An assessment of ring seine fishery in Kerala through surplus production model

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1 Indian J. Fish., 54() : 35-40, Ap.-Jun., An assessmen of ing seine fishey in Keala hough suplus poducion model K. ALAN AND T. V. SATHIANANDAN* Cenal Maine Fisheies Reseach Insiue, Cochin , India *Madas Reseach Cene of CMFRI, Chennai , India ASTRACT Ouboad ing seine is one of he majo geas opeaed in Keala which conibues abou 37% of he oal landings in he Sae. Oil sadine (Sadinella longiceps) and Indian mackeel (Rasellige kanagua) ae he wo species ha accoun fo abou 84% of he ing seine cach. The ing seine fishey began in he Sae by mid eighies and gown ino a majo fishey ove he yeas. An assessmen of he ing seine fishey in he sae hough nonequilibium suplus poducion model was made in his sudy by using ime seies daa on cach and effo of ing seine in Keala duing An index of elaive biomass a and an index of ne poducion ae m wee compued, apa fom fishing moaliy aes F, maximum susainable yield (MSY), effo coesponding o MSY and biomass coesponding o MSY. Resuls evealed ha he ing seine fishey in Keala is close o he sae of equilibium. ehaviou of m and F wee almos simila showing chaaceisics of fully developed fishey and he paen of hei diffeence m -F indicaed ha he saus of ing seine fishey in Keala is close o he opimal level a pesen. Inoducion The inoducion of ouboad moos o he adiional cafs, in he ealy eighies made conspicuous impac on he maine fisheies seco in Keala (alan e al., 989). Wih he inoducion of ouboad moos, he eswhile boa seine unis wih 5-8 cew membes wee eplaced by he ouboad moo fied, lage sized plank buil boas enhancing he cew capaciy o Mooizaion helped he developmen of innovaive high caching geas like ing seine on pa wih puse seine. Ring seines wee fis epoed duing in he Alleppey egion and picked up fas o he cenal and nohen Keala (alan e al., 989). The ing seine, a majo gea used in Keala is a fine meshed encicling ne used mainly o haves pelagic fishes like oil sadine and mackeel and conibued o.4% of he maine fish landings of Keala in 994 (alan and Andews, 995). Ove he yeas, is shae inceased and aained a level of 36.7% duing The size and CPUE of ing seine had changed ove yeas (Edwin and Hidayanahan, 998). The impac of ing seine and miniawles used in he aisanal fisheies in Keala was

2 K. alan and T. V. Sahianandan 36 examined by D cuz (998) and epoed as hamful o he fishey. Vijayan e al. (000) ecommended ouboad engines wih less han 50 hp engine powe fo effecive opeaions of ing seines. Oil sadine (Sadinella longiceps) and Indian mackeel (Rasellige kanagua) ae he wo species ha accoun fo abou 84% of he ing seine cach. Fom 990 onwads, abou 75% of he oil sadine landings and abou 60% of he mackeel landings in he Sae ae fom ing seine opeaions. In he pesen sudy an aemp is made o assess he saus of oil sadine and mackeel socks off Keala coas using ime seies daa on cach and effo of ing seines in he sae by fiing nonequilibium suplus poducion model and a linea vesion of he model suggesed by Schaefe (954). Maeials and mehods Time seies daa on ing seine cach in Keala and effo expended in ems of hous of opeaion of ing seines duing obained fom he Naional Maine Living Resouces Daa Cene (NMLRDC) of he Cenal Maine Fisheies Reseach Insiue, Cochin was used fo he sudy. The model used is he nonequilibium suplus poducion model (Schaefe, 954) given by d d ( F () K = ) This leads o he calculaion of biomass as α exp( α ), α 0 α + (exp( ) ) β α + = (), α = 0 + β whee β =, α = F and K HeeF is he fishing moaliy ae, f is he fishing effo, K is he caying capaciy, is he ininsic ae of incease of he sock, is he biomass a ime (yea) and q is he cachabiliy coefficien. ased on his model, yield is calculaed as F β ( exp( α )) ln, α 0 β α Y = (3) F ln[ + β ], α = 0 β Paamees of his model o be esimaed, using he ime seies daa on cach and effo, ae (i) he iniial biomass 0, (ii) caying capaciy K, (iii) ininsic gowh ae and (iv) cachabiliy coefficien q. Fo esimaion of hese paamees, he mehod suggesed by Wang (00) was adoped. A bief ouline of his pocedue is pesened below. a) The cach pe uni effo (suiably scaled) U is fis calculaed, which is an abundance index of aveage biomass a yea. b) The abundance index is calculaed a he beginning and end of yea as = ( U + U ) / and ( ) / + = U + U + especively. c) Using he deived equaion qk q K U = qk + ln( ) X and eplacing + ln( ) wih ln( ) + +, esimaes of and q ae obained hough a egession of U on ln( ) + and X, whee X is he effo. d) Fo esimaion of K, an index of elaive biomass, a, which eflecs he flucuaions of elaive biomass yea afe yea, having he q expession a = + ln( ) X + is calculaed fo diffeen yeas.

3 Assessmen of ing seine fishey 37 xp( a F) ) Coefficien of Vaiaion (CV) of hese quaniies fom iniial yea onwads is woked ou fo diffeen peiods and he peiod wih minimum CV is used o calculae he aveage of hese quaniies as a. e) The iniial biomass is calculaed using he iniial yea s yield Y and coesponding fishing moaliy F = qx, whee X is he effo, as and K is esimaed as. f) The ne poducion ae defined as is calculaed o sudy he cuen saus of fish socks unde exploiaion. The fishing moaliy is calculaed as. g) Unde fishing, successive peiods biomass has he elaion m F = m F + e o e = (4) + Equaion (4) is he aio of successive yeas biomass and he aim should be o keep his aio close o uniy so ha hee is no much change in he biomass ove ime. This happens when m - F is close o zeo. Thus, he diffeence beween m and F povides he cuen saus of he fish socks unde exploiaion and he goal of fishey managemen is o make his diffeence as small as possible. A final esimae of he fou paamees was aived a hough ieaion by minimizing he quaniy [ log( Y ) log( ˆ )] Y. Esimaes of maximum susainable yield (MSY), biomass a MSY level, fishing moaliy ae a MSY level and effo a MSY level wee calculaed as given below (Page, 994). ˆ ˆ K ˆ MS Y = ; 4 ˆ ˆ K MSY = ; ˆ ˆ F MSY = ; f MSY ˆ q ˆ ˆ = (5) The linea vesion of he model aemped is y = a f b f (6) whee f is he effo and y is he yield. The paamees a and b of his model was esimaed hough egession and he MSY and coesponding effo, f MSY based on his model wee calculaed using he following fomula. aˆ aˆ MSY = 4bˆ ; f MSY = b ˆ (7) Resuls and discussion The ime seies on cach (in onnes) and effo (in hous of opeaion) by ing seine in Keala duing he peiod ploed ae shown in Fig.. The final esimaes of paamees of he models aemped and esimaes of maximum susainable yield (MSY), biomass a MSY level and opimum effo ae given in Table. The flucuaions in he index of elaive biomass a ae shown in Fig.. Values of his index anged beween 0.6 in 993 and 0.95 in 987. In he ealy yeas, fom 986 o 993, his index showed a deceasing end indicaing ealy developmen of he ing seine fishey. Fom 994 onwads, a anged beween 0.66 and 0.77 having 0.7 as he aveage. Fom Fig.3, i can be seen ha boh m and F behave in almos simila manne evealing hei dependence which geneally is a chaace of fully developed fishey. In he las five yeas m F e, which is he aio he quaniy of biomass in consecuive yeas vaied beween 0.97 and.064 wih.03 as he aveage, vey close o uniy. This indicaes ha he biomass of he esouces havesed by ing seine does no change much ove yeas. Thus he ing seine fishey in Keala is vey close o he sae of equilibium and hence he socks of he wo esouces, oil sadine and mackeel, mainly havesed by ing seine ae no unde sess. The ne poducion ae m anged

4 K. alan and T. V. Sahianandan 38 Cach (onnes) / Effo (hous) Cach Effo Yea Fig.. Cach (in onnes) and effo (hous of opeaion) fo ing seine fishey in Keala duing a Yea Fig.. The index of elaive biomass a fo ing seine opeaions in Keala.5 F m F & m Yea Fig. 3. Ne poducion ae m and fishing moaliy ae F fo ing seine opeaions in Keala beween 0.3 in 987 and in 993 and he aveage was The biomass coes-ponding o he highes ne poducion ae is,43,500. and he coesponding fishing moaliy was Since he biomass having maximum ne

5 Assessmen of ing seine fishey 39 TALE : Esimaes of paamees of (a) nonequilibium suplus poducion model and (b) linea vesion of Schaefe s model, fied using he ing seine cach and effo daa of Keala Paamee Esimae (a) Nonequilibium suplus poducion model Iniial iomass, Caying Capaciy, K Cachabiliy coefficien, q e-06 Ininsic ae of incease, Maximum Susainable Yield, MSY 6379 iomass a MSY level, MSY 9767 Fishing moaliy a MSY level, FMSY Effo a MSY level, f MSY 8469 h of opeaion pe annum (b) Linea vesion of Schaefe s model y = a f b f Regession R Esimae of inecep, â Esimae of slope, E-07 Maximum Susainable Yield, MSY 649 Effo a MSY level, h of opeaion pe annum poducion is consideed as he bes densiy of he sock (Wang, 00), he saus of he socks exploied by ing seines (mainly oil sadine and mackeel) ae consideed as he bes in 993. Fishing moaliy and he ne poducion ae ae nealy equal in his yea. The aim of fishey managemen is o bing hese indices vey close, o keep he aio of biomass in consecuive yeas o uniy. I can be seen ha fom 997 onwads he diffeence of m -F is posiive (excep in 999 and 003) and close o zeo which is an indicaion ha he saus of ing seine fishey in Keala is close o he opimal level a pesen. If his diffeence coninues o go below zeo in he coming yeas, hen hee is need fo concen o bing i above and close o zeo by educing he effo. The maximum susainable yield was esimaed as,6,379 wih.74 as he coesponding fishing moaliy and 8469 h. as he opimum annual effo. iomass coesponding o his level of yield is,9,767. The esimae of MSY and f MSY obained using equaion (7) fo he model (6) was,6,49. and h. especively. This model canno yield esimaes of biomass and fishing effo. Duing he las five yeas, he aveage cach by ing seines is,6,64. and is aveage effo is h. pe annum. This is below he MSY level obained using he nonequilibium suplus poducion model and o each up o he MSY level, he level of effo have o be doubled (Table a). Doubling of he pesen effo will a he mos esul in incease of cach by only aound 0,000. and hence i is no economically viable and feasible. A bee managemen opion is o allow he pesen level of exploiaion by ing seines and monio he m -F diffeence and sugges educion in ing seine effo if his diffeence coninues o fall below zeo consecuively in he coming yeas, o bing i above bu close o zeo.

6 K. alan and T. V. Sahianandan 40 Acknowledgemens The auhos ae gaeful o D. M. Sinah, Head of Fishey Resouces Assessmen Division fo poviding he daabase fo his sudy. We ae also gaeful o D. Mohan Joseph Modayil, Dieco, Cenal Maine Fisheies Reseach Insiue fo he suppo. Refeences alan, K., K. K. P. Panikka, T. Jacob, Joseph Andews and V. Rajendan 989. Mooizaion of couny caf in Keala An Impac Sudy. CMFRI Spl. Publ., No.45. alan, K. and Joseph Andews 995. Maine fish poducion in Keala esimaion pocedue and pesen end. In: Poceedings of Fish Resouces in Indian EEZ and Deep Sea Fishing. p. 3-40, P.U. Vaghese (Ed.). D Cuz, S. Tio 998. The Ring Seine: Evoluion and Design Specificaions. SIFFS: Tivandum. Edwin, L. and C. Hidayanahan998. Cach pe uni effo (CPUE) of ing seines of souh Keala coas. Symposium on Advances and Pioiies in Fisheies Technology, Sociey of Fisheies Technologis (India), -3 Febuay, Cochin, India. Page, M. H A suie of exensions o a nonequilibium suplus-poducion model. Fish. ull., 9: Schaefe, M Some aspecs of he dynamics of populaions impoan o he managemen of he commecial maine fisheies. ull. Ine-Ame. Top. Tuna Comm., (): Vijayan, V., L. Edwin and K. Ravindan 000. Consevaion and managemen of Maine Fishey Resouces of Keala Sae, India. Naga, The ICLARM Quaely, 3. Wang, C. H. 00. Esimaing he populaion paamees, q, and K based on suplus poducion model. 5h SCT meeing, July -7, 00, Honolulu, Hawaii. SCT-5 woking pape, AL-7,9pp. Dae of Receip : Dae of Accepance :

Sections 3.1 and 3.4 Exponential Functions (Growth and Decay)

Sections 3.1 and 3.4 Exponential Functions (Growth and Decay) Secions 3.1 and 3.4 Eponenial Funcions (Gowh and Decay) Chape 3. Secions 1 and 4 Page 1 of 5 Wha Would You Rahe Have... $1million, o double you money evey day fo 31 days saing wih 1cen? Day Cens Day Cens