Citation: Pellowe, K. E., and H. M. Leslie. 2020. Size-selective fishing leads to trade-offs between fishery productivity and reproductive capacity. Ecosphere 11(3):Abstract. Most fishing is inherently size-selective, in that fishers preferentially select a subset of the population for harvest based on economic incentives associated with different-sized fish. Size-selective fishing influences the targeted population and fishery performance in multiple ways, including changing the reproductive capacity of the target population and altering fishery yield. Understanding how socialecological variability, including size selectivity, affects target species populations is critical for fisheries management to optimize the benefits of fisheries and the ecological impacts on target populations. In this study, we used yield per recruit, spawning stock biomass per recruit, and length-based spawning potential ratio models to explore how a range of size selectivity scenarios affect fishery and population productivity for Mexican chocolate clams, Megapitaria squalida, in Loreto, Baja California Sur, Mexico. We found that alternate slot limits result in trade-offs between fishery yield and reproductive productivity of the target population. A more restrictive slot limit reduced the proportion of the population available to harvest, resulting in higher reproductive capacity of the population, compared to a less restrictive slot limit, conditional on the rate of fishing mortality. In the long run, a more restrictive slot limit will likely lead to a higher number of recruits, larger stock size, and higher long-term fishery yield relative to a less restrictive scenario. Our findings highlight that how people fish matters, perhaps as much as the quantity of fish harvested; size-selective fishing that aligns with the life history of target populations and stakeholders' goals is critical to sustaining fisheries and the valuable food and livelihoods they provide.

Small-scale fisheries are an important source of food and livelihoods to coastal communities around the world. Understanding the seasonality of fisheries catch and composition is crucial to fisheries management, particularly in the context of changing environmental and socioeconomic conditions. While seasonal variability directly impacts the lives of fishers, most fisheries studies focus on longer-term change. Here we examine seasonal variability in the small-scale fisheries of Baja California Sur, Mexico based on 13 years of government fisheries data. We investigate how four fisheries indicators with direct relevance to ecological resilience–magnitude and variance of landed fish biomass, taxon richness and the proportion of top-trophic-level taxa in total catch–vary within and among years and at multiple spatial scales. We find that these resilience indicators vary both seasonally and spatially. These results highlight the value of finer-scale monitoring and management, particularly for data-poor fisheries.

Temporal variability driven by environmental shifts, biological processes, and socioeconomic fluctuations is inherent in natural resource-based sectors, including fisheries. In navigating these changes as opportunities for transformation, individual decisions play a key role. Understanding individual adaptive capacity, i.e., the ability to cope under changing or novel circumstances, and considering how this capacity is affected by diverse individuals' interactions with formal fisheries policy may allow a better understanding of adaptive capacity in a rapidly changing world. In Loreto Bay National Park, Baja California Sur, Mexico, the Mexican chocolate clam is an important source of food and livelihoods and is harvested by a diverse group of fishers. Understanding the diversity of fishers, their decision-making processes, and their adaptive strategies is essential for both anticipating fishery outcomes and predicting the capacity of different types of fishers to adapt to environmental and economic change. We used semistructured interviews with clam harvesters to ask: (1) What types of fishers exist within the chocolate clam fishery? (2) How do they differ in their adaptive strategies? and (3) What are the implications of diverse fisher types on individual adaptive capacity? We find that fishers of chocolate clams in this region operate within both the formal and informal sectors, have varied fishing strategies, and can be characterized into four discrete types. We also find that heterogeneity among fishers affects their individual capacities to adapt to changing conditions and disturbances, and fisheries policy constrains fishers' access to options by limiting secure access to fishing rights. Maintaining a diverse suite of adaptive strategies is essential for individuals to cope in the face of future disturbance and change. Likewise, maintaining heterogeneity in the fishery, by ensuring that multiple fisher types are equipped to adapt to future change, will strengthen adaptive capacity within the fishery and community.

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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.

Alphabetical order core team starting here. ‡ Alphabetically senior team.

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