Fluctuations in the mackerel catches at Cochin

Abstract

The heavy catches of mackerel were observed during 21st and 28th September. 1982 ,at the Fisheries Harbour, Cochin,by purse-seiners, and since these are quite unprecedented in the recent past, observations made on the biology of the fish and its fishery are presented. The overall size-range of the fish during the month was 153-276 mm and the modal sizes varied between 180 and 250 mm suggesting that the fishery was supported mainly by 1-year and 2-years-old individuals. A majority of fish (58%) were in spent condition followed by immature, spent-recovering and developing individuals. The 92% of the bumper catch of 21st September comprised of spent fish followed by spent-recovering individuals of 2-years-old. Size ranges and dominant modal sizes of mackerel in the purse seine catches during September were compared. The high catch rates, on some these days in September indicates that the mackerel shoals available in the inshore waters were not adequately exploited before the introduction of purse seiners in the area.The comparison of results of the monthly mackerel landings and temperature and salinity values at different centres by various authors reveals that certain optimal levels of temperature and salinity is suitable for the mackerel fishery.