Tegner and Dayton 1991 Urchins, El Ninos, And Fishing Effect on Kelp

8/3/2019 Tegner and Dayton 1991 Urchins, El Ninos, And Fishing Effect on Kelp

http://slidepdf.com/reader/full/tegner-and-dayton-1991-urchins-el-ninos-and-fishing-effect-on-kelp 1/15



52 Mar. Ecol. Prog. Ser. 77:49-63, 1991

A . Average Drift By Site

30 1

18m 18m 18m 1% l 2 r

Nonh S o u l h Central Central Central

Site

B. Average Drift By Season

Table 1. Species composition of all drift collections (n = 131)

from all 5 sites from 1983 through 1986. Macrocystispyrifera is

also broken dow n by parts of the pla nt

SpeciesOO

Macrocystis pyrifera 85.37

Blades 38.88

Stipes 25.71

Fronds 12.42

Haptera 6.82

Sporophylls 1.54

Other laminarians

Pterygophora californicaPelagophyc us porra

Laminaria farlowii

Egregia rnenziesiiEisenia arborea

Agarurn firn briatumOther Phaeophyta

Desmares t ia l~yu la t a

Dictyopteris undulata

Cystoseira osmundace aPach ydictyon corn'aceurn

Dictyota flabellata

Rhodophyta

Foliose red algae

Articulated corallines

Angiosperms

Phyllospadiu spp.

Total weight 657 065 g

A. Central Forest Sites

wlnler sprlng summer fall

Se a so n

B. Outer Edge Sitesduring 1983 o 1985, ncludi ng cases of zero valu es for

both species, follocved by increases in 1986 an d 1987. lo o

These curves sugge st that recruitment was consistently 90

r

better at e dge of the forest sites than inside the bed. To 80 -

test this hypothesis, recruitment rates were ranked for 70 -

eac h of the 9 determinations at the 5 sites and analyzed60 -

w t h the Friedman 2-way ANOVA . The rankng s were l ~ m ~ ~ l t h

significant for both species (p< 0.01). posteriori tests 2 - am South

40 - - am Central(Nemenyi 1963)were conducted to determine which

30 Isites were significantly different. The mean percent 1983 1984 1985 1986

r e c ru i tmen t (lga3o fo r each site in th e Orde r ofFig 3. Macrocys t i spyn fera . Variance in the percentage of the

its ranking is given in 2 . Thus, there may drift constituted by M.pyrifera, spring 1983 through the end of

have been minor differences between the 2 species, 1986, by year. (A) Central forest sites. (B ) Outer edge sites

Fig. 2. (A) Average drift by site, all samples combined, spring E 60 -1983 through the end of 1986 (B )Average drift by season, all

2 50 -sites combined, spring 1983 through the end of 1986. Sites, 2and especially seasons, were significantly different (see text) 40 -

--f la m Central- sm Central- 2m Central

l



Mar Ecol. Prog. Ser. 77: 49-63, 1991

18m Centra l

15m Central

Description of events at 18m S- hanciscanus- purpuralus Until the fall of 1984, ther e was no indication th at18 m S was different from other forest edge sites. At

that time plants were stressed throughout the forest

12m Centra l

Fig. 10. Densities were determin ed once in 1975 on

100 X 2 m transects at the 12 and 18 m C sites running

through the same areas a s the present 25 m transects;

the habi tats are similar but not identical. ( The densities

at 12 m C were reported incorrectly in Tegner&

Dayton1981. The values should b e 0.8 and 2.1 m-2 for Strongy-

locentrotus franciscanus an d S. purpuratus, respec-

tively.) Purple urchin densities do not appear to have

change d since 1975,bu t red urchin densities have been

reduced by 1 to 2 orders of magn itude. Th e purple to

red urchin ratio has increased from 1.6 to 14.6 at 1 8 m C

and from 2.8 to 291 at 12 m C.

Fig. 5. Strongylocentrotus purpuratus and S. franciscanus.Recruitment rates during the mid 1970s (Tegner & Dayton

1981) compare d with 1983 to 1987 as computed on a n annu albasis for 3 sites in the central forest. Data were computed from

m2 samples of urchin aggr egation s

through 1987 at 4 of the 5 st udy sites (Fig. 7; ANOVA, p

> 0.05). The densit ies of both species increased a t 18 mS (p < 0.001 in each case) . At this site, an examination

of the density changes line by line illustrates that some

of th e increase can be att ributed to migration from an

A. 18m Central

B. 12m Central

Z Density < 35 mm- enslly > l00mm

urchin-dom inated area south of line D, which increased Fig. 6 .Strongylocentrotus franciscanus. Densities of young-of-

faster than line C, etc. (Fia.8). However, increases in the-year and large adult red urchins from the mid 1970s\ d ,

recruitment also preceded increases in density , espe- (Tegner& ~ a ~ t o n 1 9 8 1 )nd 1983 to 1987 at 18m C nd 12 m

C sites computed from the mZ amples of urchin aggregations.cially for Strongylocentrotus franciscanus (Fig. 9). The decline in adult density between the mid 1910s and theDensities from the mid 1980s are compared with 1980s was signif icant at both site s and juvenile recruitment

values obtained in 1975 (Tegner & Dayton 1981) in was significantly lower at 12 m C in the 1980s (see text)



Tegner & Dayton: Sea urchins, El Ninos, and kelp forests 63

Sokal, R. R., Rohlf, F. J. (1969). Biometry. W. H. Freeman and

Co., San Francisco

Tegner, M . J. (1980). Multispecies conside rations of r esource

managem ent in Southern California kelp beds. Can. Tech.

Rep. Fish. Aquat. Sci. 945: 125-143

Tegner, M. J. (1989). The feasibility of en hanc ing red se a

urchin (S trongylocentrotus francis canus) stocks in Califor-

nia; a n analysis of the options. Mar. Fish. Rev. 51(2): 1-22

Tegner, M. J. , Dayton, P. K. (1977). Sea urchin recruitment

patter ns and implications of commercial fishing. Science

196: 324-326

Tegner, M. J. , Dayton, P. K. (1981). Population str ucture ,

recru itment , and mortality of two sea urchins (Str ongy-

locentrotus franciscanus and S. purpurat us) in a kelp

forest. Mar. Ecol. Prog. Ser . 5: 255-268

This article was presented by N. Holland, La Jolla, California,

USA

Tegner, M. J., Dayton, P. K. (1987). El NiAo effects on South-

ern California kelp forest communities. Adv. ecol. Res. 17:

243-279

Tegner, M. J., Levin. L. A. (1983). Spiny lobsters and s ea

urchins: analysis of a predator- prey interac tion. J. exp.

mar Biol. Ecol. 73: 125-150

Tutschulte, T C. , Connell, J. H . (1988). Feeding behavior and

algal food of thr ee specie s of aba lones ( Hahoti s) in South-

ern Calif ornia. Mar Ecol. Prog. Ser . 49: 57-64

Vadas. R. L. (1977). Preferential feeding: an optimization

strategy in sea urchins. Ecol. Monogr. 47: 337-371

Wilson, K. C., Haaker, P. L., Hanan, D. A. (1977). Kelp restora-

tion in Southern California. In: Krauss, R. (ed.) The marine

plant biomass of the Pacific Northwest coast. Ore gon State

University Press, Corvallis, p. 183-202

Manuscript first received: Nove mber 6, 1989

Revised version accepted: A ugust 21, 1991

Tegner and Dayton 1991 Urchins, El Ninos, And Fishing Effect on Kelp

Documents

Transcript of Tegner and Dayton 1991 Urchins, El Ninos, And Fishing Effect on Kelp