Gillnet colour affects catch efficiency in pearlspot (Etroplus suratensis) tropical estuary fishery

Gillnets are one of the most commonly used fishing gears in both marine and inland waters. Different colour filament nettings are often used in gillnets. However, the effect of gillnet colour on catch efficiency is unclear for most fisheries. Therefore, in this study we investigated the effect of gillnet colour on the catch efficiency in pearlspot (Etroplus suratensis) fishery in Vembanad lake, India. Gillnet colours tested were transparent, green and blue. Results showed that in this fishery, the catch efficiency of gillnets of the three colours tested differed significantly. The highest catch efficiency of pearlspot was shown by green gillnets compared to transparent or blue netting. Specifically, green gillnets on average were estimated to be 74% more efficient compared to transparent gillnets. For the green compared to the blue gillnets, the catch efficiency was estimated to be higher by 81%. These results demonstrate that gillnet colour can be an important factor significantly affecting the catch efficiency of this fishing gear

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Not AvailableBycatch, which includes non-target organisms that are caught during the capture process, is a major problem faced by fisheries, world over. Among the different strategies to reduce the incidence of bycatch, modifications made to the gear to reduce juveniles are very significant. The total bycatch in Indian fisheries was estimated at 58,000 tonnes, which formed about 2% of the total landings. Trawling, though contributes significantly to the marine production of India, about 56% of the total catch of trawlers is bycatch. This bycatch often comprises of juveniles of commercially important species targeted by trawls and other gears. A large number of bycatch reduction devices were designed and field tested in the Indian scenario, among which the square mesh codends were found to be very effective. ICAR-CIFT has successfully demonstrated the utility of square mesh codends in Gujarat, Maharashtra and Kerala and use of these codends are now mandatory in these states. Though selection parameters for different codends (shape, size etc.) are available, a meta-analysis on these results is lacking in India. Trawls, target many resources with varying lengths of capture and hence an optimal mesh size to be used will be a tradeoff between different factors like the length at first sexual maturity, the economic value of the targeted species group and the size and shape consideration of the codend itself. Deriving the best mesh size for the codends hence becomes complicated. This study attempts to optimize the codend mesh size/shape for trawl resources along the Indian coast. Results from 64 selectivity studies on codends carried out along the Indian waters were used. The different species for which selection parameters were available were grouped based on their shape, length-girth relation and the average economic value for the respective species was also considered. The comparative evaluation of L50 values showed that use of square mesh codends increased the L50 by 2-28%. Most of the fishes studied, belonged to the ‘slender’ category, for which square meshes are very effective. The only data available in the ‘flat’ category was for Cynoglossus sp. The study shows that rather than a single mesh size; codend mesh sizes should vary depending on seasons to sustainably and effectively capture trawl resources along the Indian coast. The method and the results of the study and its implications are discussed in the paper.Not Availabl

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Not AvailableCephalopods are mostly targeted by trawlers and Sepiella inermis (spineless cuttlefish), contributes about 2 - 4 percent of total cephalopod landings in India. Cephalopods accounted for 6.9 percent of total landings in Gujarat in 2018, with S. inermis accounting for approximately 1 %. The most common length of this species in the fishery is between 35 mm to 147 mm. The length at first sexual maturity varies along the coast, and recent estimates for west coast of India for this species is 48 and 55 mm for males and females, respectively. There are no estimates of trawl codend selectivity for this species and experiments were carried out using a 40 mm diamond mesh codend using covered codend method. The selection parameters for S. inermis were derived using SELECT methodology and the length at 50 % retention (L50) plus or minus(s.e.) was worked out as 36.2 plus or minus 1.2 mm and selection range as 19.9 plus or minus 2.1 mm. The selection factor and the selection ratio for the codend were worked out as 0.9 and 0.55, respectively. The suggested mesh size for the codend based on length at first sexual maturity (LFM) of females (55 mm) and males (48 mm) were estimated as 60 and 53 mm (diamond mesh), respectively. This is the first estimate of trawl selection for this species and operational parameters like towing speed, codend catch etc., that could influence selectivity were not considered and hence more studies by incorporating these factors will help in further refining the parameters of the selection curve.Not Availabl

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Not AvailableThough trawling contributes significantly to landings in India, issues like bycatch which comprises of juveniles of commercially important species and impacts to the sea bottom are often implicated. There has been a significant increase in the capacity, both in terms of number and in terms of the size of trawlers during the last decade in India. Technical measures like closed season and gear modification are proposed in the Marine Fisheries Regulation Acts of different states. A large number of Bycatch Reduction Devices (BRDs) have been field tested along the Indian waters which have proven to be effective for exclusion of juveniles. Among the different BRDs, square mesh codends are the most popular, due to its conceptual simplicity and ease of modifications of the existing codends. A large number of studies related to the selection parameters for trawlnets of different mesh sizes, are reported from India. This study attempts to review the results of these studies with respect to methods used for deriving the selection parameters. It is observed that variation exists in the methodology adopted for deriving selection parameters among the reports. None of the studies have analyzed the operational factors that affect selectivity of the gear and similarly the survival of the escapees from the BRDs is not quantified. Though preliminary in nature, the selectivity estimates available now are good enough for coming out with proposals regarding the optimum mesh required for individual species. Inclusion of factors affecting selection into the studies, biological parameters of the targeted species and modeling approaches will help in refining the results already available and a development and adoption of a standard protocol for trawl selectivity studies will help significantlyNot Availabl

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Not AvailableThe states of Maharashtra and Gujarat together contribute about 24 per cent of the total catches from Indian waters. Unlike the South-West coast where sardines and mackerel, are the major species, the fishery in this region is dominated by fishes higher in the tropic pyramid. More than 80% of the species in the region have Acetes as predominant food in the guts, which shows the ecological significance of Acetes sp. as a link in the ecosystem. The study was taken up to determine the factors that contributed to the abundance of Acetes along the region, which will be an input for satellite based predictions of fishery resources. Fishing experiments were carried out along Veraval and Diu coasts of Gujarat which have targeted fishery for Acetes using Dept. fishing vessel. Physico-chemical parameters were collected simultaneously from the fishing grounds. The catches of Acetes were highest during post-monsoon and the immediate pre-monsoon. A good correlation (r=0.92) was observed between the Acetes catches and the total CPUE of the catches in trawl catches. The abundance of acetes correlated positively with chlorophyll content in water, which could be taken as a proxy for the plankton abundance. To find the optimum range and predict abundance, analysis based on Random Forest classifiers were used. Chlorophyll and temperature were the most important factors that determined the abundance of Acetes. But the major classification was based on the season and the winter season forming another node. The first node could be further divided based on the chlorophyll concentration which was further separated based on the limiting temperature. In the winter season, the abundance is seen to be based on a lower surface temperature at 25.15 degree celsius. A temperature of 27.25 degree celsius limits the production of Acetes sp. and also the factor seasons, which could be the combined effect of circulations. A species distribution model using maximum entropy data was developed, which proved the reason for distribution of Acetes along the northwest coast and also the discontinuous distribution of Acetes reported in literature. The possibility of inclusion of the results of this study, in the potential fishing, for northwest coast using the concentration of chlorophyll, temperature, phosphate and nitrate is discussed in the paper.Not Availabl

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Not AvailableClimate change is predicted to have direct and indirect impacts on capture and culture fisheries, for fishers, coastal communities and fisheries-dependent economies. Capture fisheries by fishing vessels, is mostly driven by fossil fuels that contribute to greenhouse gas emissions and forms one the largest contributor from the fisheries sector. Transportation of catches, from the landing centers using different modes of transport is another source of emissions which contribute significantly to the emissions. Fisheries may be impacted in different ways, which include changes in the distribution of species due to latitudinal shifts or changes in the productivity of the system through processes that are repercussions due to climate-induced changes. A diverse range of direct and indirect climate affects, including displacement and migration of coastal communities; impacts on infrastructure for fishing; and changes in the frequency, intensity and distribution of extreme events are predicted. The poorer and less empowered countries and individuals are more vulnerable to climate impacts, and the vulnerability of fisheries is likely to be higher in circumstances of overcapacity and over exploitation. The interactions related to climate change is often complex, which includes interactions between social, ecological and economic systems, and this makes future predictions very difficult, however steps are required to develop models that could help the policy makers to frame adaptation strategies. Fisheries governance should aim towards equitable and sustainable options and should be flexible enough to account for inherent uncertainties in the fisheries sector. However, adaptation may be costly, so mitigation of emissions and other factors that contribute significantly to climate related issues should be the main recourse.Not Availabl