Assumptions about gear efficiency and catchability influence estimates of abundance, mortality, reference points and catch potential. Despite the need to better quantify fishing effects on some target species and on many non-target species taken as bycatch, there are few gear efficiency estimates for some of the most widely deployed towed fishing gears in the northeast Atlantic. Here, we develop a method that applies generalised additive models to catch-at-length data from trawl surveys and a commercial catch and discard monitoring program in the North Sea to estimate catch-ratios. We then rescale these catch-ratios and fit relationships to estimate gear efficiency. When catches of individuals by species were too low to enable species-specific estimates, gear efficiency was estimated for species-groups. Gear efficiency (and associated uncertainty) at length was ultimately estimated for 75 species, seven species-groups and for up to six types of trawl gear per species or species-group. Results are illustrated for dab (Limanda limanda), grey gurnard (Eutrigula gurnardus) and thornback ray (Raja clavata), two common non-target species and a depleted elasmobranch. All estimates of gear efficiency and uncertainty, by length, species, species-group and gear, are made available in a supplementary data file.
Commercial fishing generally removes large and old individuals from fish stocks, reducing mean age and age diversity among spawners. It is feared that these demographic changes lead to lower and more variable recruitment to the stocks. A key proposed pathway is that juvenation and reduced size distribution causes reduced ranges in spawning period, spawning location, and egg buoyancy; this is proposed to lead to reduced spatial distribution of fish eggs and larvae, more homogeneous ambient environmental conditions within each year-class, and reduced buffering against negative environmental influences. However, few, if any, studies have confirmed a causal link from spawning stock demographic structure through egg and larval distribution to year class strength at recruitment. We here show that high mean age and size in the spawning stock of Barents Sea cod (Gadus morhua) is positively associated with high abundance and wide spatiotemporal distribution of cod eggs. We find, however, no support for the hypothesis that a wide egg distribution leads to higher recruitment or a weaker recruitment–temperature correlation. These results are based on statistical analyses of a spatially resolved data set on cod eggs covering a period (1959−1993) with large changes in biomass and demographic structure of spawners. The analyses also account for significant effects of spawning stock biomass and a liver condition index on egg abundance and distribution. Our results suggest that the buffering effect of a geographically wide distribution of eggs and larvae on fish recruitment may be insignificant compared with other impacts.
Photosynthesis fuels marine food webs, yet differences in fish catch across globally distributed marine ecosystems far exceed differences in net primary production (NPP). We consider the hypothesis that ecosystem-level variations in pelagic and benthic energy flows from phytoplankton to fish, trophic transfer efficiencies, and fishing effort can quantitatively reconcile this contrast in an energetically consistent manner. To test this hypothesis, we enlist global fish catch data that include previously neglected contributions from small-scale fisheries, a synthesis of global fishing effort, and plankton food web energy flux estimates from a prototype high-resolution global earth system model (ESM). After removing a small number of lightly fished ecosystems, stark interregional differences in fish catch per unit area can be explained (r = 0.79) with an energy-based model that (i) considers dynamic interregional differences in benthic and pelagic energy pathways connecting phytoplankton and fish, (ii) depresses trophic transfer efficiencies in the tropics and, less critically, (iii) associates elevated trophic transfer efficiencies with benthic-predominant systems. Model catch estimates are generally within a factor of 2 of values spanning two orders of magnitude. Climate change projections show that the same macroecological patterns explaining dramatic regional catch differences in the contemporary ocean amplify catch trends, producing changes that may exceed 50% in some regions by the end of the 21st century under high-emissions scenarios. Models failing to resolve these trophodynamic patterns may significantly underestimate regional fisheries catch trends and hinder adaptation to climate change.
Overfishing threatens the sustainability of coastal marine biodiversity, especially in tropical developing countries. To counter this problem, about 200 governments worldwide have committed to protecting 10%–20% of national coastal marine areas. However, associated impacts on fisheries productivity are unclear and could weaken the food security of hundreds of millions of people who depend on diverse and largely unregulated fishing activities. Here, we present a systematic theoretic analysis of the ability of reserves to rebuild fisheries under such complex conditions, and we identify maximum reserve coverages for biodiversity conservation that do not impair long-term fisheries productivity. Our analysis assumes that fishers have no viable alternative to fishing, such that total fishing effort remains constant (at best). We find that realistic reserve networks, which protect 10%–30% of fished habitats in 1–20 km wide reserves, should benefit the long-term productivity of almost any complex fishery. We discover a “rule of thumb” to safeguard against the long-term catch depletion of particular species: individual reserves should export 30% or more of locally produced larvae to adjacent fishing grounds. Specifically on coral reefs, where fishers tend to overexploit species whose dispersal distances as larvae exceed the home ranges of adults, decisions on the size of reserves needed to meet the 30% larval export rule are unlikely to compromise the protection of resident adults. Even achieving the modest Aichi Target 11 of 10% “effective protection” can then help rebuild depleted catch. However, strictly protecting 20%–30% of fished habitats is unlikely to diminish catch even if overfishing is not yet a problem while providing greater potential for biodiversity conservation and fishery rebuilding if overfishing is substantial. These findings are important because they suggest that doubling or tripling the only globally enforced marine reserve target will benefit biodiversity conservation and higher fisheries productivity where both are most urgently needed.
Management of Marine Protected Areas: A Network Perspective draws on the results of a major EU-sponsored research project related to the establishment of networks of MPAs in the Mediterranean and Black Seas that transpired from February 2011 to January 2016. Featuring contributions by leading university- and national research institute-based scientists, chapters utilize the latest research data and developments in marine conservation policy to explore issues related to ways in which networks of MPAs may amplify the effectiveness and conservation benefits of individual areas within them. Topics addressed include the broader socio-economic impacts of MPAs in the Mediterranean and Black Seas; the use of Marine Spatial Planning (MSP) to resolve conflicts between marine resource use and protection; special protection measures under the EU’s Marine Strategy Framework Directive (MSFD); ecological value assessments in the Black Sea; the Ecosystem Approach (EA) for managing marine ecosystems; MPAs along Turkey’s Black Sea coast; MPAs and offshore wind farms; and managing and monitoring MPA networks within and between the Black and Mediterranean Seas.
We assessed how establishment patterns of non-native freshwater, marine and terrestrial species into Northwest Europe (using Great Britain, France, Belgium and the Netherlands as the study countries) have changed over time, and identified the prevalent pathways and vectors of recent arrivals. Data were extracted from 33 sources on (a) presence/absence and (b) first year of observation in the wild in each country, and (c) continent(s) of origin, (d) invasion pathway(s), (e) invasion vector(s) and (f) environment(s) for 359 species, comprising all non-native Mollusca, Osteichthyes (bony fish), Anseriformes (wildfowl) and Mammalia, and non-native invasive Angiospermae present in the area. Molluscs, fish and wildfowl, particularly those originating from South America, arrived more recently into Northwest Europe than other groups, particularly mammals, invasive plants and species originating from North America. Non-deliberate introductions, those of aquatic species and those from elsewhere in Europe and/or Asia increased strongly in importance after the year 2000 and were responsible for 69, 83 and 89 % of new introductions between 2001 and 2015, respectively. Non-deliberate introductions and those from Asia and North America contributed significantly more to introductions of invasive species in comparison to other non-native species. From the 1960s, ornamental trade has increased in importance relative to other vectors and was responsible for all deliberate introductions of study groups since 2001. Non-deliberate introductions of freshwater and marine species originating from Southeast Europe and Asia represent an increasingly important ecological and economic threat to Northwest Europe. Invertebrates such as molluscs may be particularly dangerous due to their small size and difficulties in detection. Prevention of future invasions in this respect will require intensive screening of stowaways on boats and raising of public awareness.
With the transition to the commercial-scale exploitation of deep seabed minerals, the International Seabed Authority’s obligation to protect the marine environment is being tested. In The International Seabed Authority and the Precautionary Principle, Aline L. Jaeckel provides the first in-depth analysis of the Authority’s work in regulating and managing deep seabed minerals.
This book examines whether and to what extent the Authority is implementing the precautionary principle in practice. This includes the development of adequate environmental protection standards as well as procedural safeguards and decision-making processes that facilitate risk assessment and risk management. In doing so, the author offers an insightful example of how the precautionary principle can be translated into a practical management tool.
Effectively addressing climate change requires significant changes in individual and collective human behavior and decision-making. Yet, in light of the increasing politicization of (climate) science, and the attempts of vested-interest groups to undermine the scientific consensus on climate change through organized “disinformation campaigns,” identifying ways to effectively engage with the public about the issue across the political spectrum has proven difficult. A growing body of research suggests that one promising way to counteract the politicization of science is to convey the high level of normative agreement (“consensus”) among experts about the reality of human-caused climate change. Yet, much prior research examining public opinion dynamics in the context of climate change has done so under conditions with limited external validity. Moreover, no research to date has examined how to protect the public from the spread of influential misinformation about climate change. The current research bridges this divide by exploring how people evaluate and process consensus cues in a polarized information environment. Furthermore, evidence is provided that it is possible to pre-emptively protect (“inoculate”) public attitudes about climate change against real-world misinformation.
National Biodiversity Strategy and Action Plans (NBSAPs) are key instruments for defining priorities and modalities for effective, ef cient and equitable biodiversity management at the national level and across key sectors. As such, they provide important opportunities to recognize and integrate women’s empowerment and gender equality considerations.
Out of the 254 total NBSAP reports from 174 countries (presented from 1993 to 2016), 143 reports (56% of total documents) from 107 countries (61% of total countries examined) contain at least one gender and/or women keyword.
With respect to how women and women’s participation are characterized in NBSAPs, the most countries (37% of the 174 Parties included in this analysis) indicate inclusion of women as stakeholders; 27% include reference to women as beneficiaries; 17% refer to women as vulnerable; and the fewest, 4% (seven countries) characterize women as agents of change.
Gender considerations are integrated in various ways and across multiple sections of NBSAPs. For example, 14% of countries include women’s empowerment and/or gender equality as a guiding principle. Approximately one-quarter (24%) of most recent NBSAPs include at least one specific activity geared towards women or otherwise proactively including gender considerations, e.g., to address gender gaps.
Echoing common themes across decades of CBD decisions, 26 countries (15%) reference women as keepers of traditional ecological knowledge (TEK) in relation to their roles as farmers, fishers, and elders of indigenous communities in at least one of their NBSAPs, while 41 countries (24%) reference women as stewards of the environment in at least one NBSAP.
Recent coastal planning measures in south-east Portugal (Algarve), where offshore aquaculture developments were set up in fishing areas aiming to maximize expected utility of seafood production activities, raised some discontentment. Public policies created to safeguard offshore aquaculture (OSA) producers and limit small-scale fishing (SSF) activities must be adjusted accordingly in order to maximize income and keep discontentment at a minimum. We collected primary data from stakeholders, fishers (n = 18) and offshore aquaculture operators (n = 3) through participatory workshops and interviews by eliciting problematic issues derived from the offshore area creation and their relative relevance. We used these data to populate conditional probability tables and construct a related influence diagram (Bayesian belief networks) to model the affected system. We selected nine scenarios based on navigability and aquaculture area size with the aim of finding the best expected utility combinations for the OSA – SSF system. The inferred results show that maximizing employment and keep pollution at low levels were the most influential factors to keep the system at a satisfactory level. The best decision was not to enlarge the aquaculture area, but to condition the access to other operational stakeholders, namely SSF operators from nearby areas. The overall results of the Bayesian belief network can be used to recommend coastal planners and decision-makers to deal with the interaction between OSA and SSF activities.