ASSESSING THE APPLICABILITY OF ENVIRONMENTAL INDICATORS FOR IMPROVING THE FISHERIES ASSESSMENT OF THE ALBACORE (Thunnus alalunga) UNDER THE A4A APPROACH

In this study we explore the potential for improving the stock assessment of Mediterranean Albacore by integrating environmental indicators. For this purpose we developed a catch at age model within the A4A stock assessment approach. The input data was similar to that used in the official SCRS stock assessment in 2017 but with an updated larval index. The environmental indicator provides information on the interannual variability of the sea surface temperature in the Balearic Sea during the spawning season, and it is included in the “Environmental pressure” component of the Ecosystem Report Card. The indicator is included in the assessment model in different ways, as index of the class age 0, as vector for the Stock/recruitment model, and as productivity value in other stock recruitment models (Ricker, Beverton-Holt). The results showed that incorporating the environmental variability indicators provide a better stock assessment fits (AIC, BIC), and also show the need for more advanced techniques to test stock assessment performance when testing the inclusion of environmental variability

Stereological comparison of oocyte recruitment and batch fecundity estimates from paraffin and resin sections using spawning albacore (Thunnus alalunga) ovaries as a case study.

Traditional histological protocols in marine fi sh reproductive laboratories using paraf fi n as the embedding medium are now increasingly being replaced with protocols using resin instead. These procedures entail differ- ent degrees of tissue shrinkage complicating direct comparisons of measurement results across laboratories or articles. In this work we selected ovaries of spawning Mediterranean albacore ( Thunnus alalunga ) as the subject of our study to address the issue of structural changes, by contrasting values on oocyte recruitment and fi nal batch fecundity given from the same tissue samples in both paraf fi nandresin.Amodernstereologicalmethod, the oocyte packing density (OPD) theory, was used supported by initial studies on ovarian tissue sampling and measurement design. Examples of differences in the volume fraction of oocyte stages, free space and connective tissue were found between the embedding media. Mean oocyte diameters were smaller in paraf fi nthaninresin with differences ranging between 0.5% in primary growth and 24.3% in hydration (HYD) stage oocytes. Fresh oocyte measurements showed that oocytes shrank as a consequence of the embedding process, reaching the maximaldegreeofshrinkageforoocytesintheHYDstage(45.8%inparaf fi nand26.5%inresin).Inordertoassess the effect of oocyte shrinkage on the OPD result, and thereby on relative batch fecundity (F r ), oocyte diameters corrected and uncorrected for shrinkage, were used for estimations. Statistical signi fi cant differences were found ( P b 0.05) between these two approaches in both embedding media. The average F r was numerically smaller in paraf fi n compared to resin (86 ± 61 vs. 106 ± 54 oocytes per gram of body mass (mean ± SD)). For both embedding media statistical signi fi cant differences ( P b 0.05) were seen between F r results based on either oocytes in the germinal vesicle migration stage or HYD stage. As a valuable adjunct, the present use of the OPD theory made it possible to document that the oocyte recruitment of spawning ovaries of Mediterranean albacore followed the typical pattern of an asynchronous oocyte development and indeterminate fecundityPostprint2,444

Updated standardized joint CPUE index for bluefin tuna (Thunnus thynnus) caught by Moroccan and Spanish traps for the period 1981- 2012.

Relative abundance indices of bluefin tuna (Thunnus thynnus) caught by the Moroccan and Spanish traps in the area close to the Strait of Gibraltar were estimated for the period 1981- 2013. Standardized CPUEs were estimated through a General Linear Modeling (GLM) approach under a negative binomial error distribution assumption.Versión del edito

UPDATED STANDARDIZED CATCH RATES IN NUMBER FOR SWORDFISH (Xiphias gladius L.) CAUGHT BY THE SPANISH LONGLINE FLEET IN THE MEDITERRANEAN SEA, 1988- 2013

A General Linear Modeling (GLM)approach to analysis of variance was used to analyze swordfish logged catch rates in number of fish from 24 , 239 trips carried out by the Spanish surface longline fleet addressed to this species in the Western Mediterranean f or the period 1988 - 2013.Postprin

ASSESSING THE APPLICABILITY OF ENVIRONMENTAL INDICATORS FOR IMPROVING THE FISHERIES ASSESSMENT OF THE ALBACORE (THUNNUS ALALUNGA) UNDER THE A4A APPROACH

In this study we explore the potential for improving the stock assessment of Mediterranean Albacore by integrating environmental indicators. For this purpose we developed a catch at age model within the A4A stock assessment approach. The input data was similar to that used in the official SCRS stock assessment in 2017 but with an updated larval index. The environmental indicator provides information on the interannual variability of the sea surface temperature in the Balearic Sea during the spawning season, and it is included in the “Environmental pressure” component of the Ecosystem Report Card. The indicator is included in the assessment model in different ways, as index of the class age 0, as vector for the Stock/recruitment model, and as productivity value in other stock recruitment models (Ricker, Beverton-Holt). The results showed that incorporating the environmental variability indicators provide a better stock assessment fits (AIC, BIC), and also show the need for more advanced techniques to test stock assessment performance when testing the inclusion of environmental variabilityEn prens

UPDATED STANDARDIZED JOINT CPUE INDEX FOR BLUEFIN TUNA (THUNNUS THYNNUS) CAUGHT BY MOROCCAN AND SPANISH TRAPS FOR THE PERIOD 1981- 2011

Relative abundance indices of bluefin tuna (Thunnus thynnus) caught by the Moroccan and Spanish traps in the area close to the Strait of Gibraltar were estimated for the period 1981- 2011. Standardized CPUEs were estimated through a General Linear Modeling (GLM) approach under a negative binomial error distribution assumption.Postprin

Updated standardized catch rates in number and weight for swordfish (Xiphias gladius L.) caught by the Spanish longline fleet in the Mediterranean Sea, 1988- 2013.

A General Linear Modeling (GLM) approach to analysis of variance was used to analyze swordfish logged catch rates in number of fish from 24,239 trips carried out by the Spanish surface longline fleet addressed to this species in the Western Mediterranean for the period 1988 -2013.Versión del edito

Preliminary management strategy evaluation for blue shark in the Indian Ocean using a data-limited approach

In tuna-RFMOs there has been an effort to move to quantitative stock assessments for pelagic sharks, especially for the main species such as blue shark Prionace glauca. In IOTC, blue shark was last assessed in 2017 with the use of an integrated length-based age-structured model (SS3). This paper now presents a preliminary exercise with data-limited Management Strategy Evaluation (MSE) to test options for different potential management procedures (MPs), using the data-limited methods toolkit (DLMtool). Reference points have not yet been adopted for sharks in IOTC, so for this exercise we set some tentative reference points noting that those can be updated in the future as needed. Eighty-nine MPs were evaluated with 9 considered potentially acceptable. Options and tradeoffs between those MPs are shown and described in the paper. We have focused mainly on trade-offs between biomass and yield, but according to the management objectives agreed other performance metrics can be applied. Even thought this is a preliminary exercise at this point, we hope that it provides initial thoughts and opens the discussion for the advancement of the blue shark management and conservation in the Indian Ocean

Environmental variablity in three major Mediterranean tuna spawning grounds.

We propose four different environmental indicators, three related to temperature variability in three major spawning grounds of tuna species in the Mediterranean, and one related to the sea surface salinity variability in the Balearic Sea. These oceanographic indicators show the annual variability of environmental parameters affecting growth and survival of tuna eggs and larval. The indicators are intended to provide quick access to assessment working groups and fisheries scientist to identify potentially anomalous year

Biological aspects of little tunny Euthynnus alletteratus from Spanish and Portuguese waters.

This study provides information on some biological aspects of Euthynnus alletteratus from the western Mediterranean (Spanish coast) and in the Atlantic Ocean (south of Iberian Peninsula). A total of 1266 individuals were measured between 2003 and 2017. The L-W relationship was calculated with W equal to 0.01242 FL3.058 . Histological analysis of the ovaries and the monthly variation of the gonadosomatic index for both sexes suggested that the spawning season for Euthynnus alletteratus in the western Mediterranean Sea takes place from June to August. The lengths at first maturity (L50) were estimated to be 50.1 cm and 43.4 cm FL for female and male, respectively. Age at first maturity (A50) was calculated