Rssumé or RESEARCH woax nous

RESUMé OF RESEARCH WORK DONE

INTRODUCTION

one of the most important objectives of research in

capture fisheries is to understand the state of exploitedstocks and to suggest possible options for rational exploi­tation, to ensure continued and sustained production of fish.To fulfill this, it is essential to understand the taxonomicidentity of each species contributing to the fishery, itsdistribution in space and time, the various aspects of biologyof the species that influence the fishery and enable makingestimates of vital statistics and finally to estimate theparameters of growth, mortality and selection which are usefulin stock assessment studies.

Organised research on marine fishery resources of Indiawas started during late forties. During that period, the fis­hing used to be predominantly by artisanal craft and gear inthe nearshore waters and the exploitation of each species wasat a much-less—than-optimum level. During that period, theresearch efforts were mainly directed at describing thefisheries and in a few cases towards making preliminary stu­dies on bionomics. The situation underwent tremendous changewhen mechanised fishing was introduced in sixties and thenpopularised. These and the location of lucrative fishing grou­nds in the inshore waters together with the development of anexport trade of fish and fishery products, paved the way forexcellent growth of the fishing industry. and, consequentlythe total mrine fish landings increased from around half-a­million tonnes in fifties to around 2.3 million tonnes innineties. This development process not only brought to light

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several resources which were not exploited or, exploitedonly marginally prior *0 introduction of mechanised fishing,but also their vulnerability to increased fishing pressure,necessitating scientific management of the resources througha reliable information base particularly on fishing effort,catch, seasonal variations in availability and abundance inrelation to changes in environment and on the biologicalcharacteristics of the exploited species.

There was considerable difficulty in identifying the spe­cies accurately, because, in a large number of families ofmarine fishes, several closely-resembling species existed.Besides, many species came to light after the publication ofthe "Fishes of India" by Day (1878). More recently, the deli­mitation of known species and introduction of nomenclaturalchanges have caused confusion and lead to use of incorrect

scientific names or application of one name 'to more than onespecies. These have emphasised an urgent need for directedresearch in taxonomy of several exploited marine fish families.

In the case of many species, there was practically noinformation on aspects of biology such as food and feedinghabits, spawning and fecundity, growth and migration whichwere essential prerequisites for understanding spawning habitsand seasons, deleniating spawning grounds, estimating recrui­tment, understanding fluctuations in availability and abundancestudying dynamics of the populations. As the fishery was stillin a developing stage untill about a decade-and-a-half back,the effect of exploitation was not felt in respect of manystocks. Consequently, due consideration was not given to

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the estimation of population parameters and to stock assess­ments. The need for developing expertise in this major areaof research also, was therefore, not considered. It was onlyafter the catches of major exploited stocks started declining,that the imperative need to reorient the efforts towardsstock assessment and management was realised. Accordingly,through the steps taken by the CMFRI and the training pro­grammes arranged and organised by the Food and AgriculturalOrganisation of the U.N. and the Danish International Develop­ment Agency jointly for the benefit of the fisheries Scientistsin the tropical countries, that research work in fish stockassessment began receiving its due attention in India.

The author had the opportunity to carry out researchesin taxonomy, biology and population dynamics of major exploi­ted fish stocks such as threadfin breams, silverbellies, cros­kers, scad and others. The results of the studies;most ofwhich happenned to be the first ones from the seas aroundIndia, contributed significantly to the enhancement of know­ledge on the above aspects of the concerned fish species.

EAiRfI_T:__-l; E s'17AX°N91fiYt

1. on some interesting and new records of marine fishes fromI ndia 0

This work reestablished the status of the two species

of the family Drepanidae: grepane pungtgtg (Linnaeus, 1758)and Q. longimana (Bloch and Schneider, 1801). Several authorstreated them as synonymous, inspite of their distinctnessestablished by Lele (1924). Utilising the material collectedfrom Palk Bay and Gulf of Mannar and examining them for both

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morphological and anatomical characters, it was shown thatthe two species were indeed distinct and valid. A key toidentify these two species was also given.

For the first time, the presence of barbels in 3-4 rowsbelow the chin in smaller individuals of Q. punctata andQ. longimana was reported. It was also reported that thesebarbels disappear in larger fishes over 270mm in total length.

This paper also reported two species of fish, gggtholglig§D£g?¥Qp§§ (Bleeker, 1351) and Platycephalus igaganthug (Cuvier1829) for the first time from Indian seas, along with detaileddescriptions. §t§§hOjn}i§ integrnpta (Bleeker) of the familyLabridae was known from western and eastern parts of IndianOcean; the single specimen collected from the Gulf of Mannerwas the first report from the central Indian Ocean in generaland from the Indian coastal waters in particular. Platycephalusisacanthus (Cuvier) (Family Platycephalidae) was known onlyfrom western Pacific and eastern Indian Ocean. The report fromthe Gulf of Manner and Pa1k.Bay was the first from India andCentral Indian Ocean.

2. On the fishes of the family Platycephalidae of the seasaround India.

A taxonomic revision of the family Platycephalidae wasmade. This was the first comprehensive taxonomic work on the

family from India after Day (1878). Studying the fresh materialcollected from along the Indian coast, the collections availa­ble in the Zoological Survey of India, Calcutta and consultingthe data on certain type specimens, a taxonomic revision ofthe family was attempted. In view of the confusion in assi­gning the species to their respective genera, some earlier

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authors (eg. de Beaufort and Briggs, 1962) preferred to includeall the species under the single genus Blatycephalgs. Thisissue was examined in this work and the thirteen specieswere included under six genera tentatively. Detailed descri­

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ptions were given for the first time utilising the charactersof ridges and spines on the head and keys for the identifica­tion of genera and species were given.

Of the thirteen species dealt with (against the sevenspecies dealt with by Day, 1878), yahiyus erratus (Cuvier,s

1829) which was first described from Sri Lanka, was not report­ed from any where else in the world though a mention of itsname, that too erroneously, was made from a few localities.The description in this paper, on the basis of material fromLakshadweep sea, was the first from the region, in additionto the first adequate description of the species after itsoriginal description in 1829.

glatycephalus carbunculus (Cuvier, 1829) was first descri­bed on the basis of a few specimens from off Bombay and sub­sequently there was no description of this species from anywhere else in the country. The material collected from theeast coast of India, in the study, was the first report onits extended distribution from the east coast of India.

3. Nemipterus luteug (Schneider, 1801) (Nemipteridae,Pisces)the valid name for a threadfin bream from the Indo-Pacificregion.

After a critical review of the literature, studyingthe data of type specimens of relevant nominal species andexamining specimens collected from Kakinada, along the east

coast of India, it was shown that yemipterus luteug (Schneider,

1801) was the valid name for the species which was referredearlier as N. striatus (Valenciennes 1830) N. filamentosus-- ’ ’ an ‘ ."f;.1'::*"-"-~—‘*t:'_:r~ , " - .;(valenciennes, 1830), §. negatophorus (Bleeker, 1853 a) andQ, gecronemus (Gunther, 1859). A detailed description of thespecies was given for the first time from India.

4. §emipterus mesgprion (Bleeker, 1853) (Nemipteridae,Pisces)a new record from the seas around India,

On the basis of collections made at Kakinada along the

east coast of India, Nemipterus gesgprion (Bleeker, 1853 b)was first reported from the seas around India and adequatedescription was given. For the purpose of accurate identifi­cation of the species, the data of the holotype of the speciesin the Leiden Museum was consulted and the original and sub­sequent descriptions by Bleeker (1853 b, 1873, 1877) werealso studied and details presented in the paper.

To distinguish this species £rom.§. Japgnicus (Bloch),particularly in preserved condition, because colour is" themost important character in threadfin breams, a comparison of

§, mesopgion and Q, igppnicus was made and the differencesexplained to enable accurate identification of the two species.

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PART II BIOLOGY AND POPULATION DYNAMICS‘P —,__,‘_—'_:1._ ‘, 1%T':TQT__T H — ,_,' .__ '_.l-Q _:I_ ' _ “_;"“ '_' "'7' |_f‘ ‘ "‘ ‘

A. THREADFIN BREAMS

The threadfin breams (N§@iptgrg§ BPP) which are exploitedby trawlers are one of the major demersal finfish resources ofIndia. In 1993, an estimated 86752 tonnes of threadfin breamswere landed (Anon., 1994) which formed about 8.0% of total

demersal fish landings and 4.0% of total marine fish landingsof India, These fishes are known to be more abundant in rela­

tively deeper waters of 100-200 m (Silas, 1969; Silas gt 31,,1976; Zupanovic and Mohiuddeen, 1973; Philip and Joseph, 1988:

John, 1989: Sudarsan gt §l., 1990; Sivaprakasam_g§_gl., 1991)and are known to move into relatively shallower inshore waters

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during certain periods (Banse, 1959: Nair and Jayaprakash, 1986)particularly along the west coast. Among the maritime states,Kerala accounted for maximum catch which formed about 52% of

total threadfin bream catch, followed by Maharashtra (l€%),Tamil Nadu (11%), Karnataka (9%). Gujarat (8%) and others.A total of six species contribute to the fishery of whichflemipterus Jappniggg and §,‘Qg§gp£i2§ are most abundant,constituting the bulk of threadfin bream landings. The othertolu luteuspecies: Q. , Q. delagoae,_§. s and §. metgpiasoccur in the catches occasionally in small quantities.

5. Observations on some aspects of biology of threadfin breamqgmipterus mesgpriog (Bleeker) from Kakinada.

After reporting the occurrence of ggmiptgrgs mesopriogin the Indian seas and publishing, a detailed description ofthe species from Kakinada (Murty, 1981), investigations on thebiology of this species were carried out from Kakinada duringJanuary 1976-March 1980. This was the first original research

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work on the biology of §. gesopriog from the Indian Oceanregion: the lone earlier report was from east Malaysia

(Weber and Jothy, 1977» on the basis of survey data obtainedduring March 29-May 1, 1972. The 1ength~weight relationshipwas calculated as Log w= -4.650901 + 2.877071 Log L. Examin­

ing 29S females of the length range 83-177 mm, the length atfirst maturity (50% maturity) was determined as 100 mm. Bystudying the ova diameter frequency distribution in mature and

ripe ovaries, it was shown that §. mesopriog was a fractionalspawner releasing the ova in two batches during the protractedspawning season. On the basis of occurrence of females in diff­erent stages of maturation during different months and taking

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into consideration only the fishes of and above length at firstmaturity, the spawning period was determined as Decemberehprilwith peak during January in the sea off Kakinada.

Using the length data of 2386 specimens of the lengthrange 32-215 mm and following the modal progression method,

the growth of Q. mesoprion was studied: the parameters of von

Bertalanffy growth equation were estimated as as LaC= 219 mm,

K= 0.83248 per year and t°= —0.256198 year. The life-span inthe fishery was estimated as three years.

6. Observations on the fisheries of threadfin breams (Nemipt—eridae) and on the biology of Nemipterpsyjaponicgs (Bloch)in the trawling grounds off Kakinada.

Using the data collected by the author during 1976-'79from the landings of small commercial trawlers operating offKakinada, the fishery of threadfin breams and biology of

yemdpterus japgnicus were studied. This was the first study inIndia on the basis of data collected from commercial vessels,

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the earlier studies in the country being based on data ofexploratory vessels operating off Andhra—0rissa coasts(Krishnamoorthi, 1973), off Cochin (Vinci and Nair, 1975;Vinci, 1983) and off Mangalore (Kuthalingam, 1971).

During the study period, four species of threadfin breams

contributed to the fishery. Qgmipterus japgnicus was the mostdominant species supporting the fishery, followed by Q. ggsoprion,Q. and _1§I_. . It was shown that November-May was thetolu luteusperiod of abundance of_nemipterids in the trawling grounds offKakinada.

The reproductive biology of Q. japgnicus was studied.The testes were small even in mature fishes and it was notpossible to quantify them into different maturation stages.The ovaries were, however, classified into six stages of mat­uration on the basis of external appearance ( size in relationto body cavity, colour, nature of intraovarian ova as seen bynaked eye) and structure and size of intraovarian ova undermicroscope. Fully spent fish were never encountered. Thelength at first (50% maturity) maturity was estimated as 125 mm

in females. Like Q. meggpriog (Murty, 1982), §, japgnicus wasalso shown to be a fractional spawner, spawning in two spawn­ing acts during the spawning period. The nature of ova diameterfrequency distribution in mature and ripe ovaries and thenon-occurrence of spent or spent rematuring females (over 1000females examined during 1976-'79 period) were shown to be

suggestive that the females once reaching ripe stage would notrevert to "stage II" (rematuring adults or spent recoveringadults) as was generally believed to be the case in Indian

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marine fishes and in most temperate water fishes which were

known to spawn during shorter periods, once a year. By cons­idering females above length at first maturity and on the basisof frequency of occurrence of mature and ripe females indifferent months, the spawning was shown to extend from.Augustto.April with peaks during December and February. This conclu­sion was supported by the occurrence of smaller fishes in the35-85 mm length range over extended periods.

For the first time in Indian marine fishes, an attempt toestimate total annual fecundity of a fractional spawner wasmade in the case of §. japgpicug from off Kakineda. The totalannual fecundity in fishes of 134-199 m total length range wasestimated as ranging from about 23000 to 139200. The relation­ship between total length and fecundity was estimated asF= -116.56711 + 1.11909 L: (r=0.83) and between weight andfecundity as F= -0.75615 + 1.11380 wx (re 0.92).

The sex ratio showed predominance of males; the largestlength of males was observed to be 285 mm and that of femalesto be 215 mm. The possibility of faster growth rate of malesas suggested by Krishnamoorthi (1976) and Eggleston (1973)was recognised in this study also (see Qasim, 1966 also).

Using the length data of over 6600 specimens of thelength range 35-285 mm collected during 1977-'79 and follow~ing the monthly progression of modes in the length frequencydistribution, the growth rete was estimated. The von Bertallanffy

parameters of growth were estimated as La? 314 mm, K= 0.75 peryear and to= -0.17 year.

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Differential growth rate between sexes was observed inthreadfin breams (Eggleston, 1973) and a possibility of such asituation occurring in.§. Japgnigus was also recognised inthis study. Investigations made with scales and otoliths didnot reveal growth checks of value in age determination in thisspecies (some otolith sections were prepared when the authorvisited Lowestoft laboratory, U.K., but growth check of usewere not discernible). As it was not possible to make lengthmeasurements of males and females separately in the field inthe absence of external sexual dimorphism and in view of thepractical difficulties in doing the work in the landing centre,the pooled data of males and females only were considered forestimating growth parameters.

7. Estimates of mortality, population size and yield per recruitof gemipterus japgnicus (Bloch) in the trawling groundsoff Kakinada.

For the first time in India, the mortality rates andstock size of yemipterus Japonicus were estimated on thebasis of data generated from comercially exploited populations;the earlier study by Krishnamoorthi (1978) was based on datafrom vessels conducting exploratory surveys. Using the lengthfrequency data obtained during 1976-79 from commercial trawlersat Kakinada and the values of growth parameters estimatedearlier (Murty, 1984 a), the mortality rates were estimatedand stock size determined. The values of total mortality rate(Z), fishing mortality rate (F) and natural mortality rate (M)were estimated as 1.86, 0.72 and 1.14 respectively. It was shown

that the exploitation of §. igpggigug during the period did nothave any adverse effect on the stock.

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8. Further studies on the growth and yield per recruit ofgemipterus Japonigus (Bloch) from the trawling grounds offKakinada.

Having studied (Murty, 1984 a) the growth using the modalprogression method and recognising the bottlenecks in relia­bly estimating the same using this method, another attempt toestimate the growth parameters of yemipterus Japonicus wasmade using the length data collected during 1980-'83 from offKakinada and following the less subJective'Integrated Method‘of Pauly (1980 a). The mortality rates, length at first captureand yield per recruit were also estimated. The von Bertalanffy

growth parameters estimated were L QC-= 339m, K-= 0.52 per yeart°= -0.16 year. The total (Z), natural (M) and fishing (F)mortality rates were estimated as 2.64, 1.11 and 1.53 respec­

tively. The length_at first capture (LC) was estimated as120 m. The yield per recruit was estimated and it was shownthat increased effort would result in decreased yield in thegrounds under exploitation, if the cod end mesh size was notchanged. It was also shown that yield could be increased if thecod end mesh size was increased by 70% without increasing theeffort.

The various issues relating to estimation of parameterswere discussed in detail and the need to update the estimates,whenever stock assessment was attempted, was indicated. Thevalues estimated in this work were compared with the earlierestimates.

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9. Present status of exploitation of fish and shellfish reso­urces - Threadfin breams- Monsoon fisheries of west coastof India, prospects, problems and management.

[“As Principal Investigator of the project on threadfinbreams, the author analysed the data collected bycolleagues working at different centres along thewest coast of India, interpretted the same, reviewedthe literature and prepared the paper for publication.Additionally, the author was associated with the edito­rial work of the publication_7

Due to the ban imposed by the government on trawlingduring monsoon period along the Indian west coast, particularlyalong the Kerala coast, the fishing industry expressed appre­hensions on the validity of such a ban. As part of the Insti­

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tute's efforts to examine whether such a ban was indeed nece­

ssary, the data on threadfin breams- a resource of consider­able magnitude taken in large quantities during monsoon periodby the trawlers- collected during 1984-'88 were analysed andthe results reported in this paper.

The data on total catch, species composition, length com­position of catch and maturity condition of fishes exploitedduring different seasons were examined critically. The studyrevealed that while the ban on trawling was not essential sofar as threadfin breams were concerned, the need for-continu­ous monitoring of the exploited stocks was emphasised because:the trawl fishery was multispecies in nature, the inshoregrounds were known to be nursery grounds for many species of

fin- and shellfish, the yields of threadfin breams in theinshore fishing grounds of 0-50 m depth range reached nearoptimum levels and because the cod end mesh size of trawl nets

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was reduced in the shrimp-oriented trawl fishery.

B. SILVERBELLIES

The silverbellies (Leiognathidae) are known to be abun­dant in shallower regions of the sea upto about 40 m depth(James, 1973: Pauly, l977 a, b; Pillai and Dorairaj, 1985;Sudarsan gt gls, 1988; Sivaprakasam.2t gl.,l991) though theyare known to occur in depths of 100-150 m.also (Sudarsan_g§ §l.,1988). An estimated 62304 tonnes of silverbellies were landedin India in 1993 (Anon,, 1994) which formed 5.5% of total deme­rsal fish catch and 2.7% of total marine fish landings of India.Maximum landings (71% of total silverbelly catch) of these fis­hes were obtained along Tamil Nadu coast, followed by AndhraPradesh (9%), Kerala (8.4%), Karnataka (6.0%) and other maritimestates. Though these fishes were taken by artisanal gear aswell as trawl, the latter accounted for the bulk of the landings.silverbellies were known to undertake diurnal vertical migrat­ions (Venkatraman and Badrudeen, 1974: Murty, 1988) stayingat the bottom during day time and rising to surface and sub­surface watersduring night time. A total of about 20 specieswere known from india but only a few species: Leiognathggjonesi, Q. bindus, Q. dussumieri, Q. and secutorbrevirostris

insidiator contribute to the fishery significantly.10. Observations on some aspects of biology of silverbelly

peiognathus b nd (Valenciennes) from Kakinada.y _i_ usLeiognathusigindus was one of the mst dominant components

of silverbelly catches along east coast where no attempt tostudy the biology was made. The present paper from Kakinada was

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the first one from this coast as the single earlier work(Balan, 1967) from the country was from the west coast ofIndia. The aspects of biology pertaining to maturation andspawning and length—weight relationship were presented in thispaper.

The length at first maturity (50% maturity) was estimatedas 80 mm. The ova diameter studies showed that Q was. bindus

a fractional spawner, each fish spawning twice during a year.

The spawning period was found to be continuous throughout theyear with peak during DecembereApril. The length frequencydistribution of the species in the fishery was presented. Thelength-weight relationship was calculated as:

Log w - -4.77709 + 2.96182 Log L

11. Studies on the growth and population dynamics of silversbelly Leiognathusybindug (Valenciennes) in the trawlinggrounds off Kakinada.

After completing a study of the spawning biology of

Leiggnathusybindus (Murty, 1983 a), the von Bertalanffygrowth parameters, mortality rates and yield per recruit wereestimated utilising the length frequency data collected fromthe trawl landings at Kakinada during 1979—'8l. This alsohappenned to be the first work from the east coast of Indiaas Pauly and David's (1981) estimation of growth parametersusing the data of Balan (1967), was from off Calicut (west

coast). The growth parameters were estimated as hx:= 158.4 mm,

K = 0.58 per year and t°= -0.024 year. The mortality rateswere estimted as Z=5.2, M=l.5 and F=3.7. The study on yield

per recruit indicated the need to increase the cod end meshsize by about 50% to be able to harvest the maximum yield

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without affecting the stock adversely.

12. Population characteristics of the silverbelly peiognathusbindus (Valenciennes) along west Bengal coast.

This paper was based on the data collected during amidwater trawl survey conducted between long. 200- 21° 03.8and lat. 87°15. - 88°55. E along the coast of west Bengal.The data on L. bindus during the survey showed that largerfish inhabit relatively deeper waters and, confirmed theearlier study of Venkatraman and Badrudeen (1974) that silver­bellies stay at bottom during day time and migrate to surfaceand subsurface waters during night. The length-weight relation­ship of the stock was estimated as Log W= -5.38217+3.28637 Log LThe mortality rates estimated showed that total mrtality ratewas equal to natural mortality rate indicating that there wasno exploitation of this species in the region: this was supp­orted by the landings also. It was suggested that maximum yieldof this species could be obtained at a fishing mortality rateof 3.6 with the 42 mm cod end mesh size of trawl net.

13- Biology and population dynamics of the silverbelly"Beggtor insidiator (Bloch) from Kakinaua.

In the silverbelly landings by commercial trawlers atKakinada secutor insidiator was one of the most dominant. f h '.§,.__ :____'_'f_.7" H ' iii’­

species. On the basis of data collected during 1979-'83,a study on the biology and population dynamics of the exploitedstock was made. This happenned to be the first report on theabove aspects of the species from India; earlier, Pillai(1972), briefly dealt with the spawning habits and fecundityof this species from Tuticorin.

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Maturation, spawning and sex ratio were studied and itwas shown that this species spawned throughout the year witha peak during January~March in the sea off Kakinada. Thelength at 50% maturity was estimated as 90 mm. Though themaximum length of males and females was the same, femaleswere predominant in larger lengths. The length—weight relationship was calculated as Log w= -5.73713 + 3.43654 Log L.

The von Bertalanffy growth parameters were estimated as

L“? 123 mm, K= 1.2 per year and t°=--0.01 year.)

The total mortality rate was estimated using different­methods and the value was taken as 6.1052. Similarly, thenatural mortality rate was estimated by four different appro­aches as 1.8, 2.3, 2.4 and 2.6. The age at first capture wasestimated as 0.86 year. Using all these values, the yield perrecruit was estimated. The yield as a function of fishingmortality showed that it did not attain maximum within thevalues of F considered. The yield as a function of age at

first capture (to) indicated the need to reduce the tc from0.86 to 0.70 year. The reduction in tc was, however, not recomended because the same would result in increased exploitat­ion of still smaller fishes which did not have any commercialvalue.

The difficulties encountered in the analysis of datafor estimating growth parameters, mortality rates-and yieldwere discussed.

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C. CROAKERS

The fishes of the family Sciaenidae (croakers, jew fish)represented over thirty species in India, contributed signi­ficantly to the exploited demersal finfish resources of thecountry. In 1993, an estimated 161105 tonnes of croakers werelanded along the Indian coast (Anon., 1994) which formed about14% of total demersal fish catch and 7% of total mrine fishlandings of India. Maximum catches were obtained from Gujarat,followed by Maharashtra, Tamil Nadu, Orissa, Andhra Pradesh,

Kerala and other maritime states. of the species known from the

¢°\""=1'Y- Prstseibss 9£s¢s=1fl3P§- Qtslithvs 9‘!!1§!~T:1- -Jsmise

!29l2££@42- m€E£2FhXQ¥§',£' an°“5= E‘ §i22'.Q~ carutta andI \

Atrobpcca nibe were most abundant at different regionsasome species like Q. dlacanthqs which used to form dominantcomponents in the landings along north west coast of India,registered declining yields in recent years.

14. Observations on some aspects of biology of the black cro­aker.§trobnpca nibg (Jordan and Thompson) from Kakinada.

The paper represented the second report on biology of

gtrobuccg gibe from anywhere in the world and the first onefrom Indian Ocean region in general and from the Indian coastalwaters in particular: the only earlier report was from Japan(Matsui and Takai, 1951).

Q, gigg formed a seasonal but major component in themnltispecies (about 20 species from off Kakinada) sciaenidcatches taken off Kakinada by trawlers: during 1975~'77,this species formed 27% of the average annual sciaenidcatch of 1500 tonnes. The length-weight relationship was

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estimated as Log W = -5.524308 + 3.213476 Log L. The lengthat first maturity was estimated as 145 mm; through the studyof ova diameter frequency distribution, it was shown thatQ, nibe spawned twice during the spawning period which exte­nded from February to July in the sea off Kakinada.

15. observations on some aspects of biology of the croakersQohnius (QohnieoB§)_QussuQieri (Cuvier) and Johnius( ) Bloch from.Kakinada.Johnius carutta

This paper was the first report on the biology ofQ. Qussumieri and Q. carutta (excepting the study on spawningof Q. by Rao, 1967) from the Indian seas. The lengthQarutta

weight relationship, relative condition factor, length atfirst maturity, spawning habits and spawning seasons were

determined. In Q. Qgssunigri, the spawning season extendedfrom March to August. The length at first maturity was esti­mated as ll0 mm. The length-weight relationship was calculatedas Log W = —4.845l1 + 2.96347 Log L. The changes in relativecondition factor were found to be associated with gonad cycle.

In Q. ca t a, the length at first maturity was found toru tbe 155 mm. The spawning season extended from January to June.

The length-weight relationship followed the equationLOg W a + LOg L016. Growth and yield per recruit of Johnius (Johnius) carutta

Bloch in the trawling grounds off Kakinada. A

After studying the maturation, spawning, length-weight

relationship in Q. (Murty, 1984 b), the estimationcaruttaof growth parameters, mortality rates and yield per recruitwas made on the basis of data collected from trawl landings

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at Kakinada during 1980—'83. The parameters of growth were

estimated as bX:= 333.3 mm, K = 0.44 per year and toe —0.0002year: the mortality rates as Z I 5.07, M = 1.0 and F = 4.07.At the prevailing levels of to and F during 1980-83, theyield per recruit as a function of F had already declined.The yield per recruit as'a function of tc showed that Ymaxcould be obtained at tc= 1.7. The study lead to the suggestionof the following options to maximise and then sustain the yield:——-——-to decrease the fishing effort by 51% without modifying

the cod end mesh size,to increase the age at first capture by 50% (i.e. codend mesh size) without changing the fishing effort, or

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————— to increase both effort and cod end mesh size of trawlnet 0

17. Observations on some aspects of biology of Johnius(gohniegps) vogleri (Bleeker) and Rennahia macrophthalmus(Bleeker) in the Kakinada region.

['The author was responsible for planning the work,collection, analysis and interpretation of dataand for preparing the paper for publication. Thejunior author rendered assistance in aquisitionand analysis of data.7

Among the several species contributing to the sciaenidfishery by trawlers at Kakinada, Johnius vogleri and Pen a ia_______ n hmacrophthalmus were important among others. From.off Kakinada,there was no information on the biology of these species; inthe case of Q. ggglggi, there was no information on the biologyfrom east coast of India. The earlier studies were restricted

to those by Rao (1967, 1983) in Q. macrophthalmus from Visakha­

patnam and by Muthiah (1983) in.Q. vogleri from off Bombay.The present paper dealt with the results of a study on the

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length-weight relationship and spawning biology. It was shwnthat these two species spawn in two batches during 0ctober/November-June in the sea off Kakinada. The length at firstmaturity (50% maturity) was estimated as 147 mm in §_ ­. macro

'phthalmps and 190 mm in‘Q. vogleri. The length—weight relatio­nship was estimated 888

Q. macro hthalmns: Lo W = -4 63735 + 2 89703*_ 7 P L_iifi_ g 0 0Q. vogleri: Log w = -s.0s923 + 3.07931 Log L

The fishes of the family Carangidae comprising of horsemackerels, scads, leather jackets and others, constitute animportant pelagic finfish resource of India represented bynearly sixty species belonging to about16 genera. In 1993,an estimated 129064

(Anon., 1994) whichtonnes of carangids were landed in Indiaformed 11.3% of pelagic finfish catch

and 5.6% of total marine fish landings of India. of the diffe­rent species, the scads represented by about four species cont­ribute to over 46% of the carangid catches. Degapgggggis the most dominant species of thelarge quantities by

18. Observations ondynamics of the(Carangidae) in

In the catchesKakinada, the scad,

russelliscads and is exploited in

trawlers during certain periods.

some aspects of biology and populationssssslli <R“PPe11>

the trawling grounds off Kakinada.scad Qgcapterus

of carangids landed by the trawlers atQecaptergs rpsgelli accounted for over

80% by weight of the carangid catch, with an estimated averageannual catch of 1229 tonnes during 1979-83. In view of thelack of information on biological characteristics (excepting

22

the work of Sreenivasan, 1982, 1983, 1984 from Vijhinjamalong the south-west coast of India) and population dynamicsof the exploited stocks along Indian coasts, an investigationinto these aspects was made using the data collected during1979-83.

The annual estimated catches and catch rates and seasonal

variations in abundance were presented. Q. 8 supportedrussellia seasonal fishery with major peak during Januaryemay periodand a minor peak in September.

B

I

The length-weight relationship followed the equation:Log w = -5.93433 + 3.40764 Log L. The von Bertalanffy growth

parameters were estimated as Ldzn 232.3 mm, K = 1.08 per year

and t°= —0.08 year. The length and age at first maturity wereassessed as 150 mm and 0.88 year respectively. The spawningperiod off Kakinada was determined as extending from.Decemberto.August. The different mortality rates were estimated asZ = 6.65, M = 1.90 and F =-4.75, The yield per recruit ana­

lysis showed thatiif the age at first capture was above 0.6year, the yield increased with increase in F without attainingmaximum.

studying the earlier literature on experimental fishingand taking into account the fishing practices, the possiblereasons for the seasonal fishery of Q. were explained.russelliThe spawning season determined was explained to be realistictaking into account the earlier studies on exploratory andexperimental fishing and larval and spawner surveys (Rao et al Qiii1977) and the review of Qasim (1973) on spawning of Indianmrine fishes. The reasons for the difference in the estimated

23

values of growth parameters given by Sreenivasan (1983) andthis study were examined and explained, though it was expre­ssly stated that these values could be different in differentstocks of the same species and also innthe same stock betweendifferent periods (vide, Gulland, 1983) for various reasons.

In the estimation of natural mortality coefficient, theavailable methods, including the methods recently developed(Pauly, 1980 b, 1983; Alagaraja, 1984) were critically exa­mined and finally the method adopted by Sekharan (1975) wasfollowed with Justification.

The problem of estimating length at first capture (LC),in the absence of selection experiments, was discussed andjustification deduced for the estimate obtained taking intoaccount the known distribution pattern of the species andfishing practice. Yield per recruit analyses were, however,

made using different values of LC (and hence to) and theyield curves compared and the strategy of exploitationsuggested noting the limitations.

24

PART III MIXED FISHERIES ASSESSMENT_ V 7'“7" V _'t , , '—_ , '_,___‘—_“;__ _:___I‘_‘Il'7T:L _"‘——‘_ i‘ ‘I “ _ ]‘—_—_ ‘ f

19. Multispecies stock assessment with particular referenceto major demersal fish species in the trawling groundsoff Kakinada,

The Indian marine fisheries, like any comparable tropicalmarine fisheries, exploit a large number of species in any

lQ .'gear. The classical models of fish stock assessment ofexploited stocks (Beverton and.Holt, 1957) only deal withsingle species assessments. The author made a few singlespecies stock assessments and found that though such assess­ments did provide useful insights into the state of the expeloited, single species stocks, they did not help to palnninga strategy for rational exploitation and management of multi­species stocks. Besides, methods of assessing multispeciesstocks in the tropical context were also not available. Theauthor, therefore, attempted the multispecies stock assess­ment using the data obtained from trawl landings at Kakinada,This was the first attempt in India to do multispecies stockassessment and it primarily demonstrated the methodologyusing four demersal finfish species. The theoretical andpractical issues, in making the assessment, were discussed

in deta.;i1 0

In the higher latitudes, particularly in the north sea,multispecies stock assessment model (nultispecies VirtualPopulation.Analysis Model-—-MSVPA) was developed (Helgason

and Gislason, 1979; Gislason and Helgason, 1985; Pope, 1979:

25

ICES, 1984, 1986, 1987: Gislason and Sparre, 1987) takinginto account the species interactions, particularly in regardto mortality generated by predation, and following theage-based methodology. While this approach was still under

trial, in the tropics, the age—based methodology could not beimplemented because of the inability to determine the age ofindividual fish (even after the discovery of daily growthrings in the otoliths of tropical fishes, as this methodologywas not successful in ageing fishes older than about oneyear-——— see Gjosaeter g§y§l,, 1984). Necessarily, therefore,the length-based methodology appears to be the only answerto tropical fish stock assessment until a more efficient

\

model is developed.

In the present paper, the methodology of multispeciesassessment using the data of one speices of threadfin breams,one species of croakers and two species of silverbellies,using the Beverton-Holt model was demonstrated. It was alsoshown that with existing gear under operation, the efforthad to be reduced by about 6% to ensure maximum yield of thefour species or, the cod end mesh size had to be increased byabout 28% without increasing or decreasing the effort. Thelatter option was explained to be the most desirable one asthe lengths at first capture of the species were less thanthe lengths at 50% maturity.

20. Mixed fisheries assessment with reference to five impor­tant demersal fish species landed by shrimp trawlersat Kakinada.

After attempting an assessment of multispecies stocksin the tropical context, another assessment of five exploited

26

species in the sea off Kakinada was attempted using thelength-based Thompson and Bell analysis developed bySparre (1985). This approach, similar in concept to the oneattempted earlier (Murty. 1987 b), was also given primarilyto demonstrate the methodology for assessment of a miredfishery. Additionally, this approach considered pooling thevalues (prices) instead of the yields themselves so that itbecame more meaningful in the mnagement. The theory oflength-based Thompson and Bell (1934) model was also presented

This was the first stock assessment study of the kind intropical waters and it was shown that this approach could befollowed for the assessment of a large number of species exp­loited by the gear.

21. Stock assessment of threadfin breams (gemipterug spp)of India.

[7As principal Investigator of the project and teamleader, the author analysed the data supplied bycolleagues from all centres and interpretted thesame, reviewed the work done and prepared thepaper for publication, in: addition to generatingdata from Kakinad§7

Though some isolated attempts on stock assessments weremade,during different periods from different localities, ofsingle species (Krishnamoorthi, 1978: Murty, 1983 b, 1987 a;

Vivekananda? and James, 1986; Devaraj and Gulati, 1988;.John,1989: Kasim_§t_gl., 1989), concerted efforti to study thepopulation dynamics from all along thea coast taking intoaccount the principal species, was not made. This paper dealtwith the mixed fisheries assessment of the threadfin breams

27

wsairssxrs Japonisvs and E» mss¢;>ri<>s> from east and "estcoasts of India. All necessary parameters were estimated,stock assessment made and optimal yield levels in the exist­ing fishing grounds indicated. The various scientific_issuesrelating to the assessments in the tropical context usinglength data were discussed, particularly the widely-differingvalues of growth parameters estimated using data of differentyears and the consequent'difficulty in using_g particular setof growth parameters for estimating mortality rates and yield.The choice of selecting two sets of values of growth parameters,

the smallest and largest gxivalues and their related K valuesfrom among the several sets of reasonably satisfactory valuesobtained, for proceeding further with the assessments and thenconsidering the average values of yields (of the two obtainedusing two sets of growth parameters) corresponding to eacheffort level (F-level) as representing the realistic estimates,was believed to be the best under the existing situation.Besides, the conflicting options for rational exploitation ofdifferent species in the same fishery were pointed out and thestrategies to be followed, in the given option, were indicated.

22. Stock assessment of silverbellies of India with particularreference to.Andhra Pradesh and Tamil Nadu.

['In addition to generating data from Kakinada, asPrincipal Investigator of the project and teamleader, analysed the data from all four centresand interpretted the same, reviewed the work doneand prepared the paper for publication‘?

Though silverbellies were known to occur in the catchesall along the Indian coast, about 80% of the silverbelly catch

28

was landed from off Tamil Nadu and Andhra Pradesh: of these

regions, Tamil Nadu's contribution was the highest forming70% of silverbelly landings of India. Bulk of the silverbellycatch in the country was obtained from trawlers.

Of the species contributing to the fishery, geiggnathugbindus and §e§uto£ insidiator were the most dominant alongAndhra Pradesh and northern Tamil Nada coasts and_§. jonesiand Q. Qussumieri along southern Tamil Nadu coast.

Though work on stock assessment of silverbellies was

carried out earlier (Venkatraman gt 35., 1981: Murty, 1986,1988, 1991 and .Karthikeyan g§_§l., 1989), it was restrictedto single species from restricted areas. T0 have an overallview of the status of the exploited silverbelly stocks fromthe region of greatest abundance in the country, two mstdominant species (Q. bindus and §, ingidiator) from AndhraPradesh and Northern Tamil Nadu and two other dominant species

(Q. jonesi and Q. dugsumigri) from southern Tamil Nadu wereselected for the present assessment.

The available information on the biology of differentspecies from different localities along the Indian coast wasreviewed. Parameters of growth and mortality rates of theselected species were estimated. Stock assessment was done foreach species separately from the regions and then mixed fisher­ies assessment was carried out. Along Andhra Pradesh, the effortleveli was found to be greater than the one yielding maximumcatch in the existing fishing grounds: in northrn Tamil Nadu,scope for marginally increasing the yield by increasing theeffort was indicated.In southern Tamil Nadu also, scope forincreasing the yield bv increasing the effort was indicated.Regulation of cod end mesh of trawl net was also explained.

29

PART IY RESOURCES SURVEY AND MANAGEMENT

23. Resources of ornamental fishes of the Lakshadweep islands

['The resources survey was carried out by threeteams covering thirteen islands. The authorparticipated in the first team. The responsi­bility of analysing the data and preparationof paper on ornamental fishes was given tothe author who analysed the data and preparedthe paper for publication, using the datacollected by the second and third teams also;7

A

In recent years, the demand for live ornamental fishesis increasing and a strong export market is developing.Though a comprehensive account of the fishes of Lakshadweep(Jones and Kumran, 1980) was published, information on spec­ies available for exploitation, their relative abundanceand the areas of abundance in the lagoons and reef flats ofdifferent islands was lacking. For the first time in the region,a survey was conducted during January—March 1987 in 13 islands

of Lakshadweep, which resulted in collection of 139 speciesof ornamental fishes belonging to 33 families. Of these,it was shown, the fishes of the family Pomacentridae werethe most dominant in terms of numerical abundance and number

of species (22 species collected) followed by 'Labridae(21 species). Apogonidae (10 species), Mullidae (9 species),Chaetodontidae (8 species), Callyodontidae (6 species),Acanthuridae (6 species) and others. The number of speciesknown from Lakshadweep region and the number of species comon

in the area were given. The distribution and abundance of diff­erent species of ornamental fishes in the reef flats and lagoons

30

during the survey period were explained and a few suggestionsfor rational exploitation were made.

24, Present trends in marine fisheries management andcatch forecasting,

[TA£ter discussion on the subject and the formatof the paper, the responsibility of survey ofliterature, consolidation of informtion andpreparation of the paper was taken by this author?

The Indian marine fisheries were facing a near crisisin that, the catches from the presently exploited inshorewaters reached optimal levels in respect of majority ofstocks and the region beyond 50 m depth in the Exclusive

\

Economic Zone which was estimated to support a potentialyield of 1.7 million tonnes, was yet to be exploited commer­cially. While technologies for increasing production from theseas were available and the investigations on several exploi­

ted stochs were carried out aiming at stock assessment, itwas felt necessary to bringout a comprehensive account of theavailable methds of marine fisheries management and catchforecasting under the Indian context and to make suggestionson the future course of action to be taken. After describingthe current marine fisheries scenario briefly, the variousmethods of short and long term forecasts of the yields, themanagement strategies and the information requirements wereindicated,

31

25. complexities of management of inshore fishery resourcesof India.

[“The author was involved in the preparation andfinalisation of the paper;7

In the context of declining yields from the inshorefishing grounds along the Indian coast, the prevailing socialand economic conditions of the resource users and the various

complexities, controversies and conflicts among the different

sectors of fishing industry in the country, the imperativeneed to enforce regulations and manage the fisheries wasdiscussed. In consideration of the various issues, it wassuggested that:

-—- increased role might be provided to the local orregional fishing communities in the formulationof regulatory measures and their managerialresponsibilities,

—-—- positive access might be ensured in favour oflocal fishing communities,regulatory measures should be formulated witha strong conservation policy through carefulregulation of fishing effort and restrictionson gears, anda system of fishing within the regional managementscheme transmuting the conflict to coexistenceor even symbiosis might be incorporated in themanagement system.

32

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