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

Weight-length relationships, weight conversion factors and condition factor trends for two stocks of black anglerfish (Lophius budegassa) in southern Bay of Biscay, Galician waters and northern Atlantic areas from a decade

The weight-length relationship has a wide application in fish biology and fisheries management, such as for predicting weight from length data, or for the calculation of production and biomass of a fish stock. Weight-length relationship, weight conversion factors and condition factor are presented from a decade (2006 to 2015) for both stocks of black anglerfish (Lophius budegassa) in southern Bay of Biscay and Galician waters (ICES Div. VIIIc-IXa, southern stock) and in Celtic Seas (ICES Div. VIIb,c,h,j,k, northern stock). 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. These updated values can be used in the annual assessment of the state of both stocks in the ICES working group, replacing those previous estimated more than a decade ago. The conversion factor (total weight - gutted weight) here estimated is also useful in fisheries management due to the commercial landings of this species are available in gutted weight. The evolution of the condition factor along the year, indicator of nutritional status evolution, is estimated and can be a proxy for estimating the spawning season. Its evolution is studied throughout the year for immature and mature individuals of each sex. The results are similar to the previously estimated in other studies

Four spot megrim (Lepidorhombus boscii) weight-length and weight-weight relationships in northern Iberian waters (stock 8.c, 9.a)

Total weight-length, gutted weight-length and total weight-gutted weight relationships were fitted for the Iberian Atlantic stock of four spot megrim (Lepidorhombus boscii) and their temporal variations were analyzed. The large sample size, size range and timeseries available allowed obtaining robust somatic parameters of combined sexes for the total weight-length relationships (a=0.0043, b=3.2008), for the gutted weight-length relationships (a=0.0055, b=3.1139), and the weight conversion factors (1.062). They are considered to best fit the current biometric relationships and most appropriate to be used in the stock assessment of the status of the stock and they contribute to a deeper knowledge of the life history traits of this species

Prevalence of the microsporidian parasite Spraguea lophii in white anglerfish (Lophius piscatorius) in the Bay of Biscay and in other Atlantic areas

The white anglerfish (Lophius piscatorius) is an important commercial species in the European fisheries, included those in the Bay of Biscay. This species is infected by the microsporidian parasite Spraguea lophii. Samplings of white anglerfish were performed from a nine year time-series (2006-2014) from Spanish commercial fleet and bottom research surveys operating in southern Bay of Biscay and Galician waters (ICES Div. VIIIc and IXa), Celtic Sea (Div. VIIh), south-western Ireland (Div. VIIj and VIIk), western Ireland and Porcupine Bank (Div. VIIb and VIIc). Length of fish and presence or absence of the parasite were recorded. The prevalence by S. lophii was used to analyse infestation level. This is the first study in which the prevalence of this parasite in relation to the size and sex of the host, as well as its area and catch year, are analyzed in Atlantic. No significant differences were found between sexes of the fish or among years. Differences in parasite infestation level by fish length among areas are discussed. The results were compared with those from the scarce previous studies

Determinación de la posición de la sardina (Sardina pilchardus) en la red trófica pelágica del NO de la Península Ibérica mediante isótopos estables de carbono y nitrógeno

Con el objetivo de estudiar la complejidad de la red trófica pelágica en la zona de afloramiento del N.O. de la Península Ibérica, se midió la abundancia natural de los isótopos estables de carbono y nitrógeno en muestras de plancton (fraccionado en 4 clases de tamaño mediante mallas de 20 a 2000 pm), músculo y estómago de sardina (Sardina pilchardus) y músculo de delfin común (Delphinus delphis). Las diferencias en abundancia isotópica entre los distintos tipos de muestras resultaron más claras utilizando los isótopos de nitrógeno que en el caso del carbono, especialmente en el plancton, observándose una mayor acumulación de los isótopos pesados en los organismos de mayor tamaño. Se encontraron diferencias significativas en la abundancia isotópica del plancton entre la plataforma del S. y la del N. de Galicia, pero sólo al considerar la clase de menor tamaño individual (20-200 pm) También se encontró una mayor acumulación del isótopo pesado del nitrógeno (15N) en el músculo que en el estómago de las sardinas, lo que se corresponde con la mayor tasa de renovación de la materia orgánica en el estómago, y en el músculo de delfín comparado con el de las sardinas, como consecuencia de la mayor longevidad y comportamiento predador de los delfines. El contenido en 15N se incrementa linealmente con el tamaño individual del plancton, pero menos de lo esperable si cada clase de tamaño representase un único nivel trófico, lo que indica que la red trófica pelágica estudiada presenta una complejidad no esperada en un área de afloramiento. En el caso de la sardina, no hay un enriquecimiento claro en los isótopos pesados de carbono y nitrógeno con el tamaño individual enue 11 y 18 cm, pero sí una disminución lineal muy significativa en las sardinas mayores de 18 cm, tanto en ei músculo como en los estómagos. Esto se corresponde con un cambio progresivo desde la rnicrofagia (preferentemente de zooplancton) a la filtración (principalmente de fitoplancton) con el desarrollo de las sardinas. Las diferencias significativas en la abundancia isotópica en el músculo de sardinas entre años y en&e diferentes zonas de la plataforma sugieren que las sardinas dependen de la composición del plancton. Considerando el enriquecimiento en 15N a partir del plancton de menor tamaño considerado, la sardina adulta ocupa un nivel trófico medio entre 1.7 (estómago) y 2.2 (músculo), lo que evidencia su elevada dependencia del fitoplancton. En contraste, los juveniles de sardina presentan una dependencia muy variable de presas del zooplancton

White anglerfish (Lophius piscatorius) in northern Iberian waters and northernmost Atlantic areas: weight-length relationships and other population parameters from a decade of research

The white anglerfish (Lophius piscatorius) is a bottom-living and commercially important species for European fisheries (∼38.000 t in Atlantic waters in 2015). Weight-length relationship, weight conversion factors and condition factor for this species are estimated from a decade (2006-2015) in northern Iberian waters (ICES Div. VIIIc-IXa, southern stock) and in Celtic Seas (ICES Div. VIIb,c,h,j,k, northern stock). A total of 7219 white anglerfish were collected from commercial landings and research surveys and the total length (Lt), total weight (Wt), gutted weight with liver (Wgl) and gutted weight (Wg) were obtained. The weight-length relationships for the combined sexes were: Lt = 0.025 Wt2.853; Lt = 0.02 Wgl2.868; Lt = 0.024 Wg2.861 in Div. VIIIc-IXa, and Lt = 0.027 Wt2.826; Lt = 0.023 Wgl2.825; Lt = 0.023 Wg2.816 in Div. VIIb,c,h,j,k. The commercial landings of this species are available in gutted weight, and therefore the conversion factor (total-gutted weights) was also estimated. All these results can be used in the annual assessment of the state of both stocks in the ICES working group. The condition factor was estimated along the year for immature and mature individuals of each sex and it could provide additional information regarding the spawning season. The results are compared to the previously estimated in other studies