Seasonal variability shapes resilience of small-scale fisheries in Baja California Sur, Mexico

The portfolio effect in a small-scale fishery reduces catch and fishing income variability in a highly dynamic ecosystem

It is an increasingly accepted idea that biological diversity stabilizes ecosystem processes and the services they provide to society. By reducing biomass fluctuation, biodiversity could mitigate the impact of changing environmental conditions on rural incomes as long as people exploits a diverse set of natural assets. This effect is analogous to the risk-spreading function of financial portfolios. This paper presents evidence of the portfolio effect for an open-access artisanal fishery in an estuarine ecosystem, located in a Colombian Biosphere Reserve. Using catch statistics from 2002 to 2018, we evaluate the contribution of catch diversity to the stabilization of fishing income. We find that changes in catch composition are related to seasonal and interannual variations in salinity conditions. The portfolio effect arises from asynchronous fluctuations of fish species due to fluctuating environmental conditions. Catch diversification, instead of specialization, help achieve resilient fisheries.

Fish provision in a changing environment: The buffering effect of regional trade networks

Local and regional trade networks in small-scale fisheries are important for food security and livelihoods across the world. Such networks consist of both economic flows and social relationships, which connect different production regions to different types of fish demand. The structure of such trade networks, and the actions that take place within them (e.g., people fishing, buying, selling), can influence the capacity of small-scale fisheries to provide sufficient fish in a changing social and ecological context. In this study, we aim to understand the importance of networks between different types of traders that access spatially-distinct fish stocks for the availability and variability of fish provision. We deployed a mixed-methods approach, combining agent-based modelling, network analysis and qualitative data from a small-scale fishery in Baja California Sur, Mexico. The empirical data allowed us to investigate the trade processes that occur within trade networks; and the generation of distinct, empirically-informed network structures. Formalized in an agent-based model, these network structures enable analysis of how different trade networks affect the dynamics of fish provision and the exploitation level of fish stocks. Model results reveal how trade strategies based on social relationships and species diversification can lead to spillover effects between fish species and fishing regions. We found that the proportion of different trader types and their spatial connectivity have the potential to increase fish provision. However, they can also increase overexploitation depending on the specific connectivity patterns and trader types. Moreover, increasing connectivity generally leads to positive outcomes for some individual traders, but this does not necessarily imply better outcomes at the system level. Overall, our model provides an empirically-grounded, stylized representation of a fisheries trading system, and reveals important trade-offs that should be considered when evaluating the potential effect of future changes in regional trade networks.

Resilience of small-scale marine fishers of Bangladesh against the COVID-19 pandemic and the 65-day fishing ban

In 2020, the COVID-19 pandemic-induced nationwide lockdown (March-May) and the conservation-related 65-day fishing ban (May-July) in Bangladesh restricted its small-scale fishing folks from fishing for an unprecedented 130 days. This study assessed the resilience of two small-scale fishing communities in Barguna and Cox's Bazar districts against these subsequent disturbances. The research developed a conceptual framework based on Zurich Flood Resilience Alliance's '5 C-4R Framework', which considers the relationships among a wide range of sources of resilience with livelihood capitals and resilience properties. By analyzing 100 interviews with marine fishers, this paper showed how weakened livelihood capitals affected the resilience of fishing communities. Dependency on a single income source, inadequate access to aid and financial and natural resources, lack of skills and knowledge on alternative livelihood options, absence of strong social protection and social networks, social inequalities, institutional incompetence, and lack of community leadership and cooperation severely affected fishers' resilience. This study revealed that financial capital is directly linked with all resilience properties that require special attention to ensure fishers' well-being. The paper recommended drastic investments in small-scale marine fishers through long-term livelihood improvement and asset creation, skills and knowledge development on natural-resource-based alternative income generation activities, and an exclusive social safety net program for these fisherfolks. The approach and findings of this study can guide other emerging economies who enjoy significant contributions from the marine fisheries sector to understand the resilience of their fishers and to address the prevailing challenges owing to the pandemic and other natural calamities.

Effects of recent thermal history on thermal behaviour, thermal tolerance and oxygen uptake of Yellowtail Kingfish (Seriola lalandi) juveniles

This study determined the physiological and metabolic responses of cultivated Yellowtail Kingfish (Seriola lalandi) juveniles in accordance with their recent thermal history. The fish were acclimated at 20, 23, 26, 29 and 32 °C for 21 days to determine the final preferred temperature, thermal tolerance and the effect of acclimation temperatures on their oxygen uptake and aerobic scope. The final preferred temperature of juveniles was established at 26 °C. The critical thermal maximum (CTmax) ranged from 34.2 to 36.9 °C, while the critical thermal minimum (CTmin) ranged from 10.9 to 17.3 °C, depending on acclimation temperature. With the CTmax and CTmin values, the thermal window was determined to have an area of 258°C², which is characteristic of subtropical organisms. Although, the metabolic rate was relatively constant (ranging 390.6-449.8 mg O₂ kg^-0.8 h^-1) between 20 and 26 °C (Q₁₀ = 1.6, 1.0), an increase to 544.8 mg O₂ kg^-0.8 h^-1 at 29 °C (Q₁₀ = 1.9) and decrease of 478.4 mg O₂ kg^-0.8 h^-1 at 32 °C (Q₁₀ = 0.6) were observed. The maximum value obtained for aerobic scope was 310.9 mg O₂ kg^-0.8 h^-1 at 26 °C. These results suggest that the acclimation temperature of 26 °C is an optimum thermal condition for a physiological and metabolic performance of yellowtail kingfish juveniles. On the contrary, the response observed during the evaluation of critical temperatures, oxygen uptake and aerobic scope indicated that yellowtail kingfish in the juvenile state could be vulnerable when it experiences for long periods (e.g., >21 days) temperatures above 29 °C. According to our results, the thermoregulatory behaviour of yellowtail kingfish in the juvenile stages could be one of the most important mechanisms to maintain its optimal physiological performance by actively selecting a stable thermal environment close to 26 °C. In addition, it was determined the limits of the pejus state of juvenile yellowtail kingfish at 29 °C, where an increase of oxygen uptake to maintain the aerobic energy metabolism was observed, this could certainly affect the growth of juveniles in culture systems if they do not return in a thermal range of 23-26 °C. These results can contribute to infer the different effects of acclimation temperature on the growth, thermal tolerance and respiratory capacity of S. lalandi juveniles on aquaculture systems.

Ecosystem service lens reveals diverse community values of small-scale fisheries

The ocean provides benefits to coastal communities around the world, however, the depth and complexity of people's interactions with marine ecosystems are not well represented in many marine management initiatives. Many fisheries are managed to maximize provisioning value, which is readily quantified, while ignoring cultural values. An ecosystem services approach that includes both provisioning and cultural services will enable managers to better account for the diverse values marine fisheries provide to coastal communities. In this study, we assess community values related to a top fished species, the Mexican chocolate clam, Megapitaria squalida, in Loreto, Baja California Sur, Mexico. We conducted an exploratory analysis based on 42 household surveys, and found that community members perceive multiple provisioning and cultural benefits from the clam, including community economic, historical, and identity values. Despite reporting infrequent harvest and consumption of clams, participants perceive the species as an important part of community identity, highlighting the role of Mexican chocolate clams as a cultural keystone species in the Loreto region. Fisheries management that recognizes the full range of ecosystem services a species contributes to coastal communities will be better equipped to sustain these diverse values into the future.

Mercury concentrations in Baja California Sur fish: Dietary exposure assessment

Total mercury concentrations ([THg]) in muscle were determined in commercial finfish and elasmobranchs from Baja California Sur (BCS), Mexico to evaluate dietary Hg exposure for BCS communities, including the relationship of trophic ecology, length and mass with [THg] that might drive future consumption advice (e.g., recommend limited consumption of large fish for some species). The [THg] ranged from 0.06 to 528.02 μg kg^-1 ww in finfish and 17.68-848.26 μg kg^-1 ww in elasmobranchs. Relative to the consumption threshold set for predatory fish in Mexico, all species had a concentration below 1000 μg kg^-1 ww. As expected, 16 (4.02%) and 75 (18.84%) individual fish were above advisory thresholds of 500 and 200 μg kg^-1 ww, respectively. The hazard quotients (HQs) in most species were significantly <1.0, only banded guitarfish showed a significant median HQ > 1.0. Thus, the relative level of risk of high Hg exposure is low for most species.

Multiple drivers behind mislabeling of fish from artisanal fisheries in La Paz, Mexico

Seafood mislabeling has the potential to mask changes in the supply of species due to overfishing, while also preventing consumers from making informed choices about the origin, quality and sustainability of their food. Thus, there is a need to understand mislabeling and analyze the potential causes behind it to propose solutions. We conducted a COI DNA barcoding study in La Paz, Baja California Sur, Mexico, with 74 samples from fish markets and 50 samples from restaurants. We identified 38 species sold under 19 commercial names, from which at least ∼80% came from local small-scale fisheries. Overall, 49 samples, representing 40% (95% CI [31.4-48.3]) were considered mislabeled in our samples. Based on analyses where species were assigned to three price categories, economic incentives were associated with approximately half of the mislabeling events observed, suggesting that other motivating factors might simultaneously be at play. Using a network approach to describe both mislabeling (when species are mislabeled as the focal species) and substitution (when the focal species is used as substitute for others), we calculated proxies for the net availability of each species in the market. We found that local fish landings were a significant predictor of the net availability of the 10 most important commercial species at retail, but this true availability was masked to the eyes of the final consumer by both mislabeling and substitution. We hypothesize that the level of supply of each species could help explain mislabeling and substitution rates, where species in low supply and high demand could show higher mislabeling rates and rarely be used as substitutes, while species in high supply and low demand could be used as substitutes for the preferred species. Other factors affecting mislabeling include national regulations that restrict the fishing or commercialization of certain species and local and global campaigns that discourage specific patterns of consumption. We discuss how these factors might influence mislabeling and propose some solutions related to communication and education efforts to this local and global challenge.

Seasonal variability in global industrial fishing effort

Human beings are the dominant top predator in the marine ecosystem. Throughout most of the global ocean this predation is carried out by industrial fishing vessels, that can now be observed in unprecedented detail via satellite monitoring of Automatic Identification System (AIS) messages. The spatial and temporal distribution of this fishing effort emerges from the coupled interaction of ecological and socio-economic drivers and can therefore yield insights on the dynamics of both the ecosystem and fishers. Here we analyze temporal variability of industrial fishing effort from 2015-2017 as recorded by global AIS coverage, and differentiated by fishing gear type. The strongest seasonal signal is a reduction of total deployed effort during the annual fishing moratorium on the numerically-dominant Chinese fleet, which occurs during boreal summer. An additional societally-controlled reduction of effort occurs during boreal winter holidays. After accounting for these societal controls, the total deployed effort is relatively invariant throughout the year for all gear types except squid jiggers and coastal purse seiners. Despite constant deployment levels, strong seasonal variability occurs in the spatial pattern of fishing effort for gears targeting motile pelagic species, including purse seiners, squid jiggers and longliners. Trawlers and fixed gears target bottom-associated coastal prey and show very little overall seasonality, although they exhibit more seasonal variation at locations that are further from port. Our results suggest that societal controls dominate the total deployment of fishing effort, while the behavior of pelagic fish, including seasonal migration and aggregation, is likely the most prominent driver of the spatial seasonal variations in global fishing effort.