The future of food from the sea.

Global food demand is rising, and serious questions remain about whether supply can increase sustainably1. Land-based expansion is possible but may exacerbate climate change and biodiversity loss, and compromise the delivery of other ecosystem services2-6. As food from the sea represents only 17% of the current production of edible meat, we ask how much food we can expect the ocean to sustainably produce by 2050. Here we examine the main food-producing sectors in the ocean-wild fisheries, finfish mariculture and bivalve mariculture-to estimate 'sustainable supply curves' that account for ecological, economic, regulatory and technological constraints. We overlay these supply curves with demand scenarios to estimate future seafood production. We find that under our estimated demand shifts and supply scenarios (which account for policy reform and technology improvements), edible food from the sea could increase by 21-44 million tonnes by 2050, a 36-74% increase compared to current yields. This represents 12-25% of the estimated increase in all meat needed to feed 9.8 billion people by 2050. Increases in all three sectors are likely, but are most pronounced for mariculture. Whether these production potentials are realized sustainably will depend on factors such as policy reforms, technological innovation and the extent of future shifts in demand.

Climate change and overfishing increase neurotoxicant in marine predators.

More than three billion people rely on seafood for nutrition. However, fish are the predominant source of human exposure to methylmercury (MeHg), a potent neurotoxic substance. In the United States, 82% of population-wide exposure to MeHg is from the consumption of marine seafood and almost 40% is from fresh and canned tuna alone1. Around 80% of the inorganic mercury (Hg) that is emitted to the atmosphere from natural and human sources is deposited in the ocean2, where some is converted by microorganisms to MeHg. In predatory fish, environmental MeHg concentrations are amplified by a million times or more. Human exposure to MeHg has been associated with long-term neurocognitive deficits in children that persist into adulthood, with global costs to society that exceed US$20 billion3. The first global treaty on reductions in anthropogenic Hg emissions (the Minamata Convention on Mercury) entered into force in 2017. However, effects of ongoing changes in marine ecosystems on bioaccumulation of MeHg in marine predators that are frequently consumed by humans (for example, tuna, cod and swordfish) have not been considered when setting global policy targets. Here we use more than 30 years of data and ecosystem modelling to show that MeHg concentrations in Atlantic cod (Gadus morhua) increased by up to 23% between the 1970s and 2000s as a result of dietary shifts initiated by overfishing. Our model also predicts an estimated 56% increase in tissue MeHg concentrations in Atlantic bluefin tuna (Thunnus thynnus) due to increases in seawater temperature between a low point in 1969 and recent peak levels-which is consistent with 2017 observations. This estimated increase in tissue MeHg exceeds the modelled 22% reduction that was achieved in the late 1990s and 2000s as a result of decreased seawater MeHg concentrations. The recently reported plateau in global anthropogenic Hg emissions4 suggests that ocean warming and fisheries management programmes will be major drivers of future MeHg concentrations in marine predators.

Supply and demand drive a critical transition to dysfunctional fisheries.

There is growing awareness of the need for fishery management policies that are robust to changing environmental, social, and economic pressures. Here we use conventional bioeconomic theory to demonstrate that inherent biological constraints combined with nonlinear supply-demand relationships can generate threshold effects due to harvesting. As a result, increases in overall demand due to human population growth or improvement in real income would be expected to induce critical transitions from high-yield/low-price fisheries to low-yield/high-price fisheries, generating severe strains on social and economic systems as well as compromising resource conservation goals. As a proof of concept, we show that key predictions of the critical transition hypothesis are borne out in oceanic fisheries (cod and pollock) that have experienced substantial increase in fishing pressure over the past 60 y. A hump-shaped relationship between price and historical harvest returns, well demonstrated in these empirical examples, is particularly diagnostic of fishery degradation. Fortunately, the same heuristic can also be used to identify reliable targets for fishery restoration yielding optimal bioeconomic returns while safely conserving resource abundance.

Optimization of fishing for stock enhancement of Rutilis rutilus and Scardinius erythropththalmus in forage fish-deficient Tunisian reservoirs.

Twenty specially designed fishing nets were used to catch broodstock of the forage fish roach and rudd (Rutilus rutilus and Scardinius erythrophthalmus). The monofilament gill nets were of different mesh sizes (18, 22, 24, and 26 mm) but of identical dimensions (4 × 50 m). The fish, caught in Sidi Salem reservoir in 2014, amounted to a total of 8901 roach and rudd caught at 41 different times; 3335 broodstock forage fish were transferred to 11 forage fish-deficient Tunisian reservoirs. The best yields (0.464 fish/m2) were obtained with fishing gear fitted with 18-mm mesh size; however, fish mortality with this net was very high, exceeding 83.36%. The greatest efficiency was obtained using nets of 22- and 24-mm mesh with a number of fish per unit effort (NPUE) of 0.181 and 0.173 fish/m2, and a mortality of 54.34 and 53.85%, respectively. Gill nets of 26-mm mesh size were inappropriate (lowest yield 0.129 fish/m2). Length of rudd and roach at first maturity and Gonadosomatic index (GSI) were measured, indicating that all transferred fish were mature. Transfer techniques were improved by holding the captured fish for 5 days before release into the host reservoir.

Short-term impacts and value of a periodic no take zone (NTZ) in a community-managed small-scale lobster fishery, Madagascar.

The small-scale lobster fisheries of Madagascar's impoverished southeast coast account for the majority of national catch and export, making a significant contribution to the regional economy. Data suggests catches have declined, likely due to over-exploitation. In response, the community of Sainte Luce has established a locally managed marine area (LMMA) to manage their lobster fishery, including a 13 km2 periodic no take zone (NTZ). Participatory monitoring data were used to assess compliance, identify changes in catch per unit effort (CPUE) associated with the NTZ and consider the short-term value of the NTZ. Compliance is low for measures dictated by national legislation (minimum landing size (MLS), national closed season, prohibition on landing berried females), but may be higher for those designed by the community (NTZ). Upon NTZ opening in July 2015, an estimated 435% increase in catch was observed compared with the mean for the preceding five months, a product of increased effort and significantly higher CPUE. Zero Altered Negative Binomial modelling showed CPUE was significantly higher during the NTZ opening in 2015 and in 2016 when the opening period had been moved. Whilst it is unlikely that tangible ecological benefits have accrued from NTZ operation, there have been important socio-economic effects. Specifically, there was a 33% increase in the price fishers received, a significant effect at the bottom of the value chain. Temporary increases in catch and income acted as a catalyst, engaging neighbouring communities in fishery management, resulting in two additional NTZs. Attention is drawn to the fact that current national legislation may be sub-optimal and should be reviewed. Successful management of the regional fishery will require the state and industry to support communities in adopting community-based management. The NTZ measure considered here may be an effective tool to achieve this.

Viability and Management Targets of Mediterranean Demersal Fisheries: The Case of the Aegean Sea.

Management of the Mediterranean demersal stocks has proven challenging mainly due to the multi-species character of the fisheries. In the present work, we focus on the multi-species demersal fisheries of the Aegean Sea (eastern Mediterranean) aiming to study the effects of different management measures on the main commercial stocks, as well as to explore the economic viability of the fisheries depending upon these resources, by means of simulated projections. Utilizing the limited available data, our results demonstrated that, under the current exploitation pattern, the economic viability of the fleets is threatened, particularly if fuel prices increase. Additionally, the biological targets set for the most exploited species, such as hake, will not be met under the current management regime. The projections also showed that the only management scenario under which both resource sustainability and economic viability of the fisheries are ensured is the decrease of fleet capacity in terms of vessel numbers. In this case, however, measures to support the fisheries-dependent communities need to be implemented to prevent the collapse of local economies due to employment decrease. Scenarios assuming selectivity improvements would be also beneficial for the stocks but they showed low economic performance and their application would threaten the viability of the fleets, particularly that of the trawlers.

Time Preferences and Natural Resource Extraction Behavior: An Experimental Study from Artisanal Fisheries in Zanzibar.

Natural resource users face a trade-off between present and future consumption. Using harmful methods or extracting unsustainably, lowers future consumption. Therefore, it is reasonable to posit that people with higher time preferences extract more as compared to people with lower time preferences. The present study combines experimental methods and questionnaire data in order to understand the relationship between individual time preferences and fishers' extraction behavior. We elicit individual time preferences using an incentivized experiment, linking the resulting time preference measures to extraction data from a questionnaire, as well as data collected from a framed Common Pool Resource (CPR) experiment. Both the experiments and questionnaire were conducted with artisanal fishers in Zanzibar. Our findings suggest that the relationship between time preferences and CPR extraction is not as straightforward as predicted by classical economic theory. In contrast to earlier studies, we find that fishers' time preferences are negatively correlated to their extraction rates. Our surprising findings can partly be explained by the fact that higher time preferences are associated with lower investment in extraction capability (the disinvestment effect of time preferences), and by fishers´ cognitive abilities.

Impact of High Seas Closure on Food Security in Low Income Fish Dependent Countries.

We investigate how high seas closure will affect the availability of commonly consumed food fish in 46 fish reliant, and/or low income countries. Domestic consumption of straddling fish species (fish that would be affected by high seas closure) occurred in 54% of the assessed countries. The majority (70%) of countries were projected to experience net catch gains following high seas closure. However, countries with projected catch gains and that also consumed the straddling fish species domestically made up only 37% of the assessed countries. In contrast, much fewer countries (25%) were projected to incur net losses from high seas closure, and of these, straddling species were used domestically in less than half (45%) of the countries. Our findings suggest that, given the current consumption patterns of straddling species, high seas closure may only directly benefit the supply of domestically consumed food fish in a small number of fish reliant and/or low income countries. In particular, it may not have a substantial impact on improving domestic fish supply in countries with the greatest need for improved access to affordable fish, as only one third of this group used straddling fish species domestically. Also, food security in countries with projected net catch gains but where straddling fish species are not consumed domestically may still benefit indirectly via economic activities arising from the increased availability of non-domestically consumed straddling fish species following high seas closure. Consequently, this study suggests that high seas closure can potentially improve marine resource sustainability as well as contribute to human well-being in some of the poorest and most fish dependent countries worldwide. However, caution is required because high seas closure may also negatively affect fish availability in countries that are already impoverished and fish insecure.

Fishers' resource mapping and goliath grouper Epinephelus itajara (Serranidae) conservation in Brazil

Goliath grouper (Epinephelus itajara) aggregations and relative abundances were described and mapped through the use of fishermen's local ecological knowledge in Babitonga Bay in southern Brazil. Six well-experienced informants were asked to individually provide information about goliath grouper abundance and distribution, drawn over a satellite image of the study area, which was later overlaid and gathered into a final map. According to our informants, the goliath grouper occurs along a broad salinity and depth range, from shallow estuarine areas (less than 5 m deep) with high freshwater input (smaller individuals, up to 150 kg) to coastal marine-dominated environments (at least 35 m deep); (larger individuals more common, frequently reaching more than 300 kg). Fishermen referred to goliath groupers inhabiting hard substrates such as rocky reefs around islands and continental shores, submerged rocky outcrops and shipwrecks (juveniles and adults). At least two aggregation sites mapped (ranging from 2 to 60 individuals) could be concluded as spawning aggregation sites through evidence of high abundance and spawning activity. Priority research and conservation targets were identified and discussed for Babitonga Bay (e.g., design of a tagging experimental program and establishment of a marine protected area). Fishers' resource mapping provided a means of exchanging information among various disciplines while maintaining methodological rigor in a clear and straightforward way of presenting fishers' knowledge. The use of fishers' sketch maps is a promising tool for marine conservation in Brazil, with special regard to adaptive co-management regimes, where frequent environmental re-evaluations are needed.(AU)

A abundância relativa e agregações de meros Epinephelus itajara foram descritas e mapeadas através do conhecimento ecológico local de pescadores da baía Babitonga, sul do Brasil. Seis informantes muito experientes desenharam individualmente sobre uma imagem de satélite da área de estudo informações sobre abundância e distribuição de meros, seguindo-se de uma sobreposição das imagens em um mapa final. O mero ocorre ao longo de uma larga faixa de salinidade e profundidade (principalmente juvenis), de áreas estuarinas rasas (menos que 5 m de profundidade) com alta incidência de água doce, até ambientes costeiros marinhos (ao menos até 35 m de profundidade); (indivíduos maiores são mais comuns, alcançando mais de 300 kg). A espécie é também encontrada habitando substratos consolidados como recifes rochosos ao redor de ilhas e continente, parcéis submersos e emersos e naufrágios. Ao menos duas das agregações mapeadas (variando de dois a 60 indivíduos observados) puderam ser consideradas agregações reprodutivas através de evidências de alta abundância e atividade reprodutiva. Ações de pesquisa e conservação foram identificadas e discutidas para a baía Babitonga. O mapeamento de recursos possibilitou uma forma de trocar informações entre várias disciplinas, mantendo rigor metodológico e apresentando o conhecimento dos pescadores em uma forma clara e direta. O uso do mapeamento é uma ferramenta promissora para a conservação marinha, com atenção especial para abordagens de co-gestão adaptativas, onde frequentes reavaliações ambientais são necessárias.(AU)