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Introduction

In Indian waters, marine catfishes were represented by 23 species, of which 11 species forms commercial fishery.¹⁷The distribution of ariids all along the Indian coast between 30 and 80 m depths with maximum abundance over inshore muddy bottom habitats.^16,19,21In India, the average annual landings of marine catfish was 11,779 tonnes (1950) which are mainly exploited by artisanal sectors.¹⁹Catfish fishery in Maharashtra is supported by 10 species of whichPlicofollis dussumieri, P. tenuispinis, Nemapteryx caelataandOsteogeneiosus militarisforms 93 % of the total catch of the Maharashtra state.^7、8Anintroduction of mechanised trawlers (1966-75) and purse seiners (1976-80) in Maharashtra coast resulted increase in catfish catch, with the maximum landings of 67,666 tonnes was noticed in 1982, thereafter the landing decreased gradually to 45,335 t in 2005 with the recorded minimum landing in 1995 (37, 518 t).^1,10,18,24The possible reasons coule be attributed to low fecundity and exhibition of oral incubation and shoreward breeding migration. Preference in movement of shoals of brooding male to shallow coastal waters is vulnerable to fishing mortality by bottom trawling and by purse seine.^{3,4,5,18,22,27}Mean length at exploitation was found lower than L_mresulted in heavy fishing pressure on juveniles and sub adults of these resources in Mumbai waters.²⁴New Ferry Wharf (NFW) is one of the major fish landing centre in India representing 33 % of the trawl catch of Maharashtra state.^2,6No recent information on juvenile landings of the marine catfishes and its economic loss to the fishers are available along Maharashtra coast. Hence, the present paper aims to quantify the juvenile landings in shrimp trawlers in New Ferry Wharf (NFW) landing centre of Mumbai waters and its economic evaluation due to juvenile fishing.

Table 1: Length at first maturity, L_meanand average annual landing prices of four dominant marine ariids during January to Decemeber 2013

Materials and Methods

The samples were collected during January to December 2013 from multiday trawlers of NFW operated along south of Saurashtra coast to Ratnagiri coast (17⁰-21⁰N and 71⁰-73⁰E) with depth range from 10 - 60 m (Figure 1). The total catch, length frequency data on the landings of juveniles and adults and also their price of all four species were made at NFW landing centre on weekly basis. The catch data was not available from 1^stJune to 15^thAugust due to trawl ban imposed by the Maharashtra government. The total length was measured using digital vernier calliper to the nearest mm. The total number of boats landed and the total catch landings of four species were obtained from the database at Mumbai Research Centre of Central Marine Fisheries Research Institute.

Figure 1: Shows trawl sampling ground withdepth contour during January to Decemeber 2013 Click here to View figure

Figure 2: Percentage distribution of juveniles in various size groups of marine ariids during January to Decemeber 2013 Click here to View figure

Table 2: Economic evaluation of juveniles of four dominant marine ariids during January to Decemeber 2013 Click here to View Table

The catch recorded from the observed number of boats on the day of observation was raised to total number of boats landed on that day, and then raised to the month. The monthly estimates were used to arrive at annual estimates by taking into consideration the number of fishing days and monthly estimated number of boats by following the method of Alagaraja and Srinath (1980).²每个speci的成人和青少年的数量es landed during the study period was estimated based on length at first maturity collected from published papers for each species. The proportion of juveniles and adults from observed length frequency data was determined for all the four species.

Species-wise total juvenile and adult weight corresponding to length data was calculated based on length-weight relationship method.¹⁵Adult biomass corresponding to 1 kg of juveniles was obtained from bioeconomic model and economic loss due to juvenile fishing were estimated following the method of Najmudeenet al(2008).²³The mortality rate was calculated as the proportion of total and natural mortality.¹⁴The economic loss due to juvenile landings of each species was estimated by assuming that the weight gained if they were allowed to grow up to length at first maturity. The concept is that length of most animals in the population would have an opportunity to become mature and spawn and contribute to the future generation sustainably. The annual average landing centre price of juvenile and adult of each species were used to estimate the economic loss.

Results and Discussion

The length range, length at first maturity (L_m), average annual mean length (L_mean) and average annual landing price structure of juveniles and adults during study period of all the four species are shown in Table 1. The percentage distribution of juveniles size ranges of different species landed are as shown in Figure 2.

The estimated annual juvenile landings ofNemapteryx caelataformed 93.17 % of total catch with peak during October to January (Table 2) and minimum size range recorded was 130-139 mm. InN. caelata,L_meanwas 268 mm and L_mwas 408 mm, if juveniles are not caught and allowed to grow up to L_m,an additional revenue of Rs. 9.99 crores (Table 2) would have been realized and biomass added was found to be 1,250 tonnes per annum. It was evident from the present study that notable reduction in L_meanfrom 300 mm in 1990’s to present 268 mm and the reason may be due to growth over fishing of the stock by bottom trawlers in Northwest coast.^5,7The present results showed that annual biomass is increased by 2.96 times with 5.26 times increase in revenue, if juveniles are caught beyond L_m. Diet composition studies by Raje (2006) showed that 56.62 % of theN. caelatadiet is crustacean and during spawning seasons (February to June & July to January) no mature fish was observed which coincide with the juvenile abundance of present study period.^{9, 25}

The estimated annual juvenile landings ofPlicofollisdussumieriformed 57.14 % of total catch with peak landing is from November to January (Table 2) and minimum landed size range was 180-189 mm. InP. dussumieri,L_meanwas 298 mm and L_mwas 351 mm, if juveniles are not caught and allowed to grow up to L_m,an additional revenue of Rs. 3.48 crores (Table 2) would have been realized and biomass added was found to be 434 tonnes per annum. The present results showed that annual biomass is increased by 1.97 times with 3.16 times increase in revenue, if juveniles are caught beyond L_m.

The estimated annual juvenile landings ofOsteogeneiosusmilitarisformed 36.11 % of total catch with peak landing is from January to March (Table 2) and minimum landed size range was 120-129 mm. InO.militarisL_meanwas 291 mm and L_mwas 392 mm, if juveniles are not caught and allowed to grow up to L_m,an additional revenue of Rs. 2.7 crores (Table 2) would have been realized and biomass added was found to be 300 tonnes per annum. The decadal decline in L_meanfrom 300 mm in 1990’s to present 291 mm and L_mean< L_mevidenced due to growth over fishing of the stock was observed during the present study period.^5,7,9The present results showed that annual biomass is increased by 2.96 times with 5.26 times increase in revenue, if juveniles are caught beyond L_m. Studies on index of preponderance showed high value from February to June which coincide with the juvenile abundance of our study period. Diet composition mainly consists of polycheates, penaeid prawns, crabs, molluscs and brittle stars proven to be a voracious bottom feeder and are more vulnerability to bottom trawl fishery.²⁵Moreover, occurrence of juveniles landings ofO. militariesthroughout the year is furthur supported by their fractional spawning behaviour from August to April.^7、8

The estimated annual juvenile landings ofPlicofollistenuispinisformed 21.43 % of total catch with peak landings in January, March, May and October (Table 2) and minimum landed size range was 190-199 mm. InP.tenuispinis,L_meanwas 290 mm and L_mwas 416 mm, if juveniles are not caught and allowed to grow up to L_m,Rs的额外收入。1.25卢比(表2)would have been realized and biomass added was found to be 434 tonnes per annum. The present results showed that annual biomass is increased by 1.68 times with 3.35 times increase in revenue, if juveniles are caught beyond L_m. Diet composition is dominated by squilla, crabs, prawns and bivalves indicates its preference on bottom dwelling organisms.⁷The spawning season from September to November, March and May coincided with juvenile abundance indicating theses species are more vulnerable to bottom trawl.^7,9,13,19

The utilization of low value by catch (LVB) over the period in Indian coast increased from 14% in 2008 to 25% in 2011, this increasing trend was due to increase in price and demand for LVB for the production of fish meal and fertilizer.^{11, 12}In India, the literature reveales that very few researchers had estimated the economic loss of bycatch from trawl net. Najmudeen and Sathiadas (2008)²³estimated the economic loss due to juvenile fishing from trawlers of India was 15,686 million US dollars per annum. Salim (2014)²⁶estimated economic deficit of juvenile landings in trawl net of Ernakulum district, Kerala with loss of Rs.1350 per trip per trawl. Dineshbabu (2013, 2014)^11,12estimated economic loss due to landing of low value finfish as bycatch in trawl net along Mangalore coast, Karnataka during 2011 and the loss was found to be Rs. 280 million and Mohammedet al²⁰found that estimated economic deficit on juvenile landings forUroteuthis(P) duvaucelii,Sepia pharaonisandOctopus membranaceousalong east and west coast of India was about 425 crores. Kameiet al(2013)¹⁴estimated the economic loss of juvenile landings of six dominant species of sciaenids at New Ferry Wharf was at about 68 crores. Recently, Sugumaret al²⁸estimated economic loss of five dominant species of cephalopods in Mumbai waters and the loss was found to be 33.22 crores.

It is evident from this study that juveniles are found abundant during the period between November to March which agrees with the findings by Kameietal (2013)¹⁴and Sugumaret al(2015).²⁸The inshore and coastal waters from southern Saurashtra to Ratnagiri may act as feeding ground for most of the dominant commercial important species during these months. Several authors^16,19,21observed the prevalence of marine catfish ranged between 30 and 80 m depth. coincided with the present study wherein depth range was found to be 10 – 60 m for these species. The operation of trawlers in the traditional fishing area brings alarming situation on these resources so strict ban should be enforced on mechanised trawlers in coastal waters of Maharashtra. Maximum economic again will be realized only through stakeholders participatory approach of management measures, such as effort restriction in combination with strict mesh size regulation for sustainable harvest of these resources.

Acknowledgement

The authors thankful to the Directors of CMFRI, Kochi and CIFE, Mumbai for providing us with all the facilities and logistic support.

References

1. Alagaraja, K. and Srinath, M. Assessment of the resources of important species of catfishes. - Marine catfish resources of India: Exploitation and prospects,CMFRI Bulletin40:70-94 (1989).
2. Alagaraja, K. and Srinath, M. Marine fish landings in India – estimates and precision.Indian Journal of Fisheries, 27 (1&2):155-160 (1980).
3. Amin, M., Shoaib, M., Nabi, G., Ahmed, N. and Kifayatullah, M. A comprehensive review on fishery biology of catfishes.Journal of biology and life science, 7(1):1-11 (2016).
4. Bijukumar, A., and Deepthi, G.R. Trawling and by-catch: Implications on marine ecosystem.Current Science,90:922-931 (2006)
5. Chakraborty, S. K., Deshmukh, V. D., Khan, M. Z., Vidyasagar, K. and Raje, S. G. Estimates of growth, mortality, recruitment pattern and maximum sustainable yield of important fishery resource of Maharashtra coast.Indian Journal of Marine Science, 26: 53 – 56 (1997)
6. CMFRI, FRAD, Marine fish landings in India – 2013.Technical Report. CMFRI, Kochi. 36pp (2014)
7. Annual Report 2012-2013, 47 (2012)
8. Annual Report 2013-2014, 47 (2013)
9. Marine catfish resources of India: exploitation and prospects.BulletinCentral Marine Fisheries Research Institute, 40:1-94 (1987)
10. Dan, S. S. Maturity, spawning and fecundity in the catfish Tachysurus tenuispinis (Day).Indian Journal of Fisheries, 24(1&2):96 – 106 (1977)
11. Dineshbabu, A. P., Radhakrisnnan, E. V., Sujitha Thomas, Maheswarudu, G., Manojkumar, P. P., Kizhakudan, S. J., Pillai, S. L., Chakraborty, R. D., Jose, J., Sarada, P. T., Sawant, P. S., Philipose, K. K., Deshmukh, V. D., Jayasankar, J., Ghosh, S., Koya, M., Purushottama, G. B. and Dash, G. An appraisal of trawl fisheries of India with special reference on the changing trends in bycatch utilization.Journal of Marine Biological Association India, 52:69-78 (2013)
    CrossRef
12. Dineshbabu, A.P., Sujitha Thomas., and Vivekanandan, E. Assessment of low value bycatch and its application for management of trawl fisheries.Journal of Marine Biological Association India, 6(1):103-108 (2014)
13. James, P. S. B. R., Bande, V. N., Menon, N.G. and Balachandran, K. The catfish resources of south-west coast of India prospects and management problem.CMFRI Bulletin, 44:78-94 (1989)
14. Kamei, G., Chakraborty, S. K., Deshmukhe, G., Jaiswar, A. K., Devi, H. M., Kumari, S., and Sreekanth, G. B. Assessment of economic impact of juvenile fishing of sciaenids along Mumbai Coast, India.Indian Journal of Geo-marine Sciences,42(5):617-621 (2013)
15. Le Cren, E. D. The length-weight relationship and seasonal cycle in gonad weights and condition in the Perch (Perca fluviatalis).Journal of Animal Ecology, 20:201-219 (1951)
    CrossRef
16. Menon, N. G. and Bande, V. N. Taxonomic considerations and general distribution of commercially important catfishes.CMFRI Bulletin- Marine catfish resources of India: Exploitation and prospects, 40:5-11 (1987)
17. Menon, N. G. Catfishes. In: Mohan Joseph, M. and Jayaprakash, A. A. (Eds). Status of Exploited Marine Fishery Resources of India. CMFRI, Kochi, 110-119 (2004)
18. Menon, N. G., Balachandran, K., Zacharia, P. U., Raje, S. G. and Feroz Khan, M. Marine catfish resources of India. In: In: Pillai, V. N. and Menon, N.G. (Eds), Marine Fisheries Research and Management. CMFRI; Kochi, 579-603 (2000).
19. Menon, N. G., Srinath, M., Appanasastry, Y., Raje, S. G., Zacharia, P. U. and Feroz Khan, M. Stock assessment of marine catfishes of India.Indian Journal of Fisheries, 39 (1&2):65-84 (1992).
20. Mohamed K. S., Joseph M., Alloycious P. S., Sasikumar G., Laxmilatha P., Asokan P. K., Kripa V., Venkatesan V., Thomas S., Sundaram S., and Rao G. S. Quantitative and qualitative assessment of exploitation of juvenile cephalopods from the Arabian Sea and Bay of Bengal and determination of minimum legal sizes.Journal of Marine Biological Association India, 51(1): 98 – 106 (2009)
21. Mukundan, C. General features of catfish fishery.CMFRI Bulletin- Marine catfish resources of India: Exploitation and prospects, 40:2-5 (1989)
22. Mukundan, C. Some special features of catfish fisheries for consideration in developmental programmes.CMFRI Bulletin- Marine catfish resources of India: Exploitation and prospects, 40:88 (1987)
23. Najmudeen, T. M., and Sathiadhas, R. Economic impact of juvenile fishing in a tropical multi-gear multi-species fishery.Fisheries Research, 92:322-332 (2008)
    CrossRef
24. Raje, S. G. and Vivekanandan, E. Vulnerability of catfish to fishing: an investigation based on the landings at Mumbai.Indian Journal of Fisheries, 55(3):227-233 (2008).
25. Raje, S. G. Some aspects of biology of catfishes Tachysurus caelatus (Valenciennes) and Osteogeneiosus militaris (Linnaeus) from Mumbai.Indian Journal of Fisheries, 53(3): 330-343 (2006)
26. Salim, S. S., Aswathy, N., Vipinkumar, P., and Geetha, R. Economic externalities of low value fishes in trawl operations in Kerala.Indian Journal of Fisheries, 61(2):103-107 (2014)
27. Sastry, Y. A. and Kasim, H. M. The fishery and catch statistics of catfish,CMFRI Bulletin印度海洋鲶鱼资源:剥削and prospects, 40:12-57 (1989)
28. Sugumar R., Sundaram S., Jaiswar, A. K., Lakshmanan, R., Chakraborty, S. K. and Kavungal, V. An Evaluation of Economic Impact on Juvenile Landings of Cephalopods in Mumbai Waters, Northwest Coast of India.当前世界环境,10(3):1004-1010 (2015)
    CrossRef