Thermal stratification drives movement of a coastal apex predator

A characterization of the thermal ecology of fishes is needed to better understand changes in ecosystems and species distributions arising from global warming. The movement of wild animals during changing environmental conditions provides essential information to help predict the future thermal response of large marine predators. We used acoustic telemetry to monitor the vertical movement activity of the common dentex (Dentex dentex), a Mediterranean coastal predator, in relation to the oscillations of the seasonal thermocline during two summer periods in the Medes Islands marine reserve (NW Mediterranean Sea). During the summer stratification period, the common dentex presented a clear preference for the warm suprathermoclinal layer, and adjusted their vertical movements following the depth changes of the thermocline. The same preference was also observed during the night, when fish were less active. Due to this behaviour, we hypothesize that inter-annual thermal oscillations and the predicted lengthening of summer conditions will have a significant positive impact on the metabolic efficiency, activity levels, and population dynamics of this species, particularly in its northern limit of distribution. These changes in the dynamics of an ecosystem’s keystone predator might cascade down to lower trophic levels, potentially re-defining the coastal fish communities of the futureVersión del editor2,92

Longer and less overlapping food webs in anthropogenically disturbed marine ecosystems: confirmations from the past

The human exploitation of marine resources is characterised by the preferential removal of the largest species. Although this is expected to modify the structure of food webs, we have a relatively poor understanding of the potential consequences of such alteration. Here, we take advantage of a collection of ancient consumer tissues, using stable isotope analysis and SIBER to assess changes in the structure of coastal marine food webs in the South-western Atlantic through the second half of the Holocene as a result of the sequential exploitation of marine resources by hunter-gatherers, western sealers and modern fishermen. Samples were collected from shell middens and museums. Shells of both modern and archaeological intertidal herbivorous molluscs were used to reconstruct changes in the stable isotopic baseline, while modern and archaeological bones of the South American sea lion Otaria flavescens, South American fur seal Arctocephalus australis and Magellanic penguin Spheniscus magellanicus were used to analyse changes in the structure of the community of top predators. We found that ancient food webs were shorter, more redundant and more overlapping than current ones, both in northern-central Patagonia and southern Patagonia. These surprising results may be best explained by the huge impact of western sealing on pinnipeds during the fur trade period, rather than the impact of fishing on fish populations. As a consequence, the populations of pinnipeds at the end of the sealing period were likely well below the ecosystem's carrying capacity, which resulted in a release of intraspecific competition and a shift towards larger and higher trophic level prey. This in turn led to longer and less overlapping food webs

Impacte ecològic de les llevantades sobre les comunitats de fons rocosos: el cas del temporal Gloria

9 pages, 4 figuresL’impacte del temporal Gloria als fons rocosos litorals que es troben entre 0 i 50 m de fondària depèn bàsicament de l’exposició a l’onatge i de l’estabilitat del substrat, però també de la susceptibilitat dels organismes a l’abrasió per les partícules de sediment posades en moviment per les onades (Mateo i Garcia-Rubies, 2012). La vulnerabilitat dels hàbitats també està molt relacionada amb l’exposició a l’onatge (segons la localització geogràfica, l’orientació i la fondària), la tipologia del substrat (roca contínua, blocs, sorres) i les característiques morfològiques i biològiques dels organismes que el formen (Mateo i Garcia-Rubies, 2012). Això explica que els impactes siguin molt variables en funció de la fondària i dels trets vitals de les espècies dominants. Així, les comunitats dominades per espècies que presenten dinàmiques molt ràpides, amb una elevada taxa de creixement i reclutament, tindran una capacitat de recuperació més elevada que les dominades per espècies de dinàmiques més lentes com, per exemple, les espècies estructurals del coral·ligenPeer reviewe

Spatial variability of fish fauna in sheltered and exposed shallow rocky reefs from a recently established Mediterranean Marine Protected Area

Coastal exposure may affect the structure of littoral fish assemblages. To evaluate its effects, fish assemblages associated with shallow (0-3 in depth) rocky reefs were investigated by visual census at the Asinara Island National Park (northwestern Sardinia, Italy, Mediterranean Sea) during autumn 2003. Distribution patterns of ichthyofauna in sheltered and exposed rocky reefs were assessed over the spatial scales of locations (i.e. kilometres) and sites (i.e. hundreds of metres). Overall, 38 fish taxa belonging to 17 families were recorded, with Labridae, Sparidae and Serranidae being the families with the most species. Univariate analyses showed that the average density of Labridae and Serranidae was significantly greater at sheltered locations, while particulate organic matter feeders (i.e. Mugilidae) were more abundant at the exposed ones. Significant differences in species richness, total fish abundance and densities of Labridae and planktivorous fish were observed at the spatial scale of sites. Multivariate analyses revealed that whole fish assemblages differed more at the scale of locations than among sites. Planktivorous species contributed most to the dissimilarity between fish assemblages associated with exposed and sheltered stretches of coast. Direct and indirect effects of coastal exposure were hypothesized to explain the potential role of wave action in structuring fish assemblages associated with shallow rocky reefs. In particular, direct effects could affect the distribution patterns of fish, depending on their swimming ability, while indirect effects could include changes in the benthic cover (especially macroalgae) caused by wave action, which then had a repercussion on the fish

Longer and less overlapping food webs in anthropogenically disturbed marine ecosystems: confirmations from the past

The human exploitation of marine resources is characterised by the preferential removal of the largest species. Although this is expected to modify the structure of food webs, we have a relatively poor understanding of the potential consequences of such alteration. Here, we take advantage of a collection of ancient consumer tissues, using stable isotope analysis and SIBER to assess changes in the structure of coastal marine food webs in the South-western Atlantic through the second half of the Holocene as a result of the sequential exploitation of marine resources by hunter-gatherers, western sealers and modern fishermen. Samples were collected from shell middens and museums. Shells of both modern and archaeological intertidal herbivorous molluscs were used to reconstruct changes in the stable isotopic baseline, while modern and archaeological bones of the South American sea lion Otaria flavescens, South American fur seal Arctocephalus australis and Magellanic penguin Spheniscus magellanicus were used to analyse changes in the structure of the community of top predators. We found that ancient food webs were shorter, more redundant and more overlapping than current ones, both in northern-central Patagonia and southern Patagonia. These surprising results may be best explained by the huge impact of western sealing on pinnipeds during the fur trade period, rather than the impact of fishing on fish populations. As a consequence, the populations of pinnipeds at the end of the sealing period were likely well below the ecosystem's carrying capacity, which resulted in a release of intraspecific competition and a shift towards larger and higher trophic level prey. This in turn led to longer and less overlapping food webs

The effects of marine protected areas on ecosystem recovery and fisheries using a comparative modelling approach

17 pages, 11 figures, 1 table, supporting information https://doi.org/10.1002/aqc.3368.-- This is the peer reviewed version of the following article: Daniel Vilas, Marta Coll, Xavier Corrales, Jeroen Steenbeek, Chiara Piroddi, Antonio Calò, Antonio Di Franco, Toni Font, Paolo Guidetti, Alessandro Ligas, Josep Lloret, Giulia Prato, Rita Sahyoun, Paolo Sartor, Joachim Claudet, The effects of marine protected areas on ecosystem recovery and fisheries using a comparative modelling approach, Aquatic Conservation - Marine and Freshwater Ecosystems 30(10):1885-1901(2020), which has been published in final form at https://doi.org/10.1002/aqc.3368. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsThe overexploitation of many marine resources and ecosystems calls for the development and implementation of measures to support their recovery and conservation. The potential contributions to support fisheries and ecosystem recovery were assessed at the local level of the three multiple-use marine protected areas (MPAs) of Cerbère-Banyuls, Medes Islands, and Cap de Creus, located in the north-western Mediterranean Sea. For each MPA, a food-web model accounting for each protection level (PL) was developed: the fully protected area (FPA), the partially protected area (PPA) and the unprotected area (UPA) surrounding the MPA. Using the resulting nine food-web models, the ecosystem structure and functioning of each PL were compared and characterized, differences and similarities within and among the three MPAs were assessed, and ecosystem response to full protection was evaluated for the three MPAs. Differences in terms of ecosystem structure and functioning were found among PLs. Overall, FPAs presented the most positive effect of protection in terms of ecosystem structure and functioning, followed by PPAs. However, the effects of protection on neighbouring UPAs were hardly noticeable. Similarities between Cerbère-Banyuls and Medes Islands MPAs were observed, while Cap de Creus MPA showed the least benefits from protection overall. These results are likely to be due to similarities in the configuration of the protected areas, the levels of enforcement and compliance, and the impact of recreational and small-scale fisheries allowed in the PPAs and UPAs. This study illustrates that well-enforced Mediterranean MPAs, even when small, can yield local positive impacts on the structure and functioning of marine ecosystems that can contribute to support local fisheriesThis work was funded by EU Research Project SAFENET project (“Sustainable Fisheries in EU Mediterranean Waters through Network of MPAs.” Call for proposals MARE/2014/41, Grant Agreement n. 721708). D. Vilas benefited from a Short Term Scientific Mission by the COST Action MarCons (CA15121)With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI