Causes of the seasonal change in diet of the European otter in a closed system for prey

[Resumen] Examinamos una población de nutrias y su alimentación en un medio artificial (un em-balse del NW de la Península Ibérica) encontrando diferencias estacionales en el tipo de presas consumidas estudiando sus excrementos. A pesar de que durante todo el año la presa más prevalente fue el cangrejo rojo americano (Procambarus clarkii), el porcentaje de ciprínidos (carpines Carassius auratus) en la dieta aumentó en el perío-do otoño-invierno (del 15% a 38%). Para establecer las causas de esta estacionalidad determinamos la cantidad de energía que proporciona una presa media de cada tipo (cangrejo y carpín) y el tiempo necesario para su captura y procesado. Aplicando la “Optimal Foraging Theory” concluimos que los crustáceos son una presa menos renta-ble que los ciprínidos y por tanto que su alta frecuencia en la dieta de las nutrias se debe a la menor disponibilidad de peces, especialmente en el período primavera-verano. La baja disponibilidad se debe a la competición interespecífica con otros com-ponentes del gremio de grandes piscívoros del embalse como el cormorán grande (Phalacrocorax carbo) y al ascenso del volumen de agua[Abstract] We studied the foraging ecology of European otters in an artificial habitat (a reservoir located in the NW of the Iberian Peninsula) and found seasonal differences in the type of prey consumed after analyzing their spraints. Although the most prevalent prey item during the whole year was the red swamp crayfish (Procambarus clarkii), cyprinids (goldfish Carassius auratus) percentual prevalence raised during the autumn-winter period (from 15% to 38%). To establish why this seasonality occurs we determined the amount of energy that a mean prey (crayfish and carps) provide and the time needed to both capture and handle each prey type. Applying the optimal foraging theory, we conclude that crustaceans are a less profitable prey compared to cyprinids and thus that their high frequency in otter’s diet is caused mostly by a lower availability of fish, especially during the spring-summer period. Low availability of fish during fall-winter is due to competition with other intra-guild species such as wintering great cormorants (Phalacrocorax carbo), and also due to the increase in water volume stored in the re-servoir during the drier months that makes it more difficult for otters to dive and fish in the bottom.Traballo fin de grao (UDC.CIE). Bioloxía. Curso 2015/201

Reproductive aspects of Donax trunculus (Linnaeus, 1758) in the shellfishing ground of Vilarrube. Implications in fisheries management

Traballo fin de mestrado (UDC.CIE). Bioloxía mariña. Curso 2017/2018[Resumen] En este trabajo se estudia la talla de madurez sexual, el desarrollo gonadal, el ciclo reproductivo y el potencial reproductivo una población de coquina (D. trunculus) en la playa de Vilarrube (Galicia, NO España), que actualmente es el último banco productivo de este recurso en Galicia. Para ello se realizaron muestreos mensuales durante un ciclo anual y se capturaron 3121 ejemplares a los que se midió la longitud de la concha y se definió su estado gonadal en base a su coloración, tamaño relativo y presencia de diferentes estructuras. En la población de coquina estudiada se vio una sex ratio de 1:1, la existencia de varias cohortes diferenciadas y la aparición de nuevos individuos en el mes de octubre. La talla de madurez obtenida en este estudio fue de 14.2 mm. El método empleado para establecer el ciclo gametogénico permitió obtener 7 estados de desarrollo gonadal con los que se acotó un período de desove entre abril y julio. Con los datos obtenidos sobre el potencial reproductivo de la población concluimos que la talla mínima de captura actual no compromete la capacidad reproductiva de D. trunculus.[Abstract] In this study the maturity size, gonadal development, reproductive cycle and reproductive potential of a population of wedge clams (D. trunculus) are studied in Vilarrube beach (Galicia, NW Spain), which is nowadays the last shellfishing ground of this resource in Galicia. For that reason, monthly samplings during an annual cycle were made and 3121 specimens were captured, the length of their shell was measured and their gonad stage was determined based on coloration, relative size and presence of different structures. In this population of wedge clams a sex ratio of 1:1 was observed, as well as the existence of several differentiated cohorts and the appearance of new individuals in October. The obtained size at maturity was 14.2 mm. The method used to stablish the gametogenic cycle allowed to obtain 7 development stages with which a spawning period between April and July was delimited. With the obtained data of the population’s reproductive potential we conclude that the current minimum capture size doesn’t compromise the reproductive capability of D. trunculus

Spatial-temporal variation of the Western Mediterranean Sea biodiversity along a latitudinal gradient

The Mediterranean Sea is a large marine ecosystem with high heterogeneity in both environmental and ecological characteristics. It presents clear gradients from north to south and west to east. It is also an important area in terms of biodiversity and conservation of vulnerable species, and it suffers from several cumulative human impacts, such as fishing and climate change. Previous studies have characterized spatial and temporal patterns of species distributions and biodiversity indicators. However, a comprehensive analysis combining a wide representation of biodiversity indicators is still missing. In this study, we examined spatial and temporal changes of marine communities along a latitudinal gradient over the continental shelf ecosystems (25–500 m depth) of the Western Mediterranean Sea, from the Gulf of Lion in the north to the Gibraltar Strait in the south. We used information from the MEDITS trawl scientific surveys from 1994 to 2018, and we calculated relevant indicators to investigate spatial and temporal patterns in the region. We selected several indicators measuring alpha (species richness, Shannon diversity index and Pielou evenness index) and beta (decomposing both turnover and nestedness) diversity, as well as previously studied indicators identified to be sensitive to fishing and climate change impacts (biomass-based and trophic-level based metrics). We assessed differences in these indicators for the surveyed community as a whole and for fish, crustaceans and cephalopods, separately, over five regions. Our results show clear latitudinal gradients in some indicators: we observe a reversed pattern between richness (decreasing from south to north) and biomass trends (increasing from south to north) for the demersal community. We also found a generalized increase in β-diversity in most regions with time, and a decline in the trophic level of the surveyed community. In addition, we identify a remarkable increase in several indicators when only considering the cephalopods group, and a general low environmental status for the North Catalan Sea. We discuss our results considering the differences between regions and taxa related to the fishing activity and environmental dynamics that can act at different scales. This in-depth analysis illustrates how to use a selection of indicators that combine the capacity to detect ecological changes from regional to sub-regional scales.En prensa2,69

Understanding the Rise of Cephalopods in The Western Mediterranean Using Biodiversity Indicators

VIII International Symposium on Marine Sciences, 6-8 July 2022, Las Palmas de Gran Canaria, EspañaIncreasing impacts of both fisheries and climate change have resulted in changes in the structure, functioning and related ecological metrics of marine communities. A recurrent observation is the rise of cephalopods as fish communities recede. The reason behind this phenomenon is most likely linked with the removal of main predators and competitors by fishing. However, the consequences of climate change (variations in primary production, changes in stratification, and sea warming, among others) may also have an influence due to the high environmental sensitivity and plasticity of cephalopods. Here we aim to unveil the effects of different drivers in the cephalopod community of the Western Mediterranean Sea as well as its differential role in space. We combine several ecological indicators offering a wide range of information about biodiversity, production, trophic structure and relative contribution of prey and predators and relate them with environmental and fisheries drivers of change. The ecological indicators are calculated using data from the MEDITS trawling survey in the region (from the Alboran Sea to the Gulf of Lion) from 2013 to 2019. Our results highlight the response of ecological indicators to several drivers of change and the spatial differences in cephalopod communities with, for instance, higher richness and proportion of predator cephalopods in areas associated to higher SST and fishing effort. Overall, the effect of the environment is greater than the effect of other variables; such results may highlight that under foreseeing scenarios of climate change cephalopods could continue to increase due to increases in sea warmingThis study was partially funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 817578 (TRIATLAS) and No 869300 (FutureMARES). C. Veloy’s contribution was supported by a PhD fellowship from the Spanish Ministry of Education (FPU18/05594) and the University of Barcelona. This work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019- 000928-S). MH and MC also acknowledge support from the COCOCHA project (PID2019- 110282RA-I00, Spanish Ministry of Science and Innovation)Peer reviewe

Spatial-temporal variation of the Western Mediterranean Sea biodiversity along a latitudinal gradient

The Mediterranean Sea is a large marine ecosystem with high heterogeneity in both environmental and ecological characteristics. It presents clear gradients from north to south and west to east. It is also an important area in terms of biodiversity and conservation of vulnerable species, and it suffers from several cumulative human impacts, such as fishing and climate change. Previous studies have characterized spatial and temporal patterns of species distributions and biodiversity indicators. However, a comprehensive analysis combining a wide representation of biodiversity indicators is still missing. In this study, we examined spatial and temporal changes of marine communities along a latitudinal gradient over the continental shelf ecosystems (25–500 m depth) of the Western Mediterranean Sea, from the Gulf of Lion in the north to the Gibraltar Strait in the south. We used information from the MEDITS trawl scientific surveys from 1994 to 2018, and we calculated relevant indicators to investigate spatial and temporal patterns in the region. We selected several indicators measuring alpha (species richness, Shannon diversity index and Pielou evenness index) and beta (decomposing both turnover and nestedness) diversity, as well as previously studied indicators identified to be sensitive to fishing and climate change impacts (biomass-based and trophic-level based metrics). We assessed differences in these indicators for the surveyed community as a whole and for fish, crustaceans and cephalopods, separately, over five regions. Our results show clear latitudinal gradients in some indicators: we observe a reversed pattern between richness (decreasing from south to north) and biomass trends (increasing from south to north) for the demersal community. We also found a generalized increase in β-diversity in most regions with time, and a decline in the trophic level of the surveyed community. In addition, we identify a remarkable increase in several indicators when only considering the cephalopods group, and a general low environmental status for the North Catalan Sea. We discuss our results considering the differences between regions and taxa related to the fishing activity and environmental dynamics that can act at different scales. This in-depth analysis illustrates how to use a selection of indicators that combine the capacity to detect ecological changes from regional to sub-regional scales