1Vizhinjam Regional Centre of ICAR- Central Marine Fisheries Research Institute, Vizhinjam, Thiruvananthapuram-695 521, Kerala, India.
2Department of Aquatic Biology and Fisheries, University of Kerala, Kariavattom, Thiruvananthapuram-695 581, Kerala, India.
3ICAR- Central Marine Fisheries Research Institute, Kochi-682 018, Kerala, India.
*Corresponding Author: B. Santhosh, Vizhinjam Regional Centre of ICAR- Central Marine Fisheries Research Institute, Vizhinjam, Thiruvananthapuram-695 521, Kerala, India. Email: santhoshars@gmail.com
The study investigated the length-weight relationship (LWR), relative condition factor (Kn) and sexual dimorphism in Pristipomoides filamentosus, a deep-water snapper of economic importance in the tropical Indo-Pacific region.
A total of 891 fish (476 females and 415 males) were collected from the Vizhinjam fish landing centre at the southern tip of Kerala, India and analyzed from October 2022 to March 2023. The cube law and student’s t-test were applied to calculate LWR and used to check if there was any significant deviation from the cubic relationship of both female and male P. filamentosus. Month- wise and length class-wise, mean Kn was calculated to check the health conditions of both female and male P. filamentosus. Body colouration, fin pigmentation and external characteristics of genital papillae and urogenital regions are used to explore the sexual dimorphic characteristics of P. filamentosus.
Growth was negatively allometric and the coefficient of determination (R2) for female, male and pooled sexes were 0.966, 0.976 and 0.970, respectively. The relative condition factor (Kn) was highest for females (1.20±0.02) in November and for males (1.17±0.02) in October. Additionally, fish with fork lengths (FL) between 49.5-54.5 cm exhibited the highest Kn values for females (1.31±0.04), while those with FL ranging from 54.5-59.5 cm showed peak Kn values for males (1.21±0.05). The average Kn value for P. filamentosus was approximately one, indicating that the fish were generally in good condition. Sexual dimorphism is more evident in mature P. filamentosus shows characteristic changes in females and males, including body and fin colouration (dichromatism) and external characteristics of the urogenital region and genital papillae. This study provides baseline information and reference points for effectively managing and conserving P. filamentosus.
Allometric growth, Genital papillae, Lutjanidae, Sexual dichromatism, Urogenital region
