Development of pelagic longline gear for the exploitation of Needle fishes along the coast of Ramanathapuram district, Tamil Nadu
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Date
2016
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Fisheries college and Research Institute, Thoothukudi, Tamil Nadu Fisheries University
Abstract
The present study dealt with evolving a selective long line gear alternate to pelagic drift gillnets to capture Needlefishes. A survey undertaken in Ramanathapuram district on the drift gillnet fishery revealed many common
features in the net designs. Six species of Needle fishes such as Ablennes hians, Tylosurus crocodiles, T. choram, T. agus, Strongylura strongylura and S. leiura were found to constitute fishery in the gillnets with the domination either by
A. hians or by T. crocodiles. The point of the ‘J’ hook bearing hook No.10 was bent manually to right by 5° to make ‘Reversed hook’ and the same was bent to left by 5° to make ‘Kirbed’ hook. Four units of experimental longlines
each with 350 hooks of different design such as (i) ‘J’ hook (ii) Reversed hook (iii) Kribed hook and (iv) Bait holder hook were designed and fabricated. Fishing trials were conducted from March 2016 to June 2016 in the coastal waters of Mundal fishing village of Ramanathapuram district.
Four species of Needle fishes viz. A. hians, T. crocodiles, T. choram and S. strongylura were found to form fishery in the experimental longlines. Domination of T. crocodilus followed by A. hians invariably in the catches of all
the four experimental long lines revealed the fact that T. crocodilus is more vulnerable than to A. hians longlines. Significant difference could be observed between the catch rates of different species (P<0.0) besides catch rates of
different hooks studied (P<0.05). Among the gears tested, the long line unit with ‘Reverse hooks’ showed highest overall hooking rate of 7.4 % indicating more vulnerability of Needle fishes to hooks with its point bent towards right (i.e.
Reversed hook). Though sporadic occurrences of sucker fish (Echenis naucrates) and the cat fish (Arius thalassinus) could be observed during experimental fishing trials, the bycatch was insignificant compared to that of gill nets.
Among the fishes caught T. crocodiles showed 4 % increase in fish catch when the catch was expressed in terms weight particularly in gears with ‘J’ and ‘Reversed’ hook due its higher weight in relation to length compared to other species. Despite its low hooking rate, Kribed hook ranked first in terms of hooking ability at correct position (i.e at Jaw) (51%). The ‘J’ hook was found to have highest percentage of hooking at throat (33%) and gut (21%) which are not proper hooking locations as for as longlining is concerned. The ‘Bait holder’ hook followed by ‘Reversed hook’ was found to be more efficient in bait holding efficiency. Sardinella fimbriata could serve as in ideal bait for capture of Needle fishes by long lines owing to its low cost and easy availability. The study revealed that operation of newly evolved longline gear with 2,800 ‘Reverse hooks’ would to be a better alternative to pelagic drift gillnets of Ramanathapuram district for the capture of Needle fishes owing to higher selectivity for Needle fishes and lesser cost of construction and operation.
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