Lipid (energy) reserves of european hake (Merluccius Merluccius) in the North-Western Mediterranean

This study analyses for the first time the lipid (energy) reserves of European hake (Merluccius merluccius) in the north-western Mediterranean from an ecophysiological perspective. Results show that there is a progressive accumulation of lipids in the liver of maturing hake -where the bulk of the fat is stored- as individuals grow. Results also indicate that female pre-spawners expend much energy on reproductive activities since they present lower liver lipid reserves than juveniles and maturing individuals. Furthermore, results show that female pre-spawners with higher lipid reserves in their livers had a higher amount of lipids in their ovaries, suggesting that maternal condition (spawner quality) may affect the reproductive potential of hake. Overall, the results of this study suggest that the analysis of liver lipid reserves during pre-spawning, along with the evaluation of the gonadosomatic index and the consideration of the reproductive stage, can contribute to improve the estimation of the reproductive potential of gadoid species such as hak

Lipid reserves of red mullet (Mullus barbatus) during pre-spawning in the northwestern Mediterranean

Lipid reserves are a particularly important attribute of fishes because they have a large influence on growth, reproduction and survival. This study analyses the lipid content of red mullet (Mullus barbatus) pre-spawners in three different areas of the northwestern Mediterranean in relation to trawling activities and river runoff. The muscle lipid was considered as an indicator of the somatic condition of individuals whilst the gonad lipid was used as a proxy of the energy invested in reproduction. The results show that fish with the highest muscle lipid levels inhabited the area where fishing impact was lowest. Since the abundance and biomass of polychaetes, which represent the main food source for red mullet, were found to be lower in trawled zones than in unfished ones, we suggest that differences in the muscle lipid levels between areas might be attributed to variation in prey abundance in relation to fishing impact. However, no impact of river runoff on lipid reserves of red mullet was observed. The results also show that muscle and gonad lipid reserves are not related to each other during pre-spawningLas reservas lipídicas constituyen un importante atributo de los peces porque juegan un papel destacado en su crecimiento, reproducción y supervivencia. Este estudio analiza las reservas lipídicas del salmonete de fango (Mullus barbatus) durante la prepuesta en tres áreas diferentes del Mediterráneo noroccidental en relación a la actividad pesquera y las descargas fluviales. Se ha considerado el contenido lipídico en el músculo y en la gónada como indicadores de la condición somática y de la energía invertida en la reproducción de los individuos respectivamente. Los resultados muestran cómo los peces con una cantidad mayor de lípidos en el músculo habitan el área donde el impacto pesquero es menor. Puesto que la abundancia y la biomasa de poliquetos, que constituyen la principal fuente de alimento del salmonete de fango, son inferiores en las zonas afectadas por el arrastre que en las zonas donde no se practica este tipo de pesca, se sugiere que las diferencias en la cantidad de lípidos en el músculo entre las distintas áreas podrían atribuirse a las diferencias en la abundancia de presas, lo cual podría guardar relación con la actividad pesquera. Sin embargo, no se observa impacto alguno de las descargas fluviales sobre las reservas de lípidos del salmonete de fango. Los resultados también muestran cómo los contenidos lipídicos en el músculo y en la gónada de los ejemplares no están relacionados entre sí durante la prepuesta de la especi

Presentació del seminari

Presentació del Seminari a càrrec de Josep Calbó, Vicerector de Recerca de la UdG, i Josep Lloret i Margarida Casadevall, coordinadors del Seminar

Effects of artisanal fisheries on the scorpaenids (Scorpaena spp.) reproduction in the marine protected area of Cap de Creus (NW Mediterranean)

Rockfish species are considered important to the ecology of rocky-reef communities which constitute a key habitat in many coastal marine protected areas (MPAs). These species, which are commercially valuable for artisanal fisheries in the Mediterranean, display particular biological traits that could render them vulnerable to fishing. In this study we monitored the artisanal fisheries of scorpaenids (Scorpaena spp.) in the MPA of Cap de Creus (northwestern Mediterranean) in order to estimate the status of their populations, to link captures with the reproduction of these species, and to evaluate the potential impact that artisanal fishing may have on them. Data from onboard sampling with artisanal fishermen and from fisheries statistics (total landings) were used. Total landings and catch per unit of effort (CPUE) follow a clearly seasonal cycle, with a prominent peak during the summer months coinciding with their spawning season, which may be due to mating behavior prior to fertilization. Although maximum sizes are bigger inside the MPA than in non-protected areas situated close by, a significant percentage of individuals caught inside the MPA are below their size at sexual maturity. Although rockfish seem to be favored by the partial protection of the MPA, the allowed artisanal fisheries are probably impacting the reproduction of these specie

Canvi de papers: estudiant actor, professor observador

El treball discuteix per una banda com incrementar el treball personal i la responsabilitat dels estudiants en les classes pràctiques de laboratori i per altra banda quins problemes nous representa aquest treball pels professors i quines competències que es requeririen, amb la finalitat de moure l’activitat més cap a un procés d’aprenentatge de l’estudiant i reduint la funció promotora i de lideratge del professor. A part dels continguts, es fomenta la participació activa i s’incrementa el treball de competències transversals dels estudiants: aprendre per ensenyar, planificació, tasques de supervisió, capacitat de negociació, treball en grup, comunicació oral, argumentació i per sobre de tot responsabilitat. Valorar els resultats resulta de moment difícil i contradictori. Per una banda la taxa d’èxit i de rendiment de l’assignatura ha tendit a la baixa, tot i que la valoració de l’assignatura depèn no només d’aquesta activitat, i en aquesta en concret el rendiment és alt. Per l’altre, la valoració que fan els estudiants de l’assignatura és molt positiva, de manera que l’exigència i el sistema d’avaluació continuada, força estricte, no ha comportat una pèrdua d’interès per la matèria. Per part dels professors hi ha un sobreesforç de preparació de les pràctiques perquè s’han hagut de modificar els guions i el material, i un sobreesforç d’avaluació, atès que es fa una avaluació qualitativa i la seva justificació resulta particularment difícil per falta d’experiència. En general aquest tipus d’avaluació no és acceptada fàcilment i genera molta discussió sobre quina ha de ser la manera de fer-ho per no caure en la subjectivitat. El debat avui dia hauria de ser, també, com s’ha de produir la formació del professorat. Finalment, sembla haver-hi una millora en el rendiment dels estudiants que han participat en el pla d’acció tutorial de la facultat de cièncie

Links between parasitism, energy reserves and fecundity of European anchovy, Engraulis encrasicolus, in the northwestern Mediterranean Sea

The European anchovy, Engraulis encrasicolus L. 1758, is one of the most sought-after target species in the northwestern Mediterranean Sea. However, this stock currently consists of small individuals, and landings are reported to have decreased considerably. The main purpose of this study was to assess, for the first time, the interrelationships between size, fecundity, energy reserves and parasitism in female anchovies, in order to analyse the potential implications for the health of northwestern Mediterranean anchovy stocks arising from the current shortage of large individuals. Results revealed that smaller individuals show lower fecundity, lower lipid content and a higher intensity of certain parasites. As it is known that smaller individuals now predominate in the population, the relationships found in this study indicate that the health of anchovies from the northwestern Mediterranean is currently impairedThis work was supported by the Spanish Ministry of Science and Innovation (research project ref. CTM2009-08602). D.F.-M. benefited from a Formación de Personal Investigador predoctoral fellowship (ref. BES-2010-032618) and J.L. benefited from a ‘Ramón y Cajal’ research contract from the Spanish Ministry of Economy and Competitivenes

Health and reproduction of red mullet, Mullus barbatus, in the western Mediterranean Sea

The reproductive and general health of exploited fish stocks is an essential element of sustainable and profitable fisheries. The main purpose of this study was to assess the relationships between reproduction and two important parameters of fish health (parasitism and energy reserves) in female specimens of red mullet, Mullus barbatus, from the western Mediterranean Sea. We present new data for this species on (i) the prevalence and intensity of infection by metazoan parasites; (ii) the total lipid content in muscle and gonads as a measure of condition and (iii) fecundity and egg quality as a measure of their reproductive capacity. The results show that M. barbatus is a batch spawner with an income breeding strategy, an asynchronous development of oocytes and indeterminate fecundity. The results also indicate that the three most abundant and prevalent parasites significantly affect the condition and reproduction of M. barbatus. Specifically, the digenean, Opecoeloides furcatus, causes a reduction in the female"s energy reserves, while the nematodes, Hysterothylacium fabri and H. aduncum, produce a rise in egg production but impair egg quality. These implications of the relationships between parasitism, fish health and fish reproduction should be taken into consideration in the assessment and management of exploited specie

Parasitism, condition and reproduction of the European hake (Merluccius merluccius) in the northwestern Mediterranean Sea

It is well known that parameters relating to physical condition and reproduction of fish provide essential data for estimating the productivity of exploited populations, as is the case with the European hake (Merluccius merluccius) in the northwestern Mediterranean Sea. Although parasitism might affect these parameters, research in this area is very scarce (and in the case of the Mediterranean almost non-existent). This study evaluates for the first time the potential link between parasitism, condition and reproduction of the European hake. Indicators of fish energy reserves (total lipid content in liver and gonads) and reproductive capacity (fecundity, egg quality and atresia) were evaluated, as were the prevalence and intensity of infection by metazoan parasites. The results indicate that the impact of anisakid nematodes is mostly negative and occurs mainly when hake are allocating their energy reserves to gonadal development. Although the results reveal a link between parasitism, condition and reproduction, we concluded that the northwestern Mediterranean hake population is in equilibrium with its metazoan parasites, which are not causing severe impairment to their physical condition or reproductive capacit

Variability of physical factors relevant to fisheries production in the Mediterranean Sea, North Sea and Baltic Sea

Recent publications have shown that river runoff and wind mixing are two major environmental factors affecting productivity of fish populations in subtropical and tropical areas, as opposed to water temperature in colder waters. In the present paper, we compare the variability of seawater temperature, river runoff and wind mixing in three different seas: a subtropical sea (the Mediterranean) and two cold seas (the North Sea and the Baltic). Temperature variability decreased from colder to warmer areas. The highest temporal variability in the river runoff corresponded to rivers flowing into the Mediterranean, and the lowest corresponded to rivers flowing into the North Sea and the Baltic Sea. The variability in the wind mixing index (cube of the wind speed) depended on the area under consideration, and attained maximum values in the Cap Béar station (northwestern Mediterranean). The effect of these regional variability differences in environmental factors on fisheries production is briefly discussedInvestigaciones recientes demuestran que las descargas fluviales y los vientos son factores ambientales clave para la productividad de las poblaciones explotadas en zonas subtropicales y tropicales, mientras que en mares fríos la temperatura del agua constituye el factor ambiental más importante para la productividad pesquera. Este estudio compara las diferencias geográficas en la variabilidad temporal de tres factores físicos (temperatura del agua, aportes fluviales y velocidad del viento) en un mar subtropical (Mediterráneo) y dos mares fríos (Mar del Norte y Báltico). La variabilidad temporal de la temperatura del agua es mayor en los dos mares fríos que en el subtropical. Así mismo, los ríos que desembocan en el Mediterráneo presentan mayor variabilidad temporal en cuanto a los aportes fluviales que los ríos que desembocan en el Mar del Norte y el mar Báltico. La variabilidad temporal en el índice de mezcla del viento (velocidad del viento al cubo) es distinta según la zona que se considere, y es máxima en la estación de Cap Béar (Mediterráneo noroccidental). Finalmente, se discuten los efectos de esta variabilidad ambiental geográfica sobre las poblaciones explotada

Body reserves mediate trade-offs between life-history traits: new insights from small pelagic fish reproduction

Limited resources in the environment prevent individuals from simultaneously maximizing all life-history traits, resulting in trade-offs. In particular, the cost of reproduction is well known to negatively affect energy investment in growth and maintenance. Here, we investigated these trade-offs during contrasting periods of high versus low fish size and body condition (before/after 2008) in the Gulf of Lions. Female reproductive allocation and performance in anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) were examined based on morphometric historical data from the 1970s and from 2003 to 2015. Additionally, potential maternal effects on egg quantity and quality were examined in 2014/2015. After 2008, the gonadosomatic index increased for sardine and remained steady for anchovy, while a strong decline in mean length at first maturity indicated earlier maturation for both species. Regarding maternal effects, for both species egg quantity was positively linked to fish size but not to fish lipid reserves, while the egg quality was positively related to lipid reserves. Atresia prevalence and intensity were rather low regardless of fish condition and size. Finally, estimations of total annual numbers of eggs spawned indicated a sharp decrease for sardine since 2008 but a slight increase for anchovy during the last 5 years. This study revealed a biased allocation towards reproduction in small pelagic fish when confronted with a really low body condition. This highlights that fish can maintain high reproductive investment potentially at the cost of other traits which might explain the present disappearance of old and large individuals in the Gulf of Lion