The effect of sea surface temperature on the structure and connectivity of species landings interaction networks in a multispecies recreational fishery.

Multispecies fisheries, particularly those that routinely adapt the timing, location, and methods of fishing to prioritize fishery targets, present a challenge to traditional single-species management approaches. Efforts to develop robust management for multispecies fisheries require an understanding of how priorities drive the network of interactions between catch of different species, especially given the added challenges presented by climate change. Using 35 years of landings data from a southern California recreational fishery, we leveraged empirical dynamic modelling methods to construct causal interaction networks among the main species targeted by the fishery. We found strong evidence for dependencies among species landings time series driven by apparent hierarchical catch preference within the fishery. In addition, by parsing the landings time series into anomalously cool, normal, and anomalously warm regimes (the last reflecting ocean temperatures anticipated by 2040), we found that network complexity was highest during warm periods. Our findings suggest that as ocean temperatures continue to rise, so too will the risk of unintended consequences from single species management in this multispecies fishery.

Effectiveness of Adaptive Real-Time Closures for Managing Migratory Species in Data-Limited Multispecies Fisheries

Fixed closure (FC) is a standard fisheries management tool for protecting sensitive species or species requiring conservation. However, an FC might not effectively manage migratory species because of the large uncertainties of their migration. Adaptive real-time closure (ARTC) is a tool that updates closure areas according to the latest information. This study aimed to evaluate the effectiveness of ARTC to conserve sensitive species for data-limited fisheries by a series of simulations using migration models with hotspots. In the single species simulation, the conservation ratio for the sensitive species in FC varies widely at greater migration uncertainty. In ARTC, a longer duration of a hotspot resulted in a higher conservation ratio. When the mean duration of hotspots was medium or long, the conservation ratio for the sensitive species was more than 50 % in more than 99 % of the simulation trials. In multispecies fisheries, a clear trade-off was observed between the conservation ratio of sensitive species and other species. ARTC was more effective than whole closure when the proportion of sensitive species was high or without closure when the proportion was low. Conditions in which ARTC was most appropriate were described for hotspot duration, increased numbers of individuals in a hotspot, and the relative value of conservation, representing the ratio of the value of conserving sensitive species to one of catching other species.

Identifying Pathways for Climate-Resilient Multispecies Fisheries

Fish live in communities, and most fisheries catch multiple species, yet fishery management predominately focuses on single species. In many multispecies fisheries, a variety of species are generally caught together at similar rates. Failure to account for this adequately in management has resulted in serial depletion and alterations to the ecosystem. Ideally, multispecies fisheries management should strive to produce good yields from specific valuable stocks and avoid adverse impacts of fishing on marine ecosystems. Moreover, multispecies management should aim to build resilience to changes in stock productivity and distribution driven by climate change. Here, we present tools and pathways that seven fisheries are adopting to achieve these goals. These case studies – from Mexico, Cuba, and Chile – differ in data richness, governance structure, and management resources. The management systems are also in various stages of evolution from unmanaged to complete management of a single species but transitioning to multispecies management. While various analytical tools and decision-making processes are described in the case studies, a common feature is the use of participatory stakeholder processes to build capacity and socialize the importance of multispecies management. We use lessons from these cases to recommend a multispecies management approach to overcome the limitations of current practices (typically single-species catch limits or large spatial restrictions), using the participatory processes and data-limited assessments to create stock complexes that simplify multispecies management (i.e., the “fish baskets” approach). Indicator species for each fish basket are identified to support the development of fishery performance indicators, reference values, harvest control rules, and management measures to create an adaptive management cycle to enhance the fishery’s resilience to impacts induced by climate change and other factors.

Modeling the Dynamics of Multispecies Fisheries: A Case Study in the Coastal Water of North Yellow Sea, China

Ecosystem models have been developed for detecting community responses to fishing pressure and have been widely applied to predict the ecological effects of fisheries management. Key challenges of ecosystem modeling lie in the insufficient quantity and quality of data, which is unfortunately common in the marine ecosystems of many developing countries. In this study, we aim to model the dynamics of multispecies fisheries under data-limited circumstances, using a multispecies size-spectrum model (MSSM) implemented in the coastal ecosystem of North Yellow Sea, China. To make most of available data, we incorporated a range of data-limited methods for estimating the life-history parameters and conducted model validation according to empirical data. Additionally, sensitivity analyses were conducted to evaluate the impacts of input parameters on model predictions regarding the uncertainty of data and estimating methods. Our results showed that MSSM could provide reasonable predictions of community size spectra and appropriately reflect the community composition in the studied area, whereas the predictions of fisheries yields were biased for certain species. Errors in recruitment parameters were most influential on the prediction of species abundance, and errors in fishing efforts substantially affected community-level indicators. This study built a framework to integrate parameter estimation, model validation, and sensitivity analyses altogether, which could guide model development in similar mixed and data-limited fisheries and promote the use of size-spectrum model for ecosystem-based fisheries management.

Vulnerability and Decision-Making in Multispecies Fisheries: A Risk Assessment of Bacalao (Mycteroperca olfax) and Related Species in the Galapagos’ Handline Fishery

Marine fish populations can be vulnerable to overfishing, as a response of their life history, ecology, and socio-economic aspects. Vulnerability assessments, in this regard, can be used to support fisheries decision-making by aiding species prioritization. Assessments like Productivity–Susceptibility Analyses are well suited for multispecies fisheries, with low gear selectivity and insufficient fishery-independent and dependent data. Using this method, we assessed local vulnerability of the Galapagos grouper (‘bacalao’; Mycteroperca olfax) and compared it with other phylogenetically-related species caught in the Galapagos’ handline-fishery. Bacalao is an overfished regionally endemic fish species, characterized by low resilience, high market and cultural value and high spatial overlap with the fishery. Our results suggested that bacalao is a species of high management priority, requiring urgent measures to prevent fisheries’ collapse. In addition, if current fishing pressure persists, other related species may become threatened in the near future. We also evaluated different management scenarios using this approach. Results suggested that the inclusion of additional no-take zones in the marine reserve, comprising key nursery habitats (such as mangroves) and spawning aggregation sites, would be necessary to reduce species vulnerability and to benefit other related species. Improving enforcement and fishers’ compliance are essential to guarantee the effectiveness of these measures.

Validation of a feedback harvest control rule in data-limited conditions for managing multispecies fisheries

Harvest control rules (HCRs) for sustainable fishery management have been developed for data-limited fish species for which stock assessments cannot be conducted. However, HCRs have largely not considered mixed-species catches, as when fishing-effort data are widely pooled for numerous minor species in a multispecies fishery. Presently, a feedback HCR has been successfully applied in Japanese fisheries management. By combining management strategy evaluation with a simulation to generate mixed-species data from a multispecies fishery that assume constant catchability (q) among species, we evaluated the performance of this feedback HCR and then compared its performance using species-specific data. In most cases, the biomass was controlled over that needed for maximum sustainable yield (MSY), and the fishing effort was under the fishing mortality consistent with achieving MSY (FMSY). However, for slow-growing species, the biomass might become lower than what is required to remain capable of producing MSY, even though fishing effort was controlled under FMSY. The results show that the feedback HCR is appropriate for multispecies fisheries management where only mixed-species data are available but with special monitoring for slow-growing minor species.