Spawning dynamics and parental effects
SSC: Joanne Morgan
Keynote speaker: Fran Saborido-Rey (Spain)
Spawning dynamics in fish are adapted to the seasonal dynamics of the plankton in the various marine ecosystems. High-latitude spring-bloom systems are at the one extreme end with a time- limited plankton production in spring/early summer. At the other end is found eastern boundary upwelling ecosystems that produce plankton year around. Match-mismatch between the environment and larval production and parental effects on offspring production and quality have been the focus of considerable laboratory, field and modeling investigations over recent decades and the implications for fisheries management are increasingly well understood. They provide a key mechanism for the past and present environment to impact future productivity. This session aims to synthesize new research into parental effects on spawning dynamics and place it in the context of population dynamics and stock recovery.
Early life stages and ‘the critical period’
SSC: Øyvind Fiksen
Keynote speaker: Myron Peck (Germany)
Hjort’s classic theory has influenced fisheries research for nearly 100 years despite empirical support remaining equivocal. Although solving the recruitment problem is no longer the Holy Grail of fisheries science recruitment variability remains central to population dynamics. Being aware of Hjort’s point of departure was the particular dynamics of a spring-bloom ecosystem, this session aims to describe how early life history stages impact recruitment across various types of ecosystems and identify the conditions where a process-based understanding of recruitment is achievable.
Spatial aspects and drift
SSC: Pierre Petitgas
Keynote speaker: Geir Huse (Norway)
Hjort’s second recruitment hypothesis addressed the fate of offsprings that drift out of areas suitable for their survival. This hypothesis has forged the concept of population as a closed life cycle, making adult spawning migration the contranatant necessary mechanisms balancing larval drift. Spatial losses to the population are represented by the larvae that die but also the larvae that survive outside the population current life cycle, e.g., colonizers potentially installing a new population. The challenge of testing spatial effects on the fate of populations is still linked to the vast limitations in sampling plankton as well as individual fish movements at sufficient spatial and temporal scales. Today, high-resolution circulation models are the basis for linked ecosystem models simulating production and distribution of plankton across trophic levels. Coupled individual-based models can simulate larval dispersal and growth as well as adult displacements.
Climate change impacts on larval connectivity and spawning habitats still represent knowledge gaps, making spatial aspects crucial for predicting how populations with complex life cycles may react as a whole. This session will therefore focus on the spatial dynamics of various life stages (larvae and adults) within an ecological framework, with field sampling and modelling approaches.
Natural mortality and growth
SSC: Richard Nash
Keynote speaker: Pierre Pepin (Canada)
Mortality is strongly size-dependent in marine organisms across all trophic levels, and mortality and growth are two opposing but inter-linked forces regulating the population dynamics of fish. The large mortality in small organisms can give large changes in net survival from small changes in mortality rate. Classical theory emphasizes the role of density-dependent and density-independent factors. More recent simulation-based studies have shown the consequences of variability in mortality and growth for management. This session aims to bring together empirical and conceptual insights into these key processes and address issues relevant for management.
Environmental drivers ‒ fluctuations and change
SSC: Coleen Moloney
Keynote speaker: William Cheung (Canada)
Sustainable fisheries management is enhanced and strengthened by ecosystem-based approaches to managing fish resources. Such management needs to be tailored to the specific structure and functioning of relevant ecosystems and to the environmental stressors of the various systems. Climate change and variability have been documented to have strong impacts on productivity, especially through impacts on plankton production. Ecosystem effects need to be integrated into analyses that provide information for the setting of fishing quotas. This session will consider environmental and ecological impacts on fish population dynamics occurring on broad space and time scales.
Exploratory analyses, uncertainty and predictions
SSC: Mark Dickey-Collas
Keynote speaker: Coilin Minto (Ireland)
When recruitment dynamics are considered within projections of stock dynamics, it is foolhardy not to incorporate uncertainty into the analysis. Quantifying all uncertainty is a challenge but as we explore management options under the precautionary approach; risks and tradeoffs become increasingly important. This session will explore how current techniques are including uncertainty in recruitment into stock projections for short term catch options, medium term evaluations of management plans and long term climate scenarios. Contributions will be encouraged from the Bayesian and frequentist worlds, that explore the paradigm of recruitment developed by Hjort in the multidimensional space that we now assume creates recruitment strength, and how we quantify uncertainty amongst many metrics