Biology and life history characteristic of selected Deepsea fishes including otolith
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Date
2021
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Fisheries College and Research Institute, Tamil Nadu Dr. J. Jayalalithaa Fisheries University, Thoothukudi
Abstract
The Present work was carried out to understand the biology and life history characteristics of deep-sea fishes around the Indian EEZ. For the present study, fish samples were collected from the exploratory deep-sea bottom trawling operations conducted onboard FORV Sagar Sampada in the cruise 398. Trawling was carried out in the Arabian Sea between Latitude 80 N and Longitude 760 E and in Bay of Bengal between Latitude100 N to 170 N and Longitude, 800 E to 830 E. Biological studies were carried out on four deep-sea fish species collected from the cruise landings. The four species selected was Parascombrops pellucidus (Acropomatidae), Alepocephalus blanfordii (Alepocephalidae), Pterygotrigla hemisticta (Triglidae) and Lamprogrammus niger (Ophidiidae). Length- Weight relationships (LWRs) was estimated in selected species to predict the condition and growth pattern, as well as to calculate the biomass from the length. The b value calculated in the present study for P. pellucidus was 3.34 (t-test, P 0.05) and L. niger 3.33 (t-test, P 0.05) showed negative allometric growth. Food and feeding studies revealed that higher feeding intensity was noticed in P. pellucidus and A. Blanfordii, the major food items of these fishes was deep-sea shrimps, non- penaeids prawns, fishes, and Squids. More empty stomachs were observed noticed in P. hemisticta and in L. niger, this food mostly of digested matter and Shrimp. Prey groups were interpreted by using Index of Relative Impotance. P. pellucidus higher IRI value was noticed for non- penaeid (4316) and fish species Vincigueria nimbaria (1449) and in A. blanfordii shrimp (2274) and sediments (2023) showed higher IRI values. Higher GaSI was recorded for P. pellucidus (4.971), HeSI, and relative condition factor for P. hemisticta (4.282 & 1.108). Sex ratio showed female domination in P. pellucidus and P. hemisticta and Male dominations in A. blanfordii and L. niger. Female of all the four species were in matured condition (> 60 %) and spawning season commence during the in monsoon months except for A. blanfordii where it’s breeding season is during pre-monsoon. The estimated fecundity of P. pellucidus ranges from 1362 – 15880 eggs, A. blanfordii 325 – 1656 eggs, P. hemisticta 21733 - 83757 eggs and in L. niger 87261-175896. Egg diameter was measured and their ranges various (immature to fully mature) in P. pellucidus from 0.158 - 0.834, A. blanfordii 0.993 - 4.727, P. hemisticta 0.221-1.523 and L. niger 0.190- 0.920. LWRs between otolith weight (OWe) and otolith length (OL) and height (OH) showed negative allometric relation OL × OWe (b value range from 2.079-2.759) and OH × OWe (b value range 1.929-3.05) of four species showed negative allometric relation except for the P. hemisticta the relationship OH × OWe was noticed as isometric growth (b value 3.05). Otolith area and otolith length gives better estimations for P. pellucidus, P. hemisticta, and L. niger, and otolith weight was found to be most suited for predicting the size of A. blanfordii. Our studies indicated equations derived using all otolith morphometric variables and fish lenght can give accurate estimations for reconstructing the prey size (r2 ranges from 0.93 to 0.73). The highest r2 value of 0.93 was reported for the relationship between OA and TL (P. pellucidus) and the lowest r2 value of 0.46 was obtained for the relationship between OP and TL (L. niger). The current study enlightens the knowledge on the biology and life history characteristics of four deep-sea fishes, which was for the first time around the Indian region and globally.