It is well-established that phytoplankton growth can be limited by the vanishingly low concentrations of dissolved iron found in large areas of the open ocean. However, the availability of iron is not typically considered an important factor in the ecology of marine animals, including fish. Here, we compile observations to show that the iron contents of lower trophic level organisms in iron-limited regions can be an order of magnitude less than the iron contents of most fish. Although this shortfall could theoretically be overcome if iron assimilation rates were very high in fish, observations suggest this is not the case, consistent with the high recommended iron contents for mariculture feed. In addition, we highlight two occurrences among fish living in iron-poor regions that would conceivably be beneficial given iron scarcity: the absence of hemoglobin in Antarctic icefish, and the anadromous life history of salmon. Based on these multiple lines of evidence, we suggest that the iron content of lower trophic level organisms can be insufficient to support many fish species throughout their life cycles in iron-poor oceanic regions. We then use a global satellite-based estimate of fishing effort to show that relatively little fishing activity occurs in high nitrate low chlorophyll (HNLC) regions, the most readily identified iron-poor domains of the ocean, particularly when compared to satellite-based estimates of primary production and the observed mesozooplankton biomass in those waters. The low fishing effort is consistent with a low abundance of epipelagic fish in iron-limited regions, though other factors are likely to contribute as well. Our results imply that the importance of iron nutrition extends well beyond plankton and plays a role in the ecology of large marine animals.
Fisheries and Fisheries Management
African maritime countries take the majority of their animal protein from fish. Bound with tradition and a promise of food and other values, African fisheries also provide a source of livelihood for over 35 million coastal fishers. Yet, as in many other regions of the world, the fishing sector is plagued with policy failures, and illegal activities. This paper summarizes the key points in the evolution of African fisheries in terms of exploitation, policy, and maritime security trends. It addresses how access to fishing by the small-scale sector is increasingly hindered by the increasing power and scope of an industrial fleet often involved in Illegal, Unreported, and Unregulated (IUU) fishing. It also discusses the impacts of ineffective enforcement against overexploitation and illegal fishing, piracy, human smuggling and climate-change risks for coastal communities, as well as policy measures and initiatives to reverse the existing trends.
In 2015–2016, a gear-specific assessment of the Gizo, Solomon Islands, commercial inshore fishery was conducted to assist management decision making. The survey identified at least 260 species and 25 families among over 14,000 individual catch- and gear-specific fish photos taken using a digital image capture system. Seventy-nine fishers provided 175 catches during surveys and more than 1,600 fisher and vendor interviews were conducted. More than 75% of all individual fish sampled belonged to nine families that included groupers (Epinephelidae) with 29 species and snappers (Lutjanidae) with 28 species. Groupers, snappers and emperors (Lethrinidae) dominated line-caught fish, while speared catch was composed primarily of parrotfish (Scaridae) and surgeonfish and unicornfish (Acanthuridae). Catch-per-unit effort (CPUE) was 3.9 ± 0.1 kg hr−1 fisher−1 overall, with the highest CPUE for line fishing at 4.5 ± 1.6 kg hr−1 and lowest CPUE for nighttime spearfishing (2.1 ± 0.4 kg hr−1). Gear-specific size distributions and species targeted varied widely, with juveniles dominating most catches for speared fish. Between line-caught and speared catch, only two species were common within the top 25 species. At the time of the study there were no enacted national regulations related to finfish in the inshore fishery in Solomon Islands. Community-based management approaches have been endorsed by government and non-government entities in Solomon Islands, however a greater level of community engagement and voluntary fisher compliance is needed in concert with government enforcement to control potential overfishing, particularly nighttime spearfishing. Ongoing support for precautionary, adaptive management is a recommended course of action to limit the potential for overfishing in Gizo and other coastal areas of high human population density that rely heavily on marine resources.
This paper estimates the price changes in global bluefin tuna (BFT) markets in response to shifts in regional and global landings to evaluate the conservation and economic incentives from changes in the Total Allowable Catch (TAC) managed by all three Regional Fisheries Management Organizations. A fisherman’s income, and thus the financial incentive to accept management measures controlling catch levels, depends in part on how responsive price is to overall catch. Individual fisherman, with their own best interest in mind, used to wish to increase their individual landings and create an incentive to ask to increase the TAC for the industry, without realizing the possible revenue loss due to the resulting falling prices. To protect the value of all stakeholders’ property rights, a consensus to avoid abruptly raising the TAC, without first considering the potential loss due to market response, is needed. Alternatively, if revenue increases with lower TAC, a positive economic incentive for conservation is created if price increasing proportionately more than the lower supply, with harvest profits boosted by lower costs of production. To capture the complexity of substituting across various sources of supply and product form, a general synthetic inverse demand system is estimated to identify the impact of overall landings on BFT prices. This system estimates price flexibilities of both fresh and frozen longline-caught sashimi-grade tunas (Pacific, Atlantic and southern bluefins, and bigeye) at the Tokyo Center Market in Japan, including the Tsukiji Market, the world’s largest fish auction market that served as the single global price leader for BFT. The resulting estimation shows that own-quantity price flexibilities of every type of fresh and frozen BFTs are less than unity and inflexible in their own consumption. This creates poor individual producer incentives for fishermen to reduce wild or farmed BFT supply, as there is a chance to increase their own revenue, under the unlikely condition that the total supply is fixed. However, by observing the rapid increases in the TAC of Eastern Atlantic bluefin tuna (EABFT) in the coming years, suppliers may not be better off as price will drop proportionally faster and total revenue if the estimated scale flexibility is greater than one. Based on the estimated scale flexibility of frozen BFT, which is slightly less than unity, the frozen subsector of EABFT suppliers is the only winner under the supply increases. Suppliers of frozen BFT in other regions, fresh BFT (in the Atlantic and elsewhere), and southern BFT and bigeye tuna will all be harmed through lower revenue by the supply increases. Additionally, while total revenue might stay the same for frozen BFT suppliers, fishermen will potentially receive lower profits due to higher operating costs associated with increased landings when the supply of EABFT increases. Given the number of sectors that ultimately lose financially in the short term and given the ecological (and production) risks accompanying an abrupt increase in fishing pressure in the long term, the global economic losses resulting from an increase in the allowable catch of Atlantic bluefin tuna will outweigh any potential increases to revenue.
Managing fisheries to meet social, economic and ecological objectives is a fundamental problem encountered in fisheries management worldwide. In Australia, fisheries management involves a complex set of national and sub-national policy arrangements, including those designed to deliver against ecologically sustainable development (ESD) objectives. The complex policy framework makes ensuring policy coherence and avoiding unintended consequences difficult, particularly where potential trade-offs are not made explicit. Coherence, or potential policy weakness, of Australian fisheries management in relation to ESD objectives was examined in a subset of Australian wild capture fisheries, at national and jurisdictional scales. Coherent policy frameworks with ESD objectives were found to be more likely at the legislative-level across jurisdictions (horizontal coherence), than other levels of implementation. Many fisheries had problems demonstrating coherence between legislation and management plans due to lack of inclusion of ESD policy themes at management and operational levels. Case studies revealed substantial variation in the likelihood for horizontal and vertical coherence between fisheries policy frameworks managing the same species. The lack of explicit ESD objectives observed in many Australian fisheries suggests a high likelihood of incoherence in fisheries management, or alternatively that managers may be informally persuing higher levels of policy coordination and coherence than can be detected. Lack of detectability of coherence is problematic for demonstrating accountability and transparency in decision-making and public policy. Furthermore, use of discretion by managers when developing management plans, in order to overcome policy weakness, may lead to drifts in individual management direction within a jurisdiction.
Marine Protected Areas (MPAs) have been used to protect species in need of conservation and as a fisheries management tool. It has been suggested MPAs can benefit mobile stocks by protecting spawning grounds whilst also allowing yields to be maintained as mature fish move out of the protected areas. However, the robustness of this claim in mixed species fisheries has yet to be established. We use a simulation model to explore the efficacy of spatial closures and effort regulation when other forms of fishery control (e.g., Total Allowable Catches) are absent or non-enforced as ways of addressing management objectives that are difficult to reconcile due to the contrasting life-histories of a target and a bycatch, conservation species in a two-species fishery. The mobility of each stock in such a fishery affects the benefits conferred by an MPA. The differing management objectives of the two species can be partially met by effort regulations or closures when the species exhibit similar mobility. However, a more mobile conservation species prevents both sets of aims being met by either management tool. We use simulations to explore how spatial closures and effort regulation can be used to seek compromise between stakeholders when the mobility of one stock prevents conflicting management objectives to be fully met. Our results demonstrate that stock mobility is a key factor in considering whether an MPA can meet conflicting aims in a multispecies fishery compromised of stocks with differing life histories and mobilities.
Migration is a widespread but highly diverse component of many animal life histories. Fish migrate throughout the world's oceans, within lakes and rivers, and between the two realms, transporting matter, energy, and other species (e.g., microbes) across boundaries. Migration is therefore a process responsible for myriad ecosystem services. Many human populations depend on the presence of predictable migrations of fish for their subsistence and livelihoods. Although much research has focused on fish migration, many questions remain in our rapidly changing world. We assembled a diverse team of fundamental and applied scientists who study fish migrations in marine and freshwater environments to identify pressing unanswered questions. Our exercise revealed questions within themes related to understanding the migrating individual's internal state, navigational mechanisms, locomotor capabilities, external drivers of migration, the threats confronting migratory fish including climate change, and the role of migration. In addition, we identified key requirements for aquatic animal management, restoration, policy, and governance. Lessons revealed included the difficulties in generalizing among species and populations, and in understanding the levels of connectivity facilitated by migrating fishes. We conclude by identifying priority research needed for assuring a sustainable future for migratory fishes.
As global fisheries management shifts towards ecosystem-based management, responsible organizations and governments must also address the socio-economic impacts of this shift. This study evaluates potential impacts of such management shift with a case study of Pulley Ridge (PR), an ecologically rich area in the Gulf of Mexico, on fishermen and economies of Florida's Gulf Coast. We developed an input-output model to estimate direct, backward-linkage, forward-linkage, and induced consumption effects of various management scenarios on the region's economy. We also solicited input on the proposed management changes from Florida saltwater fishing license holders using an online survey. Although gear restrictions may affect harvest of the region's two most lucrative fish types, snappers and groupers, the proposed changes would impact only a small fraction of the fishing industry and the regional economy. Results suggest economic impacts to affected counties and the overall Gulf Coast fishery from management changes would be limited, i.e., less than 3% reductions in income, taxes and employment. Nonetheless, almost 90% of survey respondents indicated the proposed management changes would affect their business either “Significantly” or “Very Significantly”. Results suggest developing broad based support for changes affecting the commercial fishing sector may require stakeholder negotiation along with convincing evidence that the proposed changes will improve regional fishery production in the near term.
Small-scale fisheries are facing increasing pressures due to overexploitation of resources, resulting in decreased fish stocks, biodiversity loss, and degradation of marine ecosystems. The unregulated open access conditions of these systems are considered a main driver of this context, leading to increasing calls for fisheries reform over the past decade. Belize is no exception, recently introducing a rights-based fisheries territorial system (Managed Access Program – MAP) aimed at incentivizing fisher ownership and stewardship of regions to promote sustainability. The implementation of managed access brings with it an interaction of actors and issues at the local and regional scale that raises questions about the feasibility and potential success of the program. In this paper, using a combination of literature review and semi-structured interviews with 54 fishers and 25 policymakers across Belize's fisheries sector, we provide a policy analysis of the MAP and review initial responses. We found the new system to be primarily a re-packaging of traditional fishing areas with unenforced regulations. Responses from stakeholders were varied around the implementation of the MAP, with the majority of references being negative in tone. While the introduction of MAP in Belize seeks to provide solutions to Belize's fisheries sector, questions remain around the ability of the MAP to meet its objectives.
Effective ocean management and the conservation of highly migratory species depend on resolving the overlap between animal movements and distributions, and fishing effort. However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space-use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively), and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas). Our results demonstrate an urgent need for conservation and management measures at high-seas hotspots of shark space use, and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real-time, dynamic management.