Scientific monitoring is a fundamental basis of scientific advice. Among others, monitoring aims at contributing towards understanding the influence of anthropogenic use (e.g. fisheries), the health ...of a stock and individuum and effectiveness of management and conservation measures (e.g. MPAs). Monitoring of demersal and benthic fish communities is often based on invasive methods like bottom trawling, however in some cases less invasive methods might be available. The need for developing alternative and less invasive monitoring methods is supported by an increasing number of Marine Protected Areas and Windfarms where traditional methods such as trawls cannot be deployed due to conservational or technical and safety reasons. To support the development of new monitoring concepts, we conducted a literature review to identify limits and opportunities of methods that are already available. Furthermore, we present a fit-for purpose guide that can help identifying the appropriate method for individual purposes. We defined eight different methods which were analyzed using four different criteria and listed their advantages and disadvantages. We further apply this guide to monitoring in Marine Protected Areas in the Baltic Sea as a case study, indicating that besides traditional bottom trawling, alternative and less invasive methods could be sufficient for specific research purposes. We therefore, encourage scientists and managers to consider alternative data collection methods to minimize environmental impact of scientific sampling. However, our results also indicate that most of the methods still need further refinement especially regarding sampling design, standardization of methods and comparability with established survey methods.
The lesser flying squid (Todaropsis eblanae) and the shortfin squid (Illex coindetii) are two abundant ommastrephids of the northeast Atlantic. Spawning ground existence was inferred from the ...captures of mature, mated females in summer 2016–2019 and their occurrences were compared with respective oceanographic data from international surveys to gain insight into environmental predictors of their presence throughout the North Sea. Spawning T. eblanae were found in relatively cooler and more saline waters (6–8°C, 34.2–35.1 psu) in the northern North Sea linked to the Fair Isle Current and East Shetland Atlantic Inflow, whilst spawning I. coindetii occurred across the entire North Sea (mostly at 9–10.5°C, 34.1–34.8 psu). We hypothesize that a combination of water salinity and water temperature are key factors in the spatiotemporal distribution of spawning ommastrephid squids as they define water density that is crucial for pelagic egg mass to attain neutral buoyancy.
We examined small-scale distribution and feeding ecology of a non-native fish species, round goby (
Neogobius melanostomus
(Pallas, 1814)), in different habitats of a coastal lagoon situated in the ...south-western Baltic Sea. First observations of round goby in this lagoon were reported in 2011, 3 years before the current study was conducted, and information on this species’ basic ecology in different habitats is limited. We found that mainly juvenile round gobies are non-randomly distributed between habitats and that abundances potentially correlate positively with vegetation density and thus structural complexity of the environment. Abundances were highest in shallower, more densely vegetated habitats indicating that these areas might act as a refuge for small round gobies by possibly offering decreased predation risk and better feeding resources. Round goby diet composition was distinct for several length classes suggesting an ontogenetic diet shift concerning crustacean prey taxa between small (≤ 50 mm total length, feeding mainly on zooplankton) and medium individuals (51–100 mm, feeding mainly on benthic crustaceans) and another diet shift of increasing molluscivory with increasing body size across all length classes. Differences in round goby diet between habitats within the smallest length class might potentially be related to prey availability in the environment, which would point to an opportunistic feeding strategy. Here, we offer new insights into the basic ecology of round goby in littoral habitats, providing a better understanding of the ecological role of this invasive species in its non-native range, which might help to assess potential consequences for native fauna and ecosystems.
The study of marine food web models has increased during the last years, but input data of important groups such as cephalopods are missing sometimes which restricts the quality of the model results. ...Cephalopods feed on a variety of preys, ranging from small crustaceans to large commercially important fish species. In turn, they are taken by larger invertebrates, fish, cephalopods, marine mammals and seabirds, which emphasizes their important role in various marine food webs. Our study presents stomach content analyses of various cephalopod species from the North Sea and describes their general feeding trends. The results further support the inclusion of cephalopods as predators into food web models to increase our knowledge of the North Sea ecosystem and to improve its management. Our data in combination with observed increasing biomasses of North Sea cephalopods suggest that the impact of cephalopods in the North Sea food web has increased and that large-sized cephalopods have become more important as predators for commercially exploited fish species during recent years.
The veined squid, Loligo forbesii Steenstrup, 1856, occurs at the European Shelf areas including the Azores and represents a valuable resource for the European commercial fishery in the North East ...Atlantic. However, very little is known about its population structure and phylogeography. This lack of knowledge also impedes the development of sustainable fishery management for this species. The present study combined the use of two types of markers that retrieve patterns of gene flow in different time spans; the analysis of 16 nuclear microsatellites and sequencing of the mitochondrial cytochrome oxidase subunit I (COI). Whereas the high mutation rate of microsatellites allows the description of recent patterns of connectivity in species, the lower mutation rate of COI provides phylogeographic patterns on a longer timescale. A total of 347 individuals of L. forbesii were investigated from nearly the entire distribution range of the species, including the North East Atlantic Shelf, the Azores and the Mediterranean. Individuals from the Western and Eastern Mediterranean Sea have never been included in a genetic study before. We were able to analyse COI sequences from all 12 sampling areas and define three clades of L. forbesii. Due to our large sampling area, we are presenting 13 COI-haplotypes that were previously unknown. The microsatellite analysis does not include the Azores but three main clades could be identified at the remaining 11 sampling sites. Low F
values indicate gene flow over large geographical distances. However, the genetically significant differences and an additional slight grouping in the microsatellite structure reveal that geographical barriers seem to influence the population structure and reduce gene flow. Furthermore, both markers provide strong evidence that the observed phylogeographic pattern reflects the geographical history of the Azores and the Mediterranean Sea.
Marine protected areas (MPAs) are designated parts of the ocean that restrict human activities to a certain degree. MPAs are established around the world using a wide range of legislative instruments ...and thus come in a variety of forms and shapes. Despite being regarded as the “cornerstone” of global marine conservation efforts, they currently cover less than 10% of the ocean surface. Individual MPAs aim to achieve goals ranging from the protection of specific habitats or species to sustaining certain commercial activities, such as fishing. By default, the establishment of MPAs intertwines social, ecological and economic considerations. Yet, the emphasis put on each of these domains can vary substantially when setting on-the-ground objectives, frequently creating conflict among stakeholders. In this manuscript, we first discuss current international conservation targets as well as potential future goals and delve into the question of how to assess the effectiveness of MPAs. Subsequently, we discuss the ambivalent role of this widely applied management tool at the crossroads between biodiversity conservation and fisheries management. Placing MPAs in a social-ecological framework, we call for clear and measurable goals to evaluate MPAs from an interdisciplinary perspective. Finally, we present the Baltic Sea, with its high degree of anthropogenic impact, long fishing history and comparatively extensive MPA coverage, as an interesting case study to investigate the role of MPAs in promoting a sustainable management of the ocean.
Bottom trawling is one of the main pressures on benthic ecosystems, directly impacting the targeted species and physically disturbing the seabed and the benthic invertebrate communities, in turn ...indirectly impacting benthivorous fish and the entire benthic food web structure and functioning. To predict the cascading effect of bottom trawling on benthic and demersal fish communities, it is crucial to understand the trophic interactions between benthic and demersal fish and benthic invertebrates. Here, we assessed the diet of benthic and demersal fish and the structure and functioning of the benthic food web in two areas in the German Baltic Sea, the Fehmarnbelt and the Odra Bank. The Fehmarnbelt benthic invertebrate community is characterized by a high number of species and biomass, contrary to the one on the Odra Bank which is species poor with high individual abundance but low biomass. We used mixing models based on stable isotopes of carbon and nitrogen combined with stomach content analyses to estimate the fish diet at both sites, and we used community-wide trophic indices, derived from stable isotopes to compare the structure and functioning of the fish benthic food webs. We show that fish in the Fehmarnbelt can chose preferential prey items, resulting in higher trophic diversity, contrary to fish on the Odra Bank, which feed on all available prey species, resulting in higher trophic redundancy. We found that the generalist behavior of fish on the Odra Bank is likely the result of scarcity in prey items, the benthic invertebrate community being species poor with high abundance of small individuals. We demonstrate that the differences in structure and functioning of the benthic fish food web between the two sites was mainly driven by differences in the characteristics of the benthic prey communities.
In the marine sciences an increasing number of studies on environmental changes, their causes, and environmental assessments emerged in recent years. Often authors use non-uniform and inconsistent ...definitions of key terms like driver, threats, pressures etc. Although all of these studies clearly define causal dependencies between the interacting socio-economic and environmental systems in an understandable way, still an overall imprecise wording could induce misunderstanding at higher policy levels when it comes to integrated ecosystems assessments. Therefore we recommend using unified definitions for a better communication between science and management within national, regional and international environmental policies, for example the European Marine Strategy Framework Directive (MSFD). With this article we provide definitions compatible with the driver-pressure-state-impact-response (DPSIR) approach. Although most examples are MSFD related and thus have a marine focus the definitions are intended to be equally applicable for other systems and are usable world-wide. We suggest sticking to these definitions for an easy and simplified knowledge transfer from science to management, since DPSIR model is already accepted as a helpful tool for structuring and communicating ecosystem analyses.
•Authors use inconsistent definitions of key terms like driver and pressure.•An imprecise wording could induce misunderstanding between science and policy.•We provide definitions of key terms compatible with the DPSIR approach.
Abstract
Survey-based abundance indices (catch per unit effort, cpue) and harvest ratios (HRs) are usable proxies for spawning-stock biomass and fishing mortality (F). Here, we present an easy ...approach to calculate secondary indicators based on a public dataset. However, the performance of different cpue/HR indicator metrics varied between stocks, and, therefore, the adequate metrics for secondary indicators should be chosen for each stock after careful analysis by experts.
This experimental field study provides first insights into the impact of a widely spread non-native fish species, round goby Neogobius melanostomus (Pallas 1814), on the diversity of native epifaunal ...macroinvertebrate communities in the Baltic Sea. A cage experiment was conducted in a macrophyte habitat in the Åland islands located in the northern Baltic Sea. Round gobies (13.5 ± 0.8 cm) affected macroinvertebrate biodiversity from a taxonomic and a trait-based point of view. Specifically, round goby decreased overall abundance, biomass and taxon richness of epifaunal invertebrates. Additionally, taxonomic and trait-based composition were affected, as the gobies reduced abundances of common bivalve (Cerastoderma spp. and Mytilus sp.) and gastropod species (Hydrobia spp.), and thereby modified the relative trait composition of the invertebrate assemblages. Round gobies consumed mainly larger epifaunal individuals leading to an overall decrease in invertebrate body size. Such alterations in taxonomic and trait-based diversity and composition of invertebrate communities through round goby predation may have implications for native fish species and other trophic levels in the respective food webs through food competition and trophic cascades. Round gobies might therefore affect ecosystem processes in invaded areas, and thus influence ecosystem functioning and services.
Display omitted
•A cage experiment tested round goby impact on invertebrates in the Baltic Sea.•Impact on taxonomic and trait-based invertebrate biodiversity was assessed.•Gobies decreased abundance, biomass and taxon richness of native invertebrates.•Abundances of common bivalve and gastropod species were lower in round goby presence.•Round goby affected trait composition and decreased overall invertebrate body size.
PDF
