Expertos del IEO y del INRH (Marruecos) actualizan la evaluación del voraz del estrecho de Gibraltar

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When non‑target wildlife species and alien species both affect negatively to an artisanal fishery: the case of trammel net in the Alboran Sea

In the Northern Alboran Sea, artisanal small-scale fisheries using trammel nets suffer economic losses, and local fishermen see their way-of-life endangered, due to interactions with wildlife species such as alien species and dolphins. On the one hand, the alien seaweed Rugulopteryx okamurae, which was first recorded in the Alboran Sea in 2015, has undergone an intensive expansion in the sub-region, monopolizing the available seabed, causing radical changes in the underwater seascape and clogging the trammel nets. On the other hand, the damage caused to the fishing nets by dolphin fish predation is an ancient problem worldwide, but it is intensifying in the last years. The main objective of this study is to understand the main environmental and technical conditions that favor damages of fishing trammel nets in the Alboran Sea, which entails an important loss of catchability, due to (i) the clogging of the artisanal fishing trammel nets by invasive seaweed, and (ii) the breaking of the nets by dolphin predation. Through close monitoring of fishermen in port, we obtained direct information of 548 sets. Our results indicate that approximately 30% of trammel sets suffered a damage due to unwanted interaction with alien seaweeds and dolphins. As seaweeds invasion is a global problem while dolphin-fishing gear interaction is more local, we concluded that only a large-scale management of exotic algae, together with the involvement of local fishermen, could solve the economic problems of this activity.This study has been financed by MAVA Foundation through an agreement between ACCOBAMS (Agreement on the Conservation of Cetaceans of the Black Sea, Mediterranean Sea and Contiguous Atlantic Area) and the Spanish Herpetological Society (AHE, Asociación Herpetológica Española), under the project: “CETAFISHBE, Interactions between air breathing marine vertebrates, particularly cetaceans, and artisanal fisheries in northern` Alboran Sea”. We thank the fishermen, skippers and shipowners who have helped us during this study. We also recognize the support provided by the fishermen’s associations from the ports of Caleta de Vélez and Fuengirola (Southern Spain). We are grateful for the comments of anonymous reviewers who improved a previous paper version. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature

DIFFERENTIAL TEMPORAL AND SPATIAL DISTRIBUTION OF ADULT LOGGERHEAD SEA TURTLES FROM GULF OF CÁDIZ TO WESTERN MEDITERRANEAN SEA

The aim of this paper was to search for and model spatial and seasonal trends in occurrences (stranding or by-catches) of adult loggerhead turtles in the western Mediterranean area and Gulf of Cádiz (Atlantic) independently of their origin. Adult turtles were only bycaught on longlines from May to August. Adults were stranded in the eastern and western areas of the Strait of Gibraltar threshold throughout the year. In the Gulf of Cádiz (Atlantic), strandings were significantly concentrated in May and June, whereas in the Alboran Sea (Mediterranean), strandings mainly occurred in June and July. The probability of catching a mature loggerhead increases during June and July south of the Balearic Islands. The results suggest that adult loggerhead turtles move (migrate) from the Atlantic area (Gulf of Cádiz) to the Mediterranean (Alboran Sea) from May to June, and subsequently move to the Balearic Sea from June to July. These results are in line with those obtained by previous studies.Postprin

Factors Associated with the Differential Distribution of Cetaceans Linked with Deep Habitats in the Western Mediterranean Sea

Deep-habitat cetaceans are generally difficult to study, leading to a limited knowledge of their population. This paper assesses the differential distribution patterns of three deep-habitat cetaceans (Sperm whale—Physeter macrocephalus, Risso’s dolphin—Grampus griseus & Cuvier’s beaked whale—Ziphius cavirostris). We used data of 842 opportunistic sightings of cetaceans in the western Mediterranean sea. We inferred environmental and spatio-temporal factors that affect their distribution. Binary logistic regression models were generated to compare the presence of deep-habitat cetaceans with the presence of other cetacean species in the dataset. Then, the favourability function was applied, allowing for comparison between all the models. Sperm whale and Risso’s dolphin presence was differentially favoured by the distance to towns in the eastern part of the western Mediterranean sea. The differential distribution of sperm whale was also influenced by the stability of SST, and that of the Risso’s dolphin by lower mean salinity and higher mean Chlorophyll A concentration. When modelling the three deep-habitat cetaceans (including Cuvier’s beaked whale), the variable distance to towns had a negative influence on the presence of any of them more than it did to other cetaceans, being more favourable far from towns, so this issue should be further investigated.Postprint2,92

Tuna regional fisheries management organizations and the conservation of sea turtles: a reply to Godley et al

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Análisis temporal de varamientos de tortuga laúd, Dermochelys

Leatherback sea turtle (Dermochelys coriacea, Vandelli, 1761)) is a large migratory species reproducing in Atlantic areas and abundant in the Mediterranean Sea, where nesting beaches do not exist. Leatherback stranding occasionally occurs in the Andalusia coasts (183 turtles during 1990- 2011 period). This communication study a possible inter and intra annual temporal patterns in leatherback strandings in the area and analyze the effects of atmospheric oscillations on their arrivals in the Mediterranean. The North Atlantic Oscillation (NAO) plays an essential role in climate fluctuations affecting the North Atlantic and associated biological components. Recent studies showed that the Arctic Oscillation (AO) is highly correlated with NAO, explaining more accurately variations found in ecological time series. The summer months concentrate significatively a higher number of leatherback turtle strandings. Moreover, the results show a significant negative correlation between the stranding frequency and the average rate of the AO.Postprin

Coexistencia y uso diferencial del mar Mediterráneo occidental por las especies residentes de pequeños delfínidos.

En el mar Mediterráneo occidental coexisten tres especies residentes de delfines: el delfín común (Delphinus delphis), el delfín listado (Stenella coeruleoalba) y el delfín mular (Tursiops truncatus). La situación de los delfines en este área puede representar un caso especial de simpatría, ya que estas especies son relativamente similares y están amenazadas, por lo que la competencia entre ellas podría conllevar problemas adicionales. Se hace, por tanto, necesario investigar el complejo patrón de coexistencia parcial y uso diferencial parcial de las aguas entre estas especies. Desde el punto de vista de la biogeografía de la conservación, es un desafío determinar cómo estas tres especies de delfines conviven y evitan la exclusión competitiva en el contexto de dichas amenazas. El Instituto Español de Oceanografía dispone de un conjunto de datos de avistamientos oportunistas de especies de delfines. Utilizando estos datos, construimos tres variables binarias, que consisten en el avistamiento de una especie frente al avistamiento de cualquiera de las otras dos especies. Obtuvimos tres modelos de probabilidad significativos en función de un conjunto de variables explicativas espacio-temporales. Para analizar estos modelos desde la perspectiva de la teoría de conjuntos borrosos, se aplicó la función de favorabilidad a los modelos de probabilidad, así como las operaciones borrosas de superposición y entropía. Los resultados muestran que los delfines comunes están favorecidos de manera diferencial en la parte oriental del área de estudio y en áreas alejadas de las principales rutas de navegación. Los delfines listados están favorecidos de manera diferencial en la parte occidental del área de estudio, sobre aguas profundas, cerca de las principales rutas de navegación y en verano y primavera. Por último, los delfines mulares están favorecidos de manera diferencial en la parte medio-occidental del área de estudio, en invierno y sobre aguas poco profundas.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Length–weight relationships of kitefin shark Dalatias licha, and little sleeper shark Somniosus rostratus from the western Mediterranean Sea, and long snouted lancetfish Alepisaurus ferox from the eastern North Atlantic Ocean

This paper provides length-weight relationships (LWR) for three species: long snouted lancetfish Alepisaurus ferox, kitefin shark Dalatias licha and little sleeper shark Somniosus rostratus. Samples were collected occasionally from 2009 to 2013. A total of 49 D. licha and 24 S. rostratus samples from the western Mediterranean Sea, and 211 samples of A. ferox from the eastern North Atlantic Ocean were recorded for LWR. For each species, regression coefficients and parameters “a” and “b” were calculated with 95% confidence interval. The LWR parameter b for all species ranged from 2.889 to 3.5048, with R2 ranging from 0.717 to 0.823.Postprin

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

Preliminary Analysis for Identification of Priority Species of Small Pelagic Shared Stocks in GSA01 And GSA03 (Alborán Sea)

Small pelagic resources and particularly sardine (Sardina pilchardus) and anchovy (Engraulis encrasicholus) represent an important fishery activity for the countries bordering the Alboran Sea. This paper aims at contributing to the identification of priority species of small pelagic shared stocks in GSA01 and GSA03 (northern and southern Alboran Sea GFCM regions) for carrying out joint stock assessments and promoting new management measures that would allow the sustainability of the resources and its exploitation. The WG on small pelagic shared stocks met twice during 2011 progressing in analysing the available data on the stocks and its exploitation and building a common data base. Moreover a comparative analysis on sardine landings data from 2003-2010 in GSA01 and GSA03 was carried out explaining that the exploitation pattern in sub-areas (GSAs 01 and 03) is different but the total length-frequency distribution of sardine exploited by each country appears to be similar. A tentative in applying a LCA analysis of the Moroccan and Spanish data on sardine using different biological parameters and with the VIT software was unsuccessful but orientated for future works of the W