Diet of the horned octopus Eledone cirrhosa in Atlantic Iberian waters: ontogenetic and environmental factors affecting prey ingestion

13 páginas, 2 figuras, 3 tablasGrowing concern over sustainability of some fisheries has led to a shift in the focus of fisheries management, from a single-target species towards an ecosystem-based management. This process involves identification a suite of indicators, among which ontogenetic and environmental factors affecting prey ingestion should be considered. The present study combines morphological and molecular analysis of stomach contents and Multinomial Logistic Regression (MLR) to understand the dietary regime and factors affecting it in Eledone cirrhosa inhabiting Atlantic Iberian waters. Specimens were collected monthly from commercial bottom trawl multispecies fisheries between February 2009 and February 2011 in three fishing grounds (North Galicia, West Galicia and North Portugal). Based on stomach analysis, E. cirrhosa ingested mainly crustaceans, followed by teleost fish, echinoderms, molluscs and polychaetes. Molecular analysis of 14 stomach contents confirmed the visual identification of prey items as well as cannibalistic events. Statistical tests found that sex and body weight did not significantly affect prey selection, while season, fishing ground and maturity stage of the animals had a significantly effect on the probability of selecting a particular prey. The ecological implications of MLR modelling results are discussedThis research was supported by the project “Impacto do ambiente sobre o polbo Eledone cirrhosa no sistema de afloramento costeiro das augas de Galicia” (INCITE08PXIB402074PR), funded by Xunta de Galicia. Marcos Regueira was supported by a FCT Grant (SFRH/BD/51038/2010)Peer reviewe

Biomasa potencial y distribución de pulpo en el este del banco de Campeche (Yucatán, México)

10 pages, 2 tables, 4 figures.-- This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License[EN] The octopus fishery on the Campeche Bank (Yucatán, Mexico) is considered the third largest in the world. In Yucatán, two fleets target this resource: an artisanal fleet and a semi-industrial fleet. The artisanal fleet only catches Octopus maya, while the semi-industrial fleet catches two species, O. maya and O. “vulgaris” Type II, because it operates at deeper waters (>30 m). Since there is no information on the abundance of O. “vulgaris” Type II, management is based only on O. maya. In order to generate information about the abundance of this species, four fishing research cruises were carried out in the northeastern area of the continental shelf off the Yucatán Peninsula. Four methods (a stratified random method, a swept area, geostatistics and a weighted swept area) were applied and compared to determine the instantaneous abundance and biomass of both species in the study area. The lowest potential biomass was calculated with the geostatistical method, with values between 18.5% and 36.7% lower than the other three methods. O. “vulgaris” Type II showed the lowest biomass (37.8±3.36 t) during May and July and the highest (189.56±11.6 t) in December. Our findings revealed that the total abundance of both species was similar in the study area, with a geographic overlap whose amplitude changed throughout the year according to the geographic position: O. maya dominated at approximately 88°W, while O. “vulgaris” Type II dominated towards the southeast at 87°W.[ES] La pesquería de pulpo en el banco de Campeche (Yucatán, México) se considera la tercera productora mundial de pulpo. En Yucatán, dos flotas capturan este recurso: una flota artesanal y una semi-industrial. La flota artesanal solo captura Octopus maya, mientras que la flota semi-industrial captura dos especies: O. maya y O. “vulgaris” Tipo II. Esto se debe a que la flota semi-industrial opera en aguas más profundas (>30 m). Dado que no existe información sobre la abundancia de O. “vulgaris” Tipo II, el manejo se basa únicamente en la evaluación de O. maya. Con objeto de generar información sobre la abundancia de esta especie, se realizaron cuatro campañas de prospección pesquera en la zona noreste de la plataforma continental de la Península de Yucatán. Se aplicaron cuatro métodos (método aleatorio estratificado, área barrida, geoestadística y área barrida ponderada) y sus resultados se compararon para determinar la abundancia y biomasa instantáneas de ambas especies en el área de estudio. La biomasa potencial más baja se obtuvo con el método geoestadístico, con valores de 18.5 a 36.7% más bajos que con los otros tres métodos. O. “vulgaris” Tipo II mostró una biomasa más baja (37.8±3.36 t) durante mayo y junio, mientras que la más alta (189.56±11.6 t) fue en diciembre. Nuestros hallazgos revelaron que la abundancia total para las dos especies fue similar; además ambas especies presentaron una superposición geográfica, cuya amplitud cambió con el período del año y la posición geográfica: O. maya fue dominante en la longitud de los 88°W, mientras que O. “vulgaris Tipo II dominó hacia el sudeste de la plataforma de Yucatán (aproximadamente 87°W)The results of this study were obtained as part of the project “Distribución, reproducción, biomasa y patrones de movimiento del pulpo común Octopus vulgaris Cuvier, 1797 en la costa de Yucatán”, with financial support from the Consejo Nacional de Ciencia y Tecnología (grant number 237057)Peer reviewe

Biomass and distribution of the red octopus (Octopus maya) in the northeast of the Campeche Bank

7 pages, 3 figures, 1 tableThe regulatory framework of the red octopus (Octopus maya) fishery includes total allowable catches (TAC), which are based on studies conducted on the population that occurs in shallow waters. In fact, most of the biological studies of this species refer to the fraction of the population that occupies waters less than 30 m deep; however, O. maya can occur up to a 60 m depth. The aim of this study is to assess the stock of O. maya that occupies waters between 30 m and 60 m deep. Four research cruises were carried out during the closed and fishing seasons, from May 2016 to January 2017. An average of 29 sampling sites were surveyed in each cruise (±2 sampling sites) using a commercial vessel with a uniform sampling effort. In each sampling site, the swept area, the total number of octopuses captured, the total weight of the catch, and the individual weight of octopuses were recorded. Biomass was obtained with four methods: stratified random method, swept area method, geostatistical biomass model, and an unpublished method of weighted swept area. The four methods provided consistent results. The distribution pattern of species was in patches, although before the fishing season started it was more homogeneous. The fraction of the population that occurs between 30 m and 60 m deep consisted mostly of adult organisms, so it could be contributing significantly to the recruitment of the entire population, even to the fraction that is exploitedThe results of this study were obtained as part of the project Distribución, reproducción, biomasa y patrones de movimiento del pulpo común Octopus vulgaris Cuvier, 1797 en la costa de Yucatán with financial support of the Consejo Nacional de Ciencia y Tecnología (grant number 237057)Peer reviewe