ISSN X. tlon SERVICE

Transcription

1 ISSN X tlon SERVICE

2 THE PRESENT STATUS OF COASTAL TUNA FISHERY AT VIZHINJAM, TRIVANDRUM COAST G. Gpakumar and F.S. Sadasiva Sarma Vizhinjam Research Centre f CMFRI, Vizhinjam Intrductin The castal tuna fishery f Kerala, which has been yielding abut 6, tnnes annually in recent years, cnstitutes 32% f the ttal tuna landings f the cuntry. A district-wise analysis f the tuna prductin during 1979-'81 indicated that 7% f the ttal tuna landings in the state was frm the casital fishery alng Trivandrum district. At Vizhinjam, where fishing ges n all thrugh the year, castal tunas cnstitute a majr pelagic fish resurce accunting fr 2% f the ttal marine fish landings. Since the prime requirement f tuna fishery develpmsnt in the area seems t be the imprvement f the existing small-scale fishery sectr, knwledge n the present status f the fishery appears t be a basic necessity fr the planning f further develpment in this sectr. In additin, when the fishery harbur under cnstructin at Vizhinjam becmes peratinal, mechanised fishing fr tunas is bund t increase in the area and this als requires infrmatin n the catch trend and seasns f abundance f varius species fr the management f fishing fleet. Fishing gear and craft The chief gears emplyed fr tuna are drift net and hks and hnes which are perated either frm catamaran r dugut cane. Frm 1983, intrductin f traditinal crafts fitted with utbard mtrs started gaining mmentum in the small-scale fishery sectr at Vizhinjam. Of late, the gears fr tuna are mainly perated frm fibre-glass cated plywd built bats f abut 5.5 m OAL with utbard mtis. Cnsequently, the effrt f nn-mtrised traditinal crafts declined cnsiderably. The area ffishingfr mtrised crafts was abut 2-25 km ff Vizhinjam at a depth range f 6 t 8 m and that f nn-mtrised crafts was cnfined t abut km frm the shre at a depth range f 4-5 m. In this study, a fishing trip was taken as a unh f effrt and since bth the gears emplyed were fund t be almst equally effective fr catching tuna, n attempt was made t standardise the trips emplying different gears. Annual prductin The annual tuna catch and the ttal fish catch during 1983-'87 are given in Fig. 1. The catch ranged frm 472 t in 1983 t 2,37 t in 1985 with the annual average at 1,41 t. The year-wise percentage f tuna catch in relatin t ttal catch and the catch' per trip f tunas is shwn in Fig. 2. It is seen that the percentage cntributin f tunas in the ttal fish catch ranged frm 7.3 in 1983 t 21.6 in 1987 and averaged t The annual catch f tunas per trip varied frm 4.8 kg in 1983 t 24.8 kg in A marked increase in the catch as well as the catch rate f tunas was evident frm 1984 nwards. LUb s& X (J) 52 P TOTAL CATCH TUNA CATCH- N3- ID t r^ CD Fig. 1. Year-wise ttal fish catch and tuna catch at Vizhinjam during 1983-'87.

3 ^ Fig. 2. Year-wise percentage f tuna in the ttal fish catch and catch per effrt (C/E) f tuna in kg during 1983-'87. Seaianal pattern f tuna fishery The mnth-wise tuna catch, effrt and catch pei unit effrt based n pled data during 1983-'87 are shwn in Fig. 3. The average mnthly catch varied between 7. t in February t 23.4 t in Octber with the mnthly average at t. The catch per trip OTHER FISHES?^ TUNAS mm 24 2 {516 z il2 5 8 < 4 J F M A K J J A S O N D Fig. 3. Mnth-wise average catch (tnnes), effrt and catch per effrt (C/E) in leg f tunas during 1983-'87. /} 22Q: e LJ < ^ 8"Q QC CO ranged batween 9.9 kg in February t 22.8 kg in Octbsr with an verall mnthly catch pir trip f 15.6 kg. The pjak iiihing seasns were May and Septjmbsr-Nvember perid. Gear-wise prductin As generally understd, drift nets and hks and lines are nt perated fr tunas alne. The parcentage f tuna catch in the ttal fi>h catch brught by the gears perated frm mtrised and nn-ratrised crafts is Fig. 4. Percentage f tunas and ther fishes in different gears during 1983-'87. (A) Drift net (nn-mtrised craft), (B) Drift net (Mtrised craft), (C) Hks and line (nn-mtrised craft) and (D) Hks and line (mtrised craft). given in Fig. 4. Mtrised crafts brught better prprtin f tuna catch. It is seen that 53.5 % f the catch brught by hks and lines perated frm mtrised crafts and 39.1 % f the catch brught by drift net perated frm mtrised crafts were tunas, whereas the crrespnding figures fr their nn-mtrised cuntjiparts were 34.2 and 14.1% respectively. The year-wise percentage cntributin f tunas in the ttal tuna catch by different gears is shwn in Fig. 5. The change ver frm nn-mtrised t mtrised traditinal crafts fr tuna fishing was evident frm 1984 nwards. The gears perated frm mtrised crafts which landed nly abut 28 % f the tuna catch in 1983, caught abut 94% f the tuna catch in Fr the veiall perid 1983-'87, hks and lines peratad by mtrised crafts cntributjd the bulk f the catch (46.8%) fllwed by drift net perated frm mtrised ciafts (33.1 %). The cntributins f hks and lines and drift ntts perated frm nn-mtrised crafts were.6 and 9.5 % respectively fr the perid. The average mnthly catch, effrt and catch per unit effrt f lunas in different gears fr the perid 1983-'87 is shwn in Fig. 6. (a) Drift net: The gear was perated in all the years frm mtrised as well as nn-mtrised crafts.

4 B tunas. May was the best mnth f tuna catch by drift net perated frm nn-mtrised crafts. HOOKS AND LINE (M) I DRIFT NET!NM) DRIFT NET (M) E^ HOOKS AND LINE (NM) Eventhugh drift net peratin frm mtrised crafts was bserved in all the years, it intensified cnspicuusly frm 1985 nwards. The annual effrt ranged frm 2,59 units in 1983 t 27,58 units in 1987 with the average annual at 15,97 units. The decline in the effrt f drift net frm nn-mtrised crafts cincided with the increase in the effrt f the same gear frm mtrised crafts. The annual tuna catch ranged frm 2.8 t in 1983 t t in 1987, with the annual average at t. The catch per unit effrt ranged frm 22.1 kg in 1986 t 4.2 kg in 1984, with the annual average at 29. kg. It culd be seen that the catch per trip f tunas frm drift nets perated frm mtrised crafts was almst duble f that perated frm nn-mtrised crafts. Mtrised crafts perated drift nets during all the mnths and the peak effrts were expended during May and September-Octber. The maximum tuna catch was btained during May-June and September- Octber. Prir t drift nets were nt perated during the p;ak suthwest mnsn mnths viz. July- August. It is interesting t nte that the peratin f drift nsts during these mnths in 1987, yielded cmparatively gd catch and catch rates f tunas. Fig. 5. Percentage cntributin f tunas by different gears in the ttal tuna catch. '(M)' indicates gear perated frm mtrised craft and '(NM)' indicates gear pierated frm nn-mtrised craft. (A) 1983, (B) 1984, (C) (D) 1986, (E) 1987 and (F) Average fr the perid 1983-'87. The annual effrt frm nn-mtrised crafts ranged frm 2,97 in 1987 t 14,36 in 1983, with the average at 8,62 units. A reductin in the effrt was seen frm 1984 nwards. Maximum catch (196.21) was nted in 1983 and the minimum (37.81) in 1987, with the annual average at t. Eventhugh the effrt expanded and the tuna catch brught by drift net perated frm nn-mtrised crafts shwed steep decline thrugh l983-'87, the catch per unit effrt did nt shw the crrespnding decline. It ranged frm 14. kg (1983 and '84) t 2.3 kg (1985) with the average at 15.5 kg. The gear was perated in all the mnths except July- August and it was intense during April-May and Octber - Nvember. April - June and September- Nvember yielded cmparatively gd catch rate f (b) Hks and line: The annual effrt f hks and line psrated frm nn-mtrised crafts declined frm 1,37,439 units in 1984 t 8,54 units in 1987 with the average annual at 54,12 units. Tuna catch als declined frm 21.4 t in 1984 t 59.8 t in 1987 with an annual average catch f t. The catch per trip ranged frm 1.5 kg in 1984 t 13.4 kg in 1986 and averaged t 2.8 kg fr the verall perid. A significant aspect nted here was the increase in catch rate with the decrease in fishing effrt frm 1984 nwards. Hks and line fishing frm mtrised crafts intensified fim The annual effrt ranged frm 5,124 units in 1983 t 39,873 units in 1987 with an annual average effrt f 24,437 units. Here als, the increase in the effrt f mtrised units frm 1985 nwards cincided with the decrease in the effrt f nn-mtrised units. The annual tuna catch varied between 31.3 t in 1983 t 1,13.It in 1986 and averaged t t. The catch per trip ranged frm 6.1 kg in 1983 t 33.8 kg in 1986 with the annual average at 26.8 kg. It is seen that the catch per trip f tunas increased with the increase in effrt till 1986, but shwed a slight decline in A cnspicuus increase in the catch per trip f tunas was seen in the mtrised units when cmpared t that frm nn-mtrised units. Maximum effrt f this

5 12 ^8 in ie t 4 1 < 2 J F M A M J J A S O N D \ - 4_ 2^ UJ CO 2 Q z '-< ^^ 1 P^ <^ ) UJ X I < 2-2 ^ Fig. 6. J F M A M J J A S O N D V F M A M J J A S O N D TO^tg Gear-wise average catch (tnnes), effrt and catch per effrt (C/E) in kg f tunas during 1983-'87 ('') at the baseline indicates nn-peratin f the gear), (a) Drift net (nn-mtrised craft), (b) Drift net (mtrised craft), (c) Hks and line (nn-mtrised craft), (d) Hks and line (mtrised craft). UJI3 X unit was expended during July-December. Maximum tuna catch and catch rates were nted during May and Octber-Nvember. Species cmpsitin Seven species f tunas ccurred in the fishery. The verall relative abundance by weight f the species is

6 given in Fig. 7. The bullet tuna Auxis rchei cntributed the bulk f the catch (45.3%) fllwed by the little tunny Euthynnus affinis (34.5%). The ther was the abundance f A. rchei in hks and lines perated frm mtrised crafts, where it fimed abut 74 % f its ttal catch. '."^.v. : : : E-AFFINIS \ -^^ A.ROCHEI gi iisorientalls ^ ffla.thazard f ^ T-TONGGOL.^T-ALBACARES m K-PELAMIS Fig. 7, Species cmpsitin f tunas (all gears tgether) during 19S3-'87. species in the rder f abundarce were Auxis thazard (.2%), Sarda rientalis (5.5%), Thmnus tnggl (2.5%), T. alhacares (1.5%) and Katsuwnus pelamui (.5%). Gear-wise abundance f species The gear-wise species cmpsitin f tunas during the perid is shwn in Fig. 8. In drift net perated frm mtrised and nn-mtrised crafts, E. affinis dminated the catch, fllwed by A. thazard, whereas in hks and line perated frm mtrised and nnmtrised crafts, A. rchei was the dminant species fllwed by E. affinis. A significant aspect nted here In drift net (nn-mtrised craft) E. affinis was abundant during May and Octbei, A. thazard and A. rchei during April and 5'. rientalis during September- Octber. In the same gear perated frm mtrised crafts als E. affinis was abundant during May and Octber, A. thazard in February-April, A. rchei in September and Nvember and S. rientalis in September. In hks and lines psrated frm nn-mtrised crafts, E. affinis was caught abundantly in April and A. rchei during April-May. In the same gear perated frm mtrised crafts, E. affinis was caught in gd quantities during March, May and Nvember, A. thazard during March and A. rchei during May and July t December. Seasnal abundance f species The seasnal trend f different species is shwn in Fig. 9. Tw fishing seasns were nted fr E. affinis viz. April-June and September-Nvember with peak landings during May and Octber. The fishing seasn fr A. thazard was February-April with peak catch in May. May and July t December were the best mnths fr A. rchei with peak catch in Octber. S. rientalis was caught in gd quantities during May t Octber with psak catch in September. The mnthfi f maximum availability f T. alhacares were January and Octber, thse fr T. tnggl June, Octber and Nvember and thse fr K. pelamis January and Octber. Impact f mtrisatin f traditinal crafts Fig. 8. Gear-wise species cmpsitin f tunas during 1983-'87. (A) Drift net (nn-mtrised craft), (B) Drift net (mtrised craft), (C) Hks and line (nn-mtrised craft) and (D) Hks and line (mtrised craft). The mtrisatin prgramme which started gaining mmentum frm 1983, has clearly resulted in an increase in the catch and catch rate f tunas at Vizhinjam. The percentage cntributin f tunas by different gears frm 1983-'87 (Fig. 4) indicates that mtrised crafts have largely replaced the nn-mtrised nes fr hks and line and drift net fishing. The increase in tuna catch frm 1984 nwards (Fig. 2) was chiefly due t the better catch and catch rate f the mtrised units. The catch rate f tunas by drift nets perated frm mtrised crafts was 29. kg as against the same f 15.5 kg frm nn-mtrised units. Similarly hks and lines perated frm mtrised crafts recrded a high catch rate f 26.8 kg in cntrast t 2.8 kg f nnmtrised crafts. The accessibility t new fishing grunds beynd the traditinal areas seems t be the main reasn fr the higher catch rates f mtrised crafts. Anther significant aspect f mtrisatin was

7 I I O Q O n n 2 15 H num nm H LiJ ill < n n nil n n Jl. XLH Hnnn n LL) UJ 2- - cc O - 5- CK - D JO- n UJ A nn JZLXI Q F M A i ^ J J A S O N O LxJ 25 - B CL2-5 n ^llnnn F M A M J J A S O N D Fig. 9. Seasnal trend f tunas during 1983-'87 ('') at the baseline indicates nil catch. (A) E. affinis, (B) A. thazard, (C) A. rchei, (D) S. rientalis, (E) T. albaeares, (F) T. tnggl, (G) K. pelamis and (H) Ttal tuna catch. the change in the pattern f spjcies abundance f the tuna catch in the area. Newfishinggrund fr A. rchei was explited mainly after the intrductin f mtrisatin. Cnsequently, A. rchei became the mst abundantly explited species instead f E. affinis which dminated the fishery prir t mtrisatin f crafts.

8 Cnclusins and recmmendatins (1) A cnspicuus increase in the catch and catch rate f tunas was nted frm 1984 nwards. The average annual catch f tunas during the perid f study was 1,41 t which accunted fr 17.2% f the ttal fish catch in the area. (2) The peak fishing mnths fr tuna were May and September-Nvember. (3) The mtrisatin f traditinal crafts has resulted in an increase in the catch and catch rate f tunas in the area. Mtrised units brught higher prprtin f tuna in their catch. In the ttal tuna catch, hks and line frm mtrised units brught 46.8% and drift nets frm mtrised units 33.1 %. The catch rates in hks and line and drift net were 26.8 kg and 29. kg as cmpared t 2.8 kg and 15.5 kg respectively f the nn-mtrised crafts. (4) The peratin f drift net during the peak suthwest mnsn mnths viz. July-August which was dne nly during 1987, yielded cmparatively gd catch and catch rate f tuna. (5) Auxis rchei was the mst abundant species (45.3%) fllwed by E. affinis (34.5%), A. thazard (.2%) and S. rientalis (5.5%). In drift net E. affinis dminated the catch, whereas in hks and line A. rchei was the majr species. (6) The peak mnths f availability f E. affinis were May and Octber. The best available mnth f A. thazard was May, that f A. rchei was Octbei and that f S. rientalis was September. (7) New fishing grund fr A. rchei was lcated after the intrductin f mtrisatin. (8) Judging by the catch and catch rate f tunas thrughut the year as well as the increased yield f tunas by the explitatin f slightly distant fishing grunds by mtrised traditinal crafts, it is felt that tuna fishing flfers further scpe fr develpment in the area. (9) The chief requirement f tuna fishery develpment in India shuld be the develpment f smallscale fishery sectr. In this cntext, the mtrisatin f small-scale sectr at Vizhinjam, which cnspicuusly augmented the prductin f tunas is a trend wrth encuraging by fisheries develpment agencies. () Diversificatin f drift gill net fishery by the intrductin f pabl type bats deserve urgent attentin. A study f drift gill net fishing with pabl bats at Cchin revealed that in additin t tunas, quality by-catch f ther pelagics such as seer fishes, sharks, carangids, pmfrets and cat fishes which fetch gd price were caught by this fishing. The annual prfit f drift gill net fishing was estimated t be Rs. 28,43. (11) Intrductin f bats fr surface trlling and hks and line fishing beynd 7m depth is anther ptin fr enhancing tuna prductin, especially f E. affinis, A. thazard, A. rchei and T. tnggl in the area. (12) Small purse seiners (OAL m) land gd quantity f tunas frm shelf waters. A regulated purse seine fishery fr tuna alng the suthwest cast f India shuld yield gd results. It is felt that when the harbur facilities at Vizhinjam axe cmpleted, intrductin f small purse seiners may als prve ecnmical.