Essential ocean variables and high value biodiversity areas: Targets for the conservation of marine megafauna

Effective conservation and management measures are needed to face the unprecedented changes that marine ecosystems, and particularly marine megafauna, are suffering. These measures require the identification of highvalue biodiversity areas (HVBAs) which in turn require the identification of the essential ocean variables (EOVs) that shape the environmental envelope of communities (i.e. space defined by a set of environmental variables). The aim of this study was to delineate and characterise the HVBAs for the north and northwestern Spanish seabird and cetacean community taking advantage of the sightings collected during the annual PELACUS oceanographic survey (2007–2016). We used distance sampling methodology to analyse the species detectability based on environmental conditions. Then, we delimitated the HVBAs and identified the EOVs defining the environmental envelope of the community based on a spatio-temporal modelling approach using Generalized Additive Models. Overall, the main environmental variables driving species abundance were the sea surface temperature (SST), the distance to the shelf-break and the chlorophyll-a concentration (Chl-a). The SST and Chla were identified as dynamic EOVs due to their highest relative predictor importance, driving the environmental envelope and shaping areas of higher density. HVBAs were located mainly over the northwestern Spanish waters and decreased towards the inner Bay of Biscay remaining spatially stable over the study period. By identifying community-level HVBAs, we can understand the underlying ecological and oceanographic processes driving the spatio-temporal patterns of biological communities, such as those composed by seabirds and cetaceans. This information would identify conservation targets to assist the allocation of management resources. In addition, the location of HVBAs can help to fulfil the emergent need for sound spatial information to support the implementation of marine spatial planning.En prens

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

Nuevos conocimientos sobre la invernada y migración de la gaviota báltica Larus fuscus fuscus Linnaeus, 1758 (Charadriiformes: Laridae) en España

La gaviota sombría, Larus fuscus (Linnaeus, 1758), es una especie politípica cuya situación taxonómica sigue siendo revisada por parte de algunos científicos. La subespecie nominal Larus fuscus fuscus o “gaviota báltica” está considerada rareza en España, aunque desde hace más de una década cada año es observado algún ejemplar anillado. Esto nos ha llevado a actualizar su distribución espacial y temporal en España, usando datos de aves cuyos registros han sido aprobados o están bajo revisión del Comité de Rarezas de la Sociedad Española de Ornitología. Nuestros resultados sugieren que España constituye un área de invernada para una parte muy pequeña de la población, especialmente el área de Málaga, y que el período con mayor probabilidad de avistamientos es el de noviembre a marzo.Postprin

North Atlantic oscillation affects the physical condition of migrating bullet tuna Auxis rochei (Risso, 1810) from the Western Mediterranean Sea

Climate oscillations exert direct control over the environment in which they occur and may influence the physical condition of migratory marine species, such as tuna, as reported by several authors. The main aim of thisstudywastoexploretheassociationbetweenthepotentialeffectsoftheNorthAtlanticOscillation(NAO)on thefitness condition of bullet tuna (Auxis rochei) migrating to the Spanish Mediterranean Sea. A total of 2357 length-weight pairs of data obtained from individuals collected on the Spanish Mediterranean coast were analysed. A non-parametric Spearman test was used to investigate correlations between the atmospheric oscillation indexes and two physical condition indexes. The results suggest that, in general, positive phases of the NAO index improve the physical condition offish migrating to spawning grounds in the Mediterranean Sea. These results could be explained by changes in the dominant winds, which could favour pre-spawning migration, and by nutrients availability, which guarantees their recovery after the spawning period.En prens

Assessing the Environmental Status of the short-beaked common dolphin (Delphinus delphis) in North-western Spanish waters using abundance trends and safe removal limits

Monitoring and assessment of the status of marine mammal populations is a requirement of the European Marine Strategy Framework Directive (MSFD). Due to the difficulty of collecting data in the marine environment and because many populations of these highly mobile species inhabit waters of several Member States, monitoring of marine mammals is particularly challenging. In the present work we have used a 10- year time-series of data collected from multidisciplinary research surveys to estimate common dolphin (Delphinus delphis) abundance and trends in continental shelf waters of the northwest Spanish sub-region. We argue that this approach provides a valuable addition to large-scale dedicated surveys, offering a shorter interval between surveys and hence offering the possibility to track abundance changes at a regional scale. Trends in the number of dolphins present in the study area over the last 10 years show a mean increase of about 9.6% per year, which results in an evaluation of Good Environmental Status for the species in the area using the abundance indicator adopted in the framework of the MSFD. Data obtained from dedicated dual-platform surveys have been used to correct the detection bias in our data collected using single-platforms (attraction toward the observation platform and animals missed on the track-line), to obtain absolute abundance estimates for calculating bycatch limits. The average abundance over the study period was 12831 dolphins [CI 95%; 9025, 18242] calculated with the conventional distance sampling methodology, 4747 [3307, 6816] corrected for attraction and missed animals on the track-line, and 22510 [15776, 32120] corrected only for missed animals on the track-line. The estimated safe bycatch limit for this area calculated from these abundance values were 218 [153, 310], 81 [56, 115] and 383 [268, 546] per year, respectively. Comparing these figures with estimates based on different sources, the percentage of dolphins that die in this study area is higher than the maximum limit allowable under the OSPAR criteria for population mortality adopted as an indicator for the MSFD.Versión del editor3,26

EFFECTS OF ICCAT Rec [2016-05] SIZE REGULATION ON THE DISCARDS OF THE SPANISH LONGLINE FISHERY TARGETING SWORDFISH (Xiphias gladius Linnaeus, 1758) IN THE WESTERN MEDITERRANEA

The ICCAT Commission, at its meeting on November 2016, approved a multi-annual recovery plan for the Mediterranean swordfish starting in 2017 and continuing through 2031 (ICCAT Rec [2016-05]). Among other provisions, the recovery plan proscribed a minimum landing size (MLS) of 100 cm (lower-jaw fork length- LJFL), which is 10 cm higher than the previously implemented (ICCAT Rec [2013-04]). The aim of this study is to assess the effect of the recently implemented MLS on the swordfish discarding activities by the Spanish surface longline fishery operating in the western Mediterranean for the period 2015-2017. Our results show that: i) as compared to the former MLS (ICCAT Rec [2013-04]), a higher percentage of undersized dead fish is now discarded at sea, with the additional risk that does not be reported and taken into consideration during the assessment of the stock; ii) the amount of fishing effort (number of hooks) for fulfilling the allocated quota has increased; iii) the fishing season must be longer to achieve the allocated quota. Both the increase in fishing effort and the lengthening of the fishing season have an adverse effect on the economic profitability of the surface longline fleet without achieving the intended reduction in the fishing mortality exerted on the juvenile fraction of the Mediterranean swordfish stock

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

Abundance and distribution of the common dolphin (Delphinus delphis) in the north of the Iberian Peninsula

Common dolphin s ( Delphinus delphis ) are one of the most abundant species of small cetacean in Northeast Atlantic Ocean and the most abundant in Atlantic shelf waters of the Iberian Peninsula. However, the abundance , distribution and population trends in the recen t years of this species are poorly known , but such information is needed to develop population dynamic models . Thus far, the only absolute abundance estimate in the shelf Atlantic waters of the Iberian Peninsula was obtained in 2005 during the SCANS - II survey. Along the north and northwest coast s of the Iberian Peninsula , t he Spanish Institute of Oceanography has carried out annual acoustic survey s to estimate pelagic fish biomass for the last two decades. Since 2007 , an observer program for top predators has been integrated in to these survey s , collecting sightings on cetaceans, seabirds and other species using line - transect method ology . Common d olphin sightings from 2007 to 201 4 were analyzed with Distance software to estimate relative population size . Because attraction to the vessel could inflate population estimates, c ommon dolphin a bundance was estimated using a detection function only from sightings where no attraction were recorded and also using Bayesian methods to combine previou s data on attraction collected during SCANS - II with data collected from the acoustic fish surveys. D olphin density estimated with both methods w as < 0.3 dolphin s/ Km 2 , which is similar to the density estimated by SCANS - II . T he Bayesian framework allows us to work with the scarcity and uncertainty of the data , particularly when obtaining annual estimates. Because c etacean sightings were collected during fish acoustic surveys , pelagic fish abundance ( e.g. S ardine and Blue whiting ) , obtained concurrently to the sightings, can be used , along with other environmental variables , to model dolphin habitat and to predict dolphin abundance and distribution

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