STANDARDIZED CATCH RATES OF ALBACORE (THUNNUS ALALUNGA BONNATERRE, 1788) IN THE SPANISH SURFACE LONGLINE FISHERY IN THE WESTERN MEDITERRANEAN IN THE PERIOD 2009-2019

Standardized relative abundance indices of albacore (Thunnus alalunga Bonnaterre, 1788) caught by the Spanish surface longline (LLALB) in the western Mediterranean Sea were estimated for the period 2009-2019. Yearly standardized CPUE were estimated through Generalized Linear Mixed Effects Models (GLMM) under a negative binomial error distribution assumption. The main factors in the standardization analysis were year and season (quarter). The index shows an increasing trend from the beginning of the series (2009) to a maximum in 2011; following a decrease up to 2013, and a relatively stable trend fluctuating around a level three and a half times lower compared to the maximum abundance for the period 2013-2019.En prens

Primer registro de anomalía intersexual gonadal de Trachurus mediterraneus (Steindachner, 1868) desde el Mar de Alborán.

El objetivo principal de este trabajo es dar a conocer el primer registro de una anomalía intersexual gonadal de Trachurus mediterraneus desde el mar de Alborán (Mediterráneo occidental). Este espécimen es el primer registro de intersexualidad para un jurel en el mundo.Postprin

Standardized catch rates for Mediterranean swordfish (Xiphias gladius Linnaeus, 1758) from the Spanish longline fishery. 1988-2017.

Standardized relative abundance indices for swordfish (Xiphias gladius Linnaeus, 1758) caught by the Spanish surface longline in the western Mediterranean Sea were estimated for the period 1988-2017. Standardized CPUEs were estimated through a General Linear Mixed Modeling (GLMM) approach under a negative binomial (NB) error distribution assumption. The main factors in the standardization analysis were fishing area and time of the year (quarter). The standardized index showed notable annual fluctuations without any definite trend for the period under study

Historical and ecological drivers of the spatial pattern of Chondrichthyes species richness in the Mediterranean Sea

Chondrichthyes, which include Elasmobranchii (sharks and batoids) and Holocephali (chimaeras), are a relatively small group in the Mediterranean Sea (89 species) playing a key role in the ecosystems where they are found. At present, many species of this group are threatened as a result of anthropogenic effects, including fishing activity. Knowledge of the spatial distribution of these species is of great importance to understand their ecological role and for the efficient management of their populations, particularly if affected by fisheries. This study aims to analyze the spatial patterns of the distribution of Chondrichthyes species richness in the Mediterranean Sea. Information provided by the studied countries was used to model geographical and ecological variables affecting the Chondrichthyes species richness. The species were distributed in 16 Operational Geographical Units (OGUs), derived from the Geographical Sub-Areas (GSA) adopted by the General Fisheries Commission of the Mediterranean Sea (GFCM). Regression analyses with the species richness as a target variable were adjusted with a set of environmental and geographical variables, being the model that links richness of Chondrichthyes species with distance to the Strait of Gibraltar and number of taxonomic families of bony fishes the one that best explains it. This suggests that both historical and ecological factors affect the current distribution of Chondrichthyes within the Mediterranean Sea.Postprin

STANDARDIZED CATCH RATES FOR MEDITERRANEAN SWORDFISH (XIPHIAS GLADIUS LINNAEUS, 1758) FROM THE SPANISH LONGLINE FISHERY. 1988-2018

Standardized relative abundance indices for swordfish (Xiphias gladius Linnaeus, 1758) caught by the Spanish surface longline in the western Mediterranean Sea were estimated for the period 1988-2018. Standardized CPUEs in number were estimated through a General Linear Mixed Modeling (GLMM) approach under a negative binomial (NB) error distribution assumption. Standardized CPUEs in biomass were estimated through a General Linear Mixed Modeling (GLMM) approach under a log-normal error distribution assumption. The main factors in the standardization analysis were fishing area and time of the year (quarter). The standardized indices showed notable annual fluctuations without any definite trend for the period under studyEn prens

STANDARDIZED CATCH RATES OF ALBACORE (THUNNUS ALALUNGA BONNATERRE, 1788) IN THE SPANISH RECREATIONAL FISHERY IN THE WESTERN MEDITERRARREAN IN THE PERIOD 2005-2019

Catch and effort data from the Spanish recreational fishery in the Balearic Sea (Western Mediterranean) were analysed to estimate an index of relative abundance for albacore for the years 2005-2019. Standardized catch per unit effort (CPUE) in number were estimated through a General Linear Mixed Modeling (GLMM) approach under a negative binomial (NB) error distribution assumption. Nominal catch rates and a standardized abundance index are presented along with estimates of 95% confidence limits of the predicted means. These indices show an upward trend from the start of the series 2005 peaking in 2013; followed by a decrease until 2015. For the latest four-year period (2016-2019), the index shows a relatively stable trend fluctuating around a level two times lower than the maximum abundance recorded in the time series.En prens

Variaciones interanuales en las capturas de tiburones pelágicos en el

Pelagic migrating sharks are by-caught incidentally in longline fisheries. Some of these species have been catalogued as threatened or vulnerable by several Regional Fisheries Organizations and International Conservational NGOs. Alboran Sea is an important area for pelagic migrating sharks because it is the natural and unique communication way between the Atlantic Ocean and Mediterranean Sea. This area is considered by several authors as a hot-spot of Climate Oscillation, such as the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). In addition, Alboran Sea is an important fishing ground where the longline fisheries targeting swordfish operates. Recent studies concluded that historical landing of pelagic sharks from harbours of Alboran Sea and Balearic Sea were mediated for atmospheric oscillations. The main aim of the present study was to assess the effect of atmospheric oscillation on the Catch per Unit Effort (CPUE) of vulnerable sharks thresher shark, Alopias vulpinus (Bonnaterre, 1788) and shortfin mako, Isurus oxyrinchus (Rafinesque, 1810) by-caught in the traditional longline fisheries. The atmospheric oscillations tested in this study were the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). We found a significant positive correlation between the NAO and AO indexes of the previous year to the CPUE tested.En prens

Análisis preliminar del efecto de las oscilaciones climáticas sobre la condición física de la melva (Auxis rochei) post-reproductora en el Mar de Alborán

The Mediterranean Sea is considered by several authors as a hot-spot of Climate Oscillation, such as the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). However, information about the effect of the climate oscillations on the fitness of the species is still scarce. In this context, bullet tuna is an important migratory species with a substantial socio-economical value, whose fisheries might be affected by the effect of certain climatological conditions. In fact, these atmospheric oscillations trigger a chain of hydrodynamic events, leading a change on the timing, destinations, and success of the migratory species in their search for spawning grounds. This study relies on the hypothesis of a correlation between the physical condition of the post-spawning bullet tuna and climate oscillation indexes. For that purpose, 151 individuals of bullet tuna, Auxis rochei, were collected in the traps of Ceuta (Alboran Sea) during three different years, (1983, 1984 and 2014). The physical condition index was calculated, and later statistically correlated with the climate oscillation indexes proposed. Significant differences were found between the physical condition of A. rochei and the average accumulated NAO index. Moreover, for age class 3+ we obtained a significant correlation with atmospheric oscillations.Postprin

Potential factors influencing the condition of demersal sharks in the Mediterranean deep sea ecosystems

The Alboran Sea and the Balearic Islands are two contrasting areas in terms of primary productivity. The former is among the most productive areas of the whole Mediterranean Sea, whereas the Balearic Islands is among the less productive ones in the western Mediterranean. The two areas also show different patterns in the bottom trawl fishing footprint. In the Alboran Sea, the fishing effort on the upper slope is much higher than in Balearic Islands. However, the opposite applies to the middle slope, the vast majority of it remaining unexploited in Alboran Sea, whereas a widespread fishery targeting blue and red shrimp Aristeus antennatus develops in Balearic Islands. Galeus melastomus is a small demersal shark species inhabiting slope bottoms, where adults and juveniles are segregated and concentrate in the middle and upper slope, respectively. It feeds intensively on mesopelagic preys which, in turn, feed on low trophic level organisms close to primary producers. In this work we aimed to study the effect of surface primary production on the condition of deep sea demersal communities. We compared the condition, diet and potential intra- and inter-species competition for feeding resources in the juveniles of G. melastomus between Alboran Sea and Balearic Islands. The comparisons of Le Cren’s relative condition factor, and hepatosomatic and digestivosomatic indices evidenced an opposite pattern to that a priori expectable: better condition in the less productive area. The analysis of stomach contents showed similar diets in both areas, but lower food ingestion in Alboran Sea than in Balearic Islands. Different abundances of potential intra- and inter-specific competitors for feeding resources in the two areas, apparently linked to the different fishing footprints, seems the most likely explanation for the better nourished individuals in Balearic Islands. Whereas juveniles of G. melastomus dominate the shark community in the Balearic Islands upper slope, where the presence of adults of this species is almost negligible, in Alboran Sea this stratum is dominated by adults and potential competitors of other small demersal shark species. All shark species together, including G. melastomus, showed abundances 38% higher in Alboran than in Balearic Islands. Our results show that condition of deep sea demersal fish is ruled by complex inter-relationships among different factors, needing the combination of biological, ecological and fisheries knowledge to understand its variability.En prensa2,42

Segregación espacial por sexo de la tintorera en el Atlántico Este y

The main aim of present study was to analyze the spatial and temporal trends segregation by sex of blue shark (Prionace glauca) in the Eastern Atlantic and Western Mediterranean Sea from the individual bycatches by Spanish surface longline fleet. Our results indicate significant differences in the use of space between males and females. Thus, in low latitudes, within the observed range, sharks are mixed, but from North 38 degree of latitude tend to segregate. In the case of length, a similar pattern is observed, in low longitude sexes appear overlapped, and while to high longitude tend to appear segregated. All these results suggested segregation by sex in the Mediterranean where sharks are grouped in single-sex schools.Postprin