No abstract

Fishery of the Indian mackerel Rastrelliger kanagurta (Cuvier, 1816) from Tuticorin was studied for the period 2011-2014. Indian mackerel formed fishery round the year in Tuticorin with peak during June to November in trawl and October to December in gillnet. The annual catch varied from 1650 to 5101 t (average 2968 t) in gillnet and from 815 to 1716 t (average 1231 t) in trawl. Total length (TL) of the fishes ranged from 10 to 30.5 cm. Length-weight relationship estimated was W = 0.0038777 * L 3.3 (r 2 = 0.99, n = 535, L=TL in cm, W in g). The fishes were found to be continuous spawners with peak spawning during January to August and November. The von Bertalanffy growth equation derived was Lt = 31.2 [1-e -1.3(t+t0) ]. The species attained TL of 22.7 cm in 12 months and 28.9 cm by the end of second year. Longevity estimated was 2.3 years, Phi-prime index (ᴓ) was 7.143, while Z and M were 4.36 and 2.132 respectively. Thompson and Bell model showed continuous increase of yield even after considerable rise in F-factor. Spawning stock biomass (SSB) was 79% at an f-factor of 3.5. F 0.1 using Beverton and Holt Y/R model was 3.4 whereas the present F was 2.23 indicating that the current level of fishing is not affecting the stock adversely.

The present study describes the status of multiday drift gillnet fishery for tuna from Chennai fishing harbour based on data for the years 2016 -2017. The data is also compared with that during 1999-2006. Both the craft and gear increased in size with consequent extension of fishing grounds and increase in the number of days/ fishing trip. The size of the boats increased to 20-23 m OAL from 11-12 m OAL and weight of the gear from 1 to more than 6 t. Annual average catch increased to 8523 t during 2016-2017 from 595 t during 1999-2006. Average catch per unit effort was 8310 kg as against 730 kg during 1999-2006. Yellowfin tuna, Thunnus albacares and Skipjack tuna, Katsuwonus pelamis were the dominant species. The stock position of skipjack tuna and yellowfin tuna vis-àvis the three indicators indicated that the percentage of mature yellowfin tuna in the catch in 2017 was 68%, fish in optimum length 35% and mega-spawners 33% whereas in skipjack tuna the respective percentages were 99.5, 21.1 and 79.1. Problems and prospects of multiday tuna drift gillnet fishery are also discussed.