In PaulRegular/MSP: Multispecies production model incorporating covariance

Introduction {-}

The concept of carrying capacity has long been foundational in applied population ecology, being widely used in the management of renewable resources [@hilborn1995; @chapman2018]. The understanding that populations produce more offspring than an environment can sustain led to the notion that the 'surplus' can be harvested sustainably [@pauly2021]. These ideas are exemplified by the use of maximum sustainable yield (MSY) in the classic single-species surplus production modeling framework [@schaefer1954]. In one equation, this framework attempts to explain interannual changes in biomass using fisheries landings and estimates of intrinsic growth rate and carrying capacity. Given the theoretical elegance of the approach, it has been both widely adopted and scrutinized. Estimates of carrying capacity, and resultant derivations of MSY, are frequently criticized for being time-invariant, which ignores the ubiquity of environmental variation [@del2004]. Moreover, traditional surplus production models tend to focus on single-species dynamics and often disregard the complexities arising from species interactions within ecosystems [@gamble2009].

Recognizing the limitations of single-species approaches, there have been calls to move towards an ecosystem-based approach to fisheries management [EBFM\; @latour2003]. EBFM acknowledges the intricate web of ecological interactions and aims to ensure the sustainability and integrity of marine ecosystems while supporting viable fisheries [@pikitch2004]. To successfully implement EBFM, it is crucial to develop models that account for species interactions and the dynamics of multiple species within the ecosystem. Substantial progress has been made in the development of multispecies models and a spectrum of approaches have been developed, ranging from complex models that attempt to account for all parts of marine ecosystems [e.g., @fulton2011] to multispecies age-structured assessment models [e.g., @albertsen2018] to multispecies surplus production models [e.g., @bundy2012; @gamble2009; @mueter2006]. However, the application of these approaches to fisheries management have often been hindered by data limitations (e.g., age data are frequently not available) and knowledge gaps (e.g., incomplete understanding of food-web interactions). There is therefore a need for methods to help bridge the gap between single-species and multispecies assessment in data or information poor systems.

In this paper, we borrow concepts from single-species surplus production modeling [@millar2000] and multispecies modeling [@albertsen2018] to construct a model that incorporates the impacts of fishing on single-species populations and accounts for species interactions within the ecosystem. The data requirements of this model are relatively minimal, requiring species-specific landings and survey indices of biomass. As a case study, we apply this model to commercially important demersal fish species off the east coast of Canada, specifically the Grand Banks of Newfoundland. This case study is particularly germane due to the widespread collapse of most stocks in the area during the early 1990s [@lear1998], leaving the relative contributions of fishing and environmental impacts uncertain [@pedersen2017]. Using this case study, we aim to reveal species interactions, distinguish the impacts of fishing from environmental effects, and demonstrate the utility of this modeling approach. The subsequent sections of this paper will present the conceptual framework of our model, describe its application, and discuss the implications of our findings for ecosystem-based fisheries management.

PaulRegular/MSP documentation built on Dec. 16, 2024, 1:59 p.m.