Age and growth of four spot megrim (Lepidorhombus boscii) in northern Iberian waters corroborated by cohort tracking

Age and growth are key biological aspects for the age-structured assessment of exploited fish populations. Confirming the consistency of fish age interpretation by validation/corroboration studies is essential for providing accurate age estimates to the stock assessment process. The Atlantic Iberian stock of four-spot-megrim (Lepidorhombus boscii), an important exploited demersal fish, is annually assessed by age-structured models in ICES, and specimens are routinely aged by IEO expert readers for this purpose. A total of 11,741 otoliths of this stock were aged from 23 annual groundfish surveys carried out in Cantabrian Sea and Galician waters (ICES Div. VIIIc, IXa) and following internationally standardized protocols. Annual age-length-keys were built using the respective age estimates and applied to the length distribution of each survey, thus obtaining a matrix of abundance indices by age and year. Similar mean lengths are obtained for each age group along most of the time-series. The von Bertalanffy growth parameters for the time-series are estimated (L∞: 49.0; k: 0.13; t0: 1.13) and the results are compared with previous studies. The annual growth pattern estimated for L. boscii is here corroborated by tracking cohort abundance indices in the surveys. The current otolith age estimation criterion used and the resulting age estimates obtained by the age readers can be considered valid. Strong and weak cohorts are well tracked along most of their age classes, and the correlations between age abundance indices are statistically significant up to the age 6, which represent around 95% of the total number of this species caught in the surveys. The findings here presented on the age of L. boscii and its corroboration can help to reduce the uncertainty in the estimation of its demographic structure and hence, ultimately, it will be important for a better understanding of its relevance in the functioning of the benthic community of the shelf.Versión del edito

Recovery of two specimens of anglerfish Lophius piscatorius Linnaeus, 1758 in the northern stock (ICES Divisions VIII a and b) after being tagged in the southern stock (Division VIII c)

The present paper provides a first report on the recovery of two specimens of anglerfish Lophius piscatorius Linnaeus, 1758, both of which had been tagged in ICES Division VIII c (southern stock of anglerfish) and where recovered in Divisions VIII a and b (northern stock). The first of these recoveries, tagged on 22 October 1996 in the Cantabrian Sea waters off the coast of Fuenterrabía (Spain), took place on 10 January 1997 off the coast of Biscarrose (France). In the 80 days from tagging to recovery, its length had increased by 3 cm and it had travelled approximately 109 km. The other specimen was tagged on 20 December 1995 in the Cantabrian Sea waters off the coast of Santander (Spain) and recovered at the beginning of March 1997 off the coast of La Rochelle (France). During these 440 days, the fish travelled approximately 292 km.En este trabajo se notifica por primera vez la recuperación de dos ejemplares marcados de rape Lophius piscatorius Linnaeus, 1758. Ambos ejemplares fueron marcados en la división VIII c del CIEM (stock sur de rape) y capturados de nuevo en las divisiones VIII a y b (stock norte). El primer ejemplar fue marcado el día 22 de octubre de 1996 en aguas del mar Cantábrico, frente a la costa de Fuenterrabía (España), y recuperado el 10 de enero de 1997 frente a las costas de Biscarrose (Francia). Su talla aumentó 3 cm y se desplazó aproximadamente109 km desde el lugar de marcado, tras pasar 80 días en libertad. El segundo ejemplar fue marcado el 20 de diciembre de 1995 en aguas del mar Cantábrico, frente a la costa de Santander (España), y recuperado a primeros de marzo de 1997 frente a las costas de La Rochelle (Francia). Se desplazó aproximadamente292 km desde el lugar de marcado, tras pasar aproximadamente 440 días en libertad.Instituto Español de Oceanografí

Black anglerfish (Lophius budegassa): weight-length relationships, weight conversion factors and condition factor trends from a decade of two stocks, in ICES Div. VIIIc-IXa (northern Iberian Atlantic waters) and in Div. VIIb,c,h,j,k (Celtic Sea, south-western Ireland and Porcupine Bank)

Weight-length relationships, weight conversion factors and condition factor are presented from a decade (2006 to 2015) for both stocks of black anglerfish (Lophius budegassa) in northern Iberian Atlantic waters (ICES Div. VIIIc-IXa) and in Celtic Sea, south-western Ireland and Porcupine Bank (ICES Div. VIIb,c,h,j,k). A total of 2035 and 1263 specimens were sampled respectively in each stock from commercial landings and research surveys. Total length [Lt (cm)], total weight [Wt (g)], “commercial” weight (gutted with liver) [Wgl (g)] and “scientific” weight (gutted without liver) [Wg (g)] were obtained. The weight-length relationships for the combined sexes were: Lt = 0.020 Wt2.916; Lt = 0.017 Wgl2.929; Lt = 0.017 Wg2.922 in Div. VIIIc-IXa, and Lt = 0.025 Wt2.841; Lt = 0.013 Wgl2.984; Lt = 0.013 Wg2.971 in Div. VIIb,c,h,j,k. The conversion factors (total weight - gutted weight), useful in fisheries management due to the commercial landings of this species are available in gutted weight, were: Wt = 1.186 Wgl; Wt = 1.236 Wg in Div. VIIIc-IXa, and Wt = 1.187 Wgl; Wt = 1.233 Wg in Div. VIIb,c,h,j,k. These updated values can be used in the process of the annual assessment of the state of both stocks in the ICES working group. The evolution of the condition factor over the year, indicator of nutritional status evolution, is also estimated for immature and mature individuals of each sex, showing some seasonal variation. The results are similar to the previously estimated in other studies