Tiburón pintarroja africana, Galeus polli Cadenat 1959 en las costas de Angola.

Para poder gestionar poblaciones de peces, es necesario conocer la biología de la especie. En el caso de G. polli esta información es escasa y para conocer más sobre los aspectos biológicos de esta especie, se examinaron 1874 ejemplares (791 machos, 1069 hembras y 14 indeterminados), capturados en 11 campañas de pesca científica (2002 a 2013) realizadas en Angola a bordo del Dr. Fridtjof Nansen. El rango de profundidad donde se encontraron fue de 111-808 m, concentrándose entre los 100-200 m (ambos sexos). En general machos y hembras se encuentran en la misma proporción (0.74M:1H), variando con el tamaño del individuo (máximo de 1.57M:1H entre 200-240 mm LT y mínimo de 0.02M:1H para tallas > 350 mm). La talla al nacer se estimó entre 90 y 120 mm. La talla máxima fue de 460 y 350 mm para hembras y machos respectivamente. La talla mínima de madurez sexual para las hembras fue de 200 mm con una L50 de 237 mm y para los machos 170 mm con L50 de 195 mm. La relación talla-peso mostró un crecimiento alométrico negativo en hembras (b=2.945) y machos (b=2.756). Se encontró tanto dimorfismo sexual como segregación por tamaño, implicando medidas de manejo que tomen en cuenta estas diferencias. Los individuos jóvenes se concentran entre 300 y 500 metros de profundidad, los machos maduros entre 100 y 200 m y a partir de 500 m y las hembras maduras a partir de los 600 m

DESARROLLO EMBRIONARIO DEL TIBURÓN PINTARROJA AFRICANA, Galeus Polli CADENAT 1959.

Los ejemplares analizados provienen de 11 campañas de pesca científica (2002 a 2013) realizadas durante el primer semestre de cada año en Angola a bordo del B/O Dr. Fridtjof Nansen. Se examinaron un total de 565 hembras, de las cuales 31 estaban gestando y se les extrajeron los embriones. En el análisis inter-uterino, no hubo diferencias significativas en el número promedio de embriones por útero (3.3), ni en el estado de desarrollo de los embriones, así como tampoco en la relación de sexos (0.81M:1H). La media de embriones por hembra fue de 5.6 (3 a 10) con correlación significativa entre el tamaño de la camada y el de la madre. En base a la observación macroscópica, el desarrollo embrionario uterino se agrupó en 6 estadios: Estadio 1: cápsula fertilizada y vascularizada. El embrión puede no ser visible a simple vista. Estadio 2: embrión visible. Cabeza y ojos prominentes. Filamentos branquiales presentes. Estadio 3: pigmentación alrededor de los ojos. Estadio 4: aletas diferenciadas. Cuerpo parcialmente pigmentado. Estadio 5: cuerpo totalmente pigmentado, filamentos branquiales pequeños. Saco vitelino reducido. Estadio 6: saco vitelino casi totalmente reabsorbido, dientes funcionales. La presencia de embriones en diferentes estados de desarrollo durante un mismo crucero puede indicar un amplio período de apareamiento. La talla estimada de nacimiento está entre 90 y 120 mm. Las estrategias reproductivas son un factor limitante en las pesquerías de elasmobranquios. El entendimiento de su reproducción es vital para el éxito de un manejo adecuado de su pesquería

Towards effort quantification through VMS and observers' data: the case of shrimps trawlers in Mauritanian waters

The Spanish shrimp trawlers is one of the most important fleets operating in Mauritania. They target 3 species: -Penaeus notialis (at 20-80 m depth) -Parapenaeus longirostris (at 100-350 m depth) -Aristeus varidens (at 400-800 m depth) in 3 types of fishing operations that can be carried out during the same day. A critical challenge is to define suitable metrics of effective fishing effort since logbooks only provide information of catches by day. Accurate CPUE obtained from these vessels could be considered good abundance indices of its target stocks, which is of paramount importance for assessment purposes. The objective of this analysis was to use Vessel Monitoring System (VMS) information to robustly infer fleet activity as well as estimate units of effort directed to each of the three target species of the Spanish trawlers operating within the EEZ of Mauritania. The estimates of trawling effort by target species obtained from VMS data show consistency in both values and temporal trends with those registered by observers on-board. The adoption of a consistent method for analysing VMS data will help to ensure that calculations of trawling effort are repeatable and comparable among studies

Climatic oscillations effect on the yellowfin tuna (Thunnus albacares) Spanish captures in the Indian Ocean

The yellowfin tuna (Thunnus albacares) (YFT) is among the eight marine species with the highest catches globally. The Spanish purse seine freezer fleet operating in the Indian Ocean is one of the most important YFT fishing fleets in the world. The South Oscillation Index (SOI), Pacific Decadal Oscillation (PDO), and Indian Ocean Dipole (IOD) are interrelated, and have combined effects in the Indian Ocean. Moreover, Madden–Julian Oscillation (MJO) is the dominant component of intraseasonal variability in the tropical Indian and Pacific oceans where the sea surface is warm. The main aim of present study is to understand the effect of these four climatic oscillations on Spanish purse seine YFT catches in the Indian Ocean. The ultimate goal is to estimate the specific time lag of the effect of each climatic oscillation on the YFT catches for management purposes. To estimate this, we adjusted different General Additive Models between the response variable (corrected YFT catches per unit of effort per year), compared to a combination of SOI, PDO, IOD, and MJO lagged up to 8 years. Our results suggest that there is a lagged effect modulated mainly by PDO-SOI, which could be related to a good recruitment, larval survival, or improved spawning. Thus, negative PDO phase (or positive SOI phase) lagged between 3 and 6 years could favor future stock abundance, while positive PDO phase (or negative SOI phase) lagged 3 or 6 years could negatively affect future stock abundance.Versión del edito

Effect of climatic oscillations on small pelagic fisheries and its economic profit in the Gulf of Cadiz

Several studies have shown the effect of climatic oscillations on fisheries. Small pelagic fish are of special global economic importance and very sensitive to fluctuations in the physical environment in which they live. The main goal of this study was to explore the relationship between the North Atlantic Oscillation (NAO), the East Atlantic pattern (EA), and the Arctic Oscillation (AO) on the landings and first sale prices of the most representative small pelagic commercial species of the purse-seine fisheries in the Gulf of Cadiz (North East Atlantic), the European anchovy Engraulis encrasicolus and the European sardine Sardine pilchardus. Generalised linear models (GLMs) with different data transformations and distribution errors were generated to analyse these relationships. The best results of the models were obtained by applying a moving average of order 3 to the dataset with a double weighted median. Our results demonstrate relationships between NAO, AO, and EA and European anchovy and sardine landings. These cause an indirect effect on the first sale price in markets through catch variations, which affect the price according to the law of supply and demand. The limitations of this study and management implications are discussed.Postprint2,5

Discards from a deep-sea shrimp fishery in Angolan waters (SW Africa)

A programme of observers on board Spanish shrimp trawlers in Angola was initiated by IEO in 2018 in order to improve the scientific information required by Sustainable Management of External Fishing Fleets (SMEFF Regulation of the EU). In this context, discard studies are considered very relevant, both for assessment purposes and for obtaining information on adverse ecological impacts in marine ecosystems. Most fishing hauls performed during the observed period November 2018 to December 2019 were carried out at depths between 384 and 649 m, with classic bottom otter trawl targeting the striped red shrimp Aristeus varidens. Discards accounted for 60% of the total catch during the analysed period. The estimated global discard rate for 2019 (2.2 discard/retained catch) indicates that 1915 tonnes of retained catch produced 4213 tonnes of discards, of which a small amount is of commercial species, as A. varidens (3.8 tonnes) and Merluccius polli (153 tonnes). A total of 131 discarded species were identified, with the highest group contribution being fish (70%), followed by crustaceans (20%). The most abundant species in discard weight were Ariomma melanum, Lamprogrammus exutus, Chaunax pictus, Centroscymnus owstonii, Hoplostethus cadenati, Lophius vaillanti, Yarrella blackfordi and Ariomma bondi (all together accounting for 55% of discards). The most frequent species were H. cadenati and L. exutus, discarded in 95% of the analysed fishing hauls. Discards estimations of commercial species obtained through a long-term observers program might result in improving the assessments of main commercial species from Angolan deep sea waters

Growth of the deep water rose shrimp Parapenaeus longirostris in Mauritanian waters (NW Africa)

The deep water rose shrimp Parapenaeus longirostris is the main target species of a Spanish fleet of shrimp bottom trawlers operating in the Mauritanian EEZ. The life history of this species is well known in north eastern Atlantic and Mediterranean waters, while the information is quite limited for the eastern central Atlantic. Biological samplings of the species were conducted by scientific observers onboard this fleet, from catches obtained during 17 fishing trips performed between March 2014 and June 2019. The carapace lengths (CL) of 91662 specimens (54% females and 46% males) were grouped in 33 monthly length frequency distributions. For the study of the length–age relationship, the Von Bertalanffy Growth Function (VBGF) was fit to the monthly length distributions by using the ELEFAN I routine followed by separating the frequency histograms into normal components through the Bhattacharya’s method and the NORMSEP routine. These analyses were carried out separately for males, females, and combined sexes, using the FISAT II automatic calculation program. CL of females and males ranged from 11.6 to 39.2 mm and 10.5 to 30.5 mm, respectively. Three and five modal components (annual cohorts) were identified for females and males, respectively. The growth function estimated parameters were CL∞=41.74, k=0.51 for combined sexes, CL∞= 41.67, k= 0.51 for females and CL∞= 32.24, k=0.84 for males. Estimated growth performance indices were around 2.95 for combined sexes, females and males. The estimated parameters may be used as input to test length-based methodologies for the assessment of this data-limited stock, for which only production models have been used so far

Long term oscillations of Mediterranean sardine and anchovy explained by the combined effect of multiple regional and global climatic indices

This study is a contribution to the PELWEB project (“Winners, losers and shifts of PELagic food WEB changes in the western Mediterranean Sea: from ecosystem consequences to future projections”, CTM2017-88939-R,2018–2020), and to “Fostering the capacity of marine ecosystem models to PROject the cumulative effects of global change and plausible future OCEANS” (PROOCEANS): Funding by Ministerio de Ciencia e Innovación, Proyectos de I+D+I (RETOS-PID2020-118097RB-I00).It is widely known that the abundance and distribution dynamics of populations of small pelagic clupeid fish, such as sardines and anchovies, are affected by large-scale climate variability, which may lead to changeovers to new regimes of small pelagics. However, long-distance climatic oscillations, such as El Niño/La Niña and the Pacific Decadal Oscillation, have been little explored in the Western Mediterranean Sea. We investigated the possible effects of the South Oscillation Index (i.e. the atmospheric oscillation coupled with the El Niño/La Niña) and Pacific Decadal Oscillation on fluctuations in catches of European anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the Western Mediterranean Sea, and their association with regional climate oscillations (i.e. the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, the Western Mediterranean Oscillation index, and the Arctic Oscillation)