Weight–length relationships, weight conversion factors and somatic indices from two stocks of black anglerfish (Lophius budegassa) and white anglerfish (L. piscatorius) in north-eastern Atlantic waters

Abstract

Weight–length relationships, weight conversion factors and somatic indices are presented from a decade (2006 to 2015) for two stocks of Lophius budegassa and L.piscatorius in northern Iberian Atlantic waters (ICES Div. VIIIc–IXa2) and in Celtic Sea, south-western Ireland and Porcupine Bank (Div. VIIb,c,h,j,k). A total of 3298 L.budegassa and 7219 L.piscatorius were sampled from commercial landings and research surveys. Total length (Lt), total weight (Wt), “commercial” weight (Wgl) and “scientific” weight (Wg) were obtained. The parameters (a, b) in the power relationships weight–length for combined sexes in L.budegassa were: 0.020, 2.916; 0.017, 2.929; 0.017, 2.922 for Wt, Wgl and Wg respectively in Div. VIIIc–IXa2; 0.025, 2.841; 0.013, 2.984; 0.013, 2.971 in Div. VIIb,c,h,j,k. For L.piscatorius: 0.025, 2.853; 0.020, 2.868; 0.024, 2.861 in Div. VIIIc–IXa2; 0.027, 2.826; 0.023, 2.825; 0.023, 2.816 in Div. VIIb,c,h,j,k. Significant differences between stocks were found in both species. The conversion factors between total and gutted weight in L.budegassa were: 1.186, 1.236 for Wgl and Wg respectively in Div. VIIIc–IXa2; 1.187, 1.233 in Div. VIIb,c,h,j,k. For L.piscatorius: 1.181, 1.241 in Div. VIIIc–IXa2; 1.210, 1.262 in Div. VIIb,c,h,j,k. The parameters can be used in the process of annual assessment of the state of each stock. Gonadosomatic index (GSI), hepatosomatic index (HSI) and Le Cren’s condition factor, indicators of reproductive and nutritional status, were seasonally analyzed and compared between sexes and stocks. Significant better condition and higher GSI and HSI were found in females. In Div. VIIb,c,h,j,k better condition was found for both species and higher GSI for L.piscatorius. The analysis throughout the year of GSI and HSI for L.budegassa showed seasonality in liver growth previous to spawn and corroborated the spawning season from January to June in VIIIc–IXa2. The parameters obtained were compared with previous ones from these and others Lophiiformes, showing common patterns.