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

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

Preliminary data on the ovarian histological structures observed in black hakes (M. polli and M. senegalensis) off Mauritania

The black hakes, Merluccius polli and M. senegalensis, are target species of a trawl Spanish fleet in Mauritanian waters. M. polli is a deep-water hake while M. senegalensis shows a shallower distribution. Both species are mixed in the landings, although the deeper hake totals a greater fraction (85%) of the catch due to the fishing strategy of the trawl fleet. The female gonads of both hakes were collected during an experimental survey carried out in the Mauritanian EEZ. Mature ovaries were examined from the start of the reproductive season in this area. Ovaries were processed by a standard histological technique. Histological characteristics of ovarian tissues and oocyte stages were studied by light microscopy. The ovaries of black hakes showed various stages of oocyte development from the small sized, chromatin nuclear and perinucleolar oocytes, and the medium sized, cortical alveoli and vitellogenic oocytes. This last stage presents yolk granules occupying the cytoplasm at different levels. In the case of M. senegalensis, the presence of large sized oocytes with early migration of the nucleus to the animal pole, as well as fusion of oil droplets indicate maturation and imminent spawning, thus, indicating an earlier spawning than M. polli. Furthermore, postovulatory follicles observed in M. senegalensis indicate a recent batch spawning episode. This result is concordant with the values of GSI obtained for both species in these waters. The reproductive period extends from October to Mars with a defined peak in December - January for females of both hakes, although the shallower species, M. senegalensis, shows an earlier spawning in this study. Atretic stages were observed, but their incidence was low because the sampling corresponds to the beginning of the spawning period. The species are multiple batch spawners as suggested by their oocyte size frequency distribution in the ovary. The present study is a first approach to ovarian histology of M. polli and M. senegalensis, and intended to provide basic knowledge for further detailed studies on the reproductive biology of these species, essential for an adequate assessment of this stock.Instituto Español de Oceanografía (IEO

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

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

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

Macroscopic and microscopic maturity stages. living working document for small tuna species.

Maturity ogives are usually estimated using different methods, including macroscopical and microscopical maturity data. Differences in maturity ogives estimations are found for species and by area/stock. So those differences may be a consequence of the use of different methodological techniques (criteria) or due to different spawning tactics. Taking this into account is essential to guarantee that the maturity criteria for each species are consistent across the laboratories and countries involved in stock assessment. The objective of this document is to show a large amount of detailed photos (macro and microphotographs) of the different gonad stages of Auxis rochei, Sarda sarda and Euthynnus alletteratus, for females and males, which will be an enhancement to the descriptions of maturity stages given in the maturity tables

Análisis de las tendencias de las capturas de atún listado Katsuwonus pelamis (Linnaeus, 1758) de la pesca deportiva en el Mediterráneo occidental (2006-2014)

Skipjack tuna, Katsuwonus pelamis is a tropical tuna species that inhabits the warm waters worldwide. This species is caught as bycatch of tuna fisheries in the Mediterranean Sea whereas a variety of fisheries target skipjack tuna in the three oceans. This species is a resource of high economic value for many countries and information about its basic life history parameters, distribution and catches is available, however that information in the Mediterranean Sea is scarce. The main objective of this study was to test for interannual variability in the catches of this species in two areas: the Balearic Sea and its surroundings (area I), and the Alboran Sea (area II). Catch per unit effort of skipjack tuna (both in number and kilograms) from individuals caught by recreational fisheries was assessed. Our results indicate that the occurrence of skipjack tuna in fishing area II is larger than those found in fishing area I. Nevertheless, larger individuals were caught in fishing area I, coinciding with the spawning season. Finally, the CPUE of skipjack tuna was tested against two explanatory variables (area and year) using a general linear model (GLM). Our results conclude that these variables explain the 58% of the variability of the catches of this species in the studied areas, where an increasing trend of captures was found. Despite the limitations of the present study, our results showed evidence of an increment of the skipjack tuna abundance in the spawning ground of other tuna species.En prens

ÁREA DE PUESTA DEL LISTADO Katsuwonus pelamis, ATÚN TROPICAL, EN EL MEDITERRÁNEO OCCIDENTAL

El listado Katsuwonus pelamis es una especie de gran importancia comercial, cuyas capturas representan el 58.1% de las capturas globales de todas las especies de túnidos (FAO, 2019). Aunque el listado es una especie tropical, que principalmente se reproduce en aguas a temperaturas que exceden los 24ºC, las capturas en el mar Mediterráneo son frecuentes, especialmente en las últimas décadas. El Mediterráneo occidental, concretamente el mar Balear, es una zona de puesta para diversas especies de túnidos. El listado es capturado en esta área por la pesquería comercial y deportiva. En este trabajo los individuos muestreados fueron capturados por la pesca deportiva en campeonatos de pesca de altura celebrados en junio y julio en el mar Balear y en agosto y septiembre en el mar de Alborán durante el periodo 2014-2019. El sex ratio (n= 340) de listados (46.5 - 81 cm FL) fue de 1:0.9 (H:M). Se pesaron las gónadas de 329 individuos y su madurez macroscópica asignada, 201 gónadas fueron examinadas histológicamente. El análisis del índice gonadosomático y el examen de las gónadas evidencian que el listado se encuentra reproductivamente activo en el mar Balear (Mediterráneo occidental) coincidiendo en área y época de puesta con el atún blanco Thunnus alalunga. Estos resultados indican que el listado ha ampliado tanto su rango de distribución como sus áreas de puesta. Además, su monitorización es de interés por la su posible impacto sobre otras especies con las que comparte tanto área de distribución como área de puesta en el Mediterráneo occidental