86 SI 184–192 Journal of Coastal Research Coconut Creek, Florida 2019 ____________________ DOI: 10.2112/ SI86-028.1 received 6 March 2019; accepted in revision 14 May 2019. *Corresponding author: zachariapu@yahoo.com © Coastal Education and Research Foundation, Inc. 2019 Effect of Climatic Variability on the Fishery of Indian Oil Sardine Along Kerala Coast Valiyakath Hussain Sajna † , Pariappanal Ulahannan Zacharia † *, Vazhamattom Benjamin Liya † , Girindran Rojith † , Kuriakose Somy † , Dhanya Joseph † , and George Grinson † ABSTRACT Sajna, V.H.; Zacharia P.U.; Liya, V.B.; Rojith, G.; Somy, K.; Joseph, D., and Grinson, G., 2019. Effect of climatic variability on the fishery of Indian Oil sardine along Kerala coast. In: Jithendran, K.P.; Saraswathy, R.; Balasubramanian, C.P.; Kumaraguru Vasagam, K.P.; Jayasankar, V.; Raghavan, R.; Alavandi, S.V., and Vijayan, K.K. (eds.), BRAQCON 2019: World Brackishwater Aquaculture Conference. Journal of Coastal Research, Special Issue No. 86, pp. 184–192. Coconut Creek (Florida), ISSN 0749-0208. Indian oil sardine (IOS), the commercially and ecologically important pelagic fish of the Kerala coast is susceptible to climatic variation. The study analyzes the impact of climate change on the catch of Sardinella longiceps along the Kerala coast and tries to predict the catch trend under the two RCP scenarios 4.5 and 6.0 for the period 2020-2100. Monthly catch of IOS by major gears for the period 1990-2016 was collected and Relative effort (Effort) and Weighted CPUE (cpue) were accordingly estimated. The climatic variables Sea Surface Temperature (SST), Precipitation (Pr), Chlorophyll a (SSC) and Salinity (SSS) were obtained from NOAA/NASA. The relationship of cpue and Effort of IOS to environmental variables were explored by Generalized Additive Model. The best fit model was selected using lowest Akaike information criterion (AIC) value, Deviance and F statistic. Predictions of cpue and Effort under RCP 4.5 and RCP 6.0 were done and the catch of IOS was estimated. The GAM model revealed the variations in the catch of IOS in relation to climate change. The SST, SSS and Pr showed a negative relation whereas SSC was found to be positively related to the catch of IOS. The results of the study indicate a decreasing trend of cpue and catch and an increasing trend of Effort towards 2100 under both climate change scenarios. ADDITIONAL INDEX WORDS: Climate change, CPUE, generalized additive model, Indian oil sardine, Kerala coast, RCP. INTRODUCTION The climate of our planet is changing and the effects can be seen as global temperature rising, weather getting more extreme, sea levels rising, the oceans becoming more acidic and nutrient loads changing (Brierley and Kingsford, 2009). Increasing frequency and intensity of extreme climate events are likely to have a major impact on the marine environment and indirectly on fisheries (Brander, 2007). Fish species with rapid turnover of generations may show the most demographic responses to these changes (Perry et al., 2005). Fishing shows different trends in response to changes that affect larval stages, reproduction, feeding and migration, as well as anthropic pressures. Possible environmental changes, such as the increased SST, precipitation, chlorophyll concentration and salinity, surge intensity and nutrient concentration mechanisms and can affect the food chain and therefore the abundance, distribution and availability of fish populations (Miller and Schneider, 2000). Tropical species are considered to be especially sensitive to climate change because they live close to their thermal maximum and exhibit limited capacity for acclimation (Stillman, 2003) India is the second largest producer of fish in the world, contributing about 5.43 percent of the world production. The Indian marine fisheries sector thus plays a strategic role in food security, international trade and employment generation in the country (Shyam, Rahman, and Antony, 2015). Among the commercially important marine fish species harvested in India, IOS occupies the foremost position along with mackerel in terms of landings and consumption. Kerala contributes a great magnitude (up to 65%) to the total IOS catch of the country (Shyam, Rahman, and Antony, 2015). Purse seiners, ring seiners (major catch) and the trawlers (by catch) constitute major fishing gears in the region, and are operated actively in locations where the oil sardine schools aggregate. Sardinella longiceps or Indian oil sardine (IOS) is one of the key forage organism for marine predators, including fish, squid, marine mammals, and seabirds. They are of increasing interest for conservation because of their perceived role as critical forage for charismatic mega fauna (e.g., marine mammals and seabirds) in many regions, and are often in the public eye (Cury et al., 2011). The spawning period, (Antony Raja, 1969) feeding habits (Remya and Vivekanandan, 2013) and fishery of IOS is directly and indirectly subjective to changes in climate (Krishnakumar and Bhat, 2008; Kumar et al., 2009). Since the variations in pelagic resources particularly sardine and anchovies are closely linked to the environmental changes on different time and spatial scales, realistic models of these fish populations with climate change and fishing at appropriate scale and resolution are achievable. The interactions between fish and their environment † ICAR-Central Marine Fisheries Research Institute, Kochi, Kerala, India www.JCRonline.org www.cerf-jcr.org