As lontras-marinhas escolhem as suas presas de acordo com o valor nutricional?

Mestrado em Ecologia AplicadaA Teoria do Forrageio Ótimo propõe que o estímulo nutricional na escolha de presas e busca de alimento em carnívoros é o ganho energético. Em contraste, pesquisas recentes sugerem que os carnívoros selecionam presas que fornecem uma dieta com um equilíbrio específico de macronutrientes (gordura, proteína, hidratos de carbono), ao invés do maior conteúdo energético. Para este efeito, as escolhas de presas de lontras-marinhas (Enhydra lutris) que habitam Sitka Sound no sudeste do Alasca, foram estudadas durante os meses de maio a agosto de 2016. Os objetivos desta pesquisa foram: 1) descrever a dieta das lontras-marinhas em Sitka Sound; 2) descrever o valor nutricional das suas presas; 3) comparar diferenças na escolha de presas de acordo com o sexo; e 4) avaliar e comparar o valor nutricional das presas com as escolhas das lontras-marinhas. Os dados de observação foram coletados oportunisticamente, através de uma plataforma de oportunidade. As presas de lontras-marinhas foram capturadas em áreas arbitrárias de Sitka Sound, e analisadas quanto à sua percentagem em lípidos (teor de gordura) e calorias (densidade de energia). O consumo de presas foi significativamente diferente: as amêijoas foram as presas mais consumidas (68,6%), seguidos pelos ouriços-do-mar (14,3%), vieiras (5,7%), pepinos-do-mar (5,7%), caranguejos (2,9%) e estrelas-do-mar (2,9%). Além disso, os resultados revelaram uma significativa diversidade no conteúdo de gordura e densidade energética entre presas de lontra-marinha. O abalone registou maior teor de densidade energética, seguido pelas vieiras, enquanto que os ouriços-do-mar registaram maior teor em lípidos. A escolha de presas e a ingestão de nutrientes não diferiram significativamente entre machos e fêmeas, no entanto, os machos de lontras-marinhas consumiram mais moluscos do que as fêmeas, enquanto que as fêmeas consumiram mais ouriços-do-mar do que os machos. O trabalho sobre nutrição em carnívoros é preliminar, e estes resultados fornecem um ponto de partida para futuras pesquisas. As respostas a estas questões não só terão implicações significativas na gestão das populações de predadores e das comunidades ecológicas de que fazem parte, mas também acrescentarão informações importantes sobre a biologia de predadores que até agora foram negligenciadas. Além disso, os conflitos nas comunidades sobre os impactos que as lontras-marinhas têm na pesca comercial no sudeste do Alasca, não podem ser ignorados. Compreender as escolhas de presas de lontras-marinhas pode fornecer previsões de como a pesca pode ser afetada, de acordo com o crescimento da população de lontras nesta área, a fim de ajudar políticos, membros da comunidade e pescadores comerciais, a responder em conformidade.Foraging theory proposes that the nutritional driver of prey choice and foraging in carnivores is energy gain. In contrast, recent research suggests that carnivores select prey that provides a diet with a specific balance of macronutrients (fat, protein, carbohydrates), rather than the highest energy content. To this effect, the prey choices of sea otters (Enhydra lutris) inhabiting Sitka Sound, in southeast Alaska, were studied during the months of May-August of 2016. The goals of this research were to 1) describe sea otter’s diet in Sitka Sound; 2) describe the nutritional value of sea otters’ prey items; 3) compare differences in prey choice according to sex; and 4) evaluate and compare prey’s nutritional value with sea otter’s prey choices. Foraging observational data were collected opportunistically on a boat-based platform of opportunity. Sea otter’s main prey were captured in arbitrary areas of Sitka Sound, and analyzed for percentage in lipids (fat content), and calories (energy density). Prey consumption was significantly different: clams were the most frequently consumed prey (68,6%), followed by sea urchins (14,3%), scallops (5,7%), sea cucumbers (5,7%), crabs (2,9%) and sea stars (2,9%). Also, the results revealed a significant diversity in content of fat and energy density between sea otter prey specimens. Abalone ranked first on content of energy density, followed by scallops, while sea urchins recorded the highest lipid content. Prey choice and nutrient intake were not significant different between male and female sea otters, nevertheless, males consumed more clams than females, while females consumed more sea urchins than males. The work on carnivore nutrition is preliminary, and these results provide a starting point for future work. Answers to such questions not only will have significant implications for managing predator populations and the ecological communities of which they are a part, but will also add important information on predator biology that has been neglected so far. Moreover, communities’ conflicts over the impacts sea otters are having on commercial shellfisheries in southeast Alaska cannot be overlooked. Understanding sea otter’s prey choices may provide information and predictions of how fisheries may be affected as the sea otter population grows in this area, in order to help decision makers, policy makers, community members, and commercial fishermen respond accordingly

Trends in cetacean research in the Eastern North Atlantic

We acknowledge funds provided by the Science and Technology Foundation (FCT) through strategic projects UID/MAR/04292/2019, UIDB/00329/2020, and UIDB/05634/2020. TAM received partial support through the project UIDB/00006/2020. RP is supported by an FCT grant (SFRH/BPD/108007/2015). BCM is supported by FCT through grant PD/BD/140845/2018. FA received financial support from projects M1420‐09‐5369‐FSE‐000001 and M1420‐01‐0145‐FEDER‐000001‐OOM.1. Cetaceans are considered ecosystem engineers and useful bioindicators of the health of marine environments. The Eastern North Atlantic is an area of great geographical and oceanographic complexity that favours ecosystem richness and, consequently, cetacean occurrence. Although this occurrence has led to relevant scientific research on this taxon, information on the composition of this research has not been assessed. 2. We aimed to describe and quantify the evolution of research on cetaceans in the Eastern North Atlantic, highlighting the main focal areas and trends. 3. We considered 380 peer-reviewed publications between 1900 and 2018. For each paper, we collected publication year, research topics and regions, and species studied. We assessed differences among regions with distinct socio-economic landscapes, and between coastal and oceanic habitats. To evaluate the changes in scientific production over time, we fitted a General Additive Model to the time series of numbers of papers. 4. Although research in this region has been increasing, the results show relatively little research output in North African and coastal regions within the study area. Moreover, except for four studies, research was restricted to a few miles around the coast of the main islands, leaving offshore regions less well surveyed. There was little research on genetics, acoustics, and behaviour. Most papers were focused on the Azores and Canary Islands, and mostly involved Tursiops truncatus, Delphinus delphis, and Physeter macrocephalus. Species considered Endangered or Near Threatened were the subjects of only 10% of the studies. 5. We suggest a greater research focus on beaked whales (Ziphiidae) in Macaronesia, as well as collaborative efforts between research teams in the region, by sharing data sets, and aiming to produce long-term research. Moreover, a Delphi method approach, based on questionnaires answered by experts, could be attempted to identify priority research for cetaceans in these areas.PostprintPeer reviewe