Fishery of full beaks and half beaks with special reference on the growth, mortality and stock assessment of Ablennes hians (Valenciennes) along the 1'uticorin coast, Gulf of Mannar

Abstract

Belonids and hemiramphids commonly known as full and half beaks support a good fishery in Tamil Nadu and on an average 42.6% of this resource in India is landed in Tamil Nadu. They are exclusively exploited by a particular type of drift gillnet. The craft, gear and fish. ng method are dealt with and the catch statistics along with species composition and their abundance are also dealt with in detail. Four species of full beaks namely, Ablennes hians, Tylosurus crocodilus crocodilus, Strongilurus leiura and S. appendiculatus and two species of half beaks namely Hemirhamphus far and H. georgii have been observed to support the fishery. The growth phrameters of A. hians are L = 1,233 mm, K = 0.6052 and t = -0.1178 yr. Based on the length-weight relationship the W_ is estimated to be 3,768 g. The age at first capture th is 0.9825 yr and the age at recruitment is 0.6183 yr. The total mortality rate is estimated to be 3.87, 3.23 and 3.40 during 1990-'91, '91-'92 & '92-'93 respectively and the natunl mortality rate is estimated to be 0.81. The fishing mortality rate for the above period is estimated as 3.065, 2.43 and 2.51 respectively. The exploitation rates estimated for I.he same period are 0.78, 0.72 and 0.74 which indicate that this species is exposed to :l moderately higher fishing pressure by the drift giJInet. Based on the (ohort analysis average annual stock of Ahians is estimated to be 236.5t and the average standing stock is estimated to be 12.4 t along the Tuticorin coast. For Tamil Nadu the average annual stock of Ahians is estimated to be 3,469 t and the average stand: ng stock is 182 t. For a judicious exploitation of this species either a reduction in the effort or an increase in the mesh size of the gear is suggested. Reduction in the effort may not be feasible. Since the aim of the gear is to exploit the full and half beaks the mesh size may be increased.