Norton et al., 1985). These factors in-dicate reduced prey for rockfish, whichincreased feeding stress, decreased theirfitness, and may have increased mor-tality. The lack of food may have alsomade rockfish of all sizes more vulner-able to CPFV hook and line fishing;overall catch per unit of effort was high-est in 1982–83.

In addition to increased natural mor-tality of adults, El Niño environmentalconditions also reduced first-year re-cruitment of most rockfish species(Lenarz et al., 1995). Wide variationsin abundance of young-of-the-year re-cruits have been observed over 10 yearsfrom both midwater juvenile trawls andfrom in situ counts of settled juveniles(Ralston and Howard, 1995). Years suchas 1983 with high sea surface tempera-tures produce particularly poor yearclasses for most rockfish species stud-ied. Recruitment for many of these spe-cies improved after the El Niño; aver-age oceanic conditions returned produc-ing a surge of young-of-the-year in 1984and 1985. These year classes first ap-peared in the fishery as drops in the 10thpercentile and mean length. Bocaccio,the fastest growing species, was the firstto appear in the fishery with a few smallfish in 1985 and more in 1986. Chili-pepper appeared in 1986–87, and yel-lowtail rockfish in 1987–88. The growthof these new recruits was the dominant

Table 4.—Estimated percentage of weight taken byCPFV’s from combined commercial and CPFV landings1980–94. Values adjusted for under-reporting of catchin CPFV logbooks.

Weighttaken

Common name Scientific name (%)

Blue rockfish S. mystinus 83

Yellowtail rockfish S. flavidus 40

Chilipepper S. goodei 9

Bocaccio S. paucispinis 9

Widow rockfish S. entomelas 11

Greenspotted rockfish S. chlorostictus 65

Canary rockfish S. pinniger 63

6 Ralston, S., J. N. Ianelli, R. A. Miller, D. E.Pearson, D. Thomas, and M. E. Wilkins. 1996.Status of bocaccio in the Conception /Monterey/Eureka INPFC areas in 1996 and recommenda-tions for management in 1997. In J. Glock andS. K. Krause (Editors), Appendix Volume 1: Sta-tus of Pacific groundfish fishery through 1996and recommended acceptable biological catchesfor 1997: Stock assessment and fishery evalua-tion, p. B1–B48. Pac. Fish. Manage. Counc.,Portland, Oreg.

60(3), 1998 27

cause of increasing mean lengths until1991.

Variable success of year classes is asignificant characteristic of rockfishpopulations (Leaman and Beamish,1984). Several dominant rockfish spe-cies in the CPFV catch, especiallychilipepper, bocaccio, yellowtail rock-fish, and widow rockfish, recruitedstrongly to the fishery in 1977–80 fromyear classes produced in the mid-1970’s, and in 1985–87 from 1984–85year classes. The fishery appears to havedepended on these strong recruitmentevents for most of the catch after 1984(Fig. 7). Strong recruitment pulses arenot apparent in the less heavily targetedrockfish species such as olive, green-striped, greenspotted, and rosy rockfish,because they have a reserve of olderyear classes to buffer the effect of newrecruitment. Without the reserve of olderfish, the targeted species are highly vul-nerable to recruitment variability.

Recruitment success may vary withenvironmental conditions between de-cades as well as between years. Oceansurface temperature off Californiachanged from below average to aboveaverage around 1976 (Smith, 1995).This change produced more than a de-cade of warm conditions that may havelimited recruitment of colder-water spe-cies to central California, similar to thereduced recruitment of blue rockfishand olive rockfish at the edge of theirrange in southern California during1978–81 (Stephens et al., 1984). So in-stead of a few years between success-ful recruitment, some species may haveexperienced longer periods with littlerecruitment (Hollowed and Wooster,1995). The accumulated larger bocac-cio, chilipepper, yellowtail rockfish, andblue rockfish in 1977–83 may have beenthe product of several years of success-ful recruitment during the colder yearsbefore 1976. Relatively large yearclasses appear to be less frequent after1985.

Rockfish are generally long lived,with over half of the species reachingmaximum ages of 60 years or more(Love et al., 1990). They take an aver-age of 5 years to reach sexual maturity(Wyllie Echeverria, 1987). The prolongedreproductive phase for unexploited popu-

lations (from about age 5 to 60) servesas a buffer against periods of recruit-ment failure due to environmental varia-tions (Leaman and Beamish, 1984). Inthe CPFV fishery, half of the catch ofthe large rockfish species (bocaccio,chilipepper, yellowtail rockfish, andwidow rockfish) and 90% of canaryrockfish are now taken before sexualmaturity. Only smaller species such asrosy and greenstriped rockfish usuallyreach sexual maturity before they arecaught. Fishing down the reservoir ofolder, sexually mature fish removes thebuffer and increases the risk of pro-longed recruitment failure.

A similar decline in the availabilityof large rockfish was noted by Love etal. (1998) in the Southern CaliforniaCPFV catch. They noted a dramaticdecline in the catch from 3.0 to 0.4 rock-fish per hour for 21 target species from1980 to 1996, and they noted a shiftfrom predominantly larger species tosmaller species. The catch rate declinedfor most large species including bocac-cio and chilipepper, and the mean sizedeclined for several large species in-cluding chilipepper, vermilion rockfish,copper rockfish, and greenspotted rock-fish. They noted a lack of adult fish inthe catch of several species. Thesechanges in Southern California indicatethe declining size and availability ofrockfish in California is widespread andnot localized to the Monterey Bay area.

Fishery managers should be con-cerned for the health and sustainabilityof species with mean length at or be-low that of maturity. Bocaccio, chili-pepper, yellowtail rockfish, and canaryrockfish all fall into this category in theMonterey Bay area. If significant newrecruitment is the cause of the recentdeclines in mean size, it should be trace-able in the length frequency modes offish from 1994 onward. If there is nostrong mode of young fish, we mustassume that recruitment is not keepingup with removals by the combined rec-reational and commercial fisheries.

Summary

The mean length of rockfish caughtin the late 1970’s increased as CPFV’smoved into deeper water. The meanlength was generally larger for deep-

water species than for shallow-waterspecies, and large individuals werecaught from 1977 through 1983. Asurge of new recruitment after the 1982–83 El Niño produced a sharp drop inmean length of several important spe-cies and a decline in combined rockfishmean length. Mean lengths did not re-cover to the high levels of 1982–83 de-spite the growth of these recruits andthe continued emphasis on deepwaterspecies through 1991.

Fish were harvested by both theCPFV and commercial fisheries atsmaller sizes after 1982, and meanlength and total landings have droppedin both fisheries. CPFV’s shifted backtoward shallow water as the differencein size between the deepwater and shal-low-water species decreased in 1992–94. The mean length of bocaccio,chilipepper, and yellowtail, canary, andblue rockfish caught on CPFV’s hasdropped below the size at which 50%of the females mature.

Since 1984, the period betweenhighly successful recruitment eventsseems to have been longer for the domi-nant species in the catch, and recruitshave been harvested by CPFV’s andcommercial fisheries (depending onspecies) at smaller sizes than in the past,within a few years of entering the fish-ery. Since new recruits often appear inthe CPFV catch at least 1 year ahead ofthe commercial catch, the CPFV fish-ery could serve as an indicator of therelative strength of new recruitment.

Acknowledgments

This study would not have been pos-sible without the conscientious work ofmany CDFG sportfish samplers and bi-ologists over the years, especiallyDaniel Miller and Daniel Gotshall. Ithank Linda Garrett for assembling andediting the data for this report. I thankRichard Parrish, Jerry Norton, MarkHelvey, Debra Wilson-Vandenberg, andJulie Olfe for their helpful commentson the manuscript, and Tone Nichols forher graphics expertise.

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