The workshop consisted of five oral presentations in the morning, including talks by invited speakers Myron Peck (University of Hamburg, Germany) and Shin-ichi Ito (Tohoku National Fisheries Research Institute, Japan), followed by a productive afternoon discussion period. Altogether, 19 people participated in the workshop. In addition, it featured what had to be the largest banner of all sessions and workshops (Fig. 1).
Following initial remarks by workshop co-conveners Sukyung Kang and William Stockhausen, invited speaker Myron Peck discussed recent advances in, and future challenges to, integrating physiology, behavior, and physical constraints into coupled IBMs/CBPMs for the early life stages of marine fish.
In a wide-ranging talk, Dr. Peck highlighted the diverse physiological mechanisms and responses to environmental conditions that need to be accounted for in modeling the growth and survival of early (and later) life stages of marine fishes on an individual basis. These include direct effects of temperature and size on growth and survival through egg development rates, hatching success, size-at-hatch, yolk sac utilization rates, routine metabolism rates, and swimming speed.
Parental effects on egg survival, environmental effects on success of first feeding success, changes in diet composition and prey energy content, flexibility in foraging behavior, and species interactions were also discussed. Among his recommendations, Dr. Peck stressed the importance of increased knowledge of the growth physiology of target species and the need for modelers to conduct sensitivity studies to identify critical model parameters.
Shin-Ichi Ito, the second invited speaker, discussed the importance of incorporating feeding and spawning migrations in models for growth and survival of marine fishes. He presented results from a comparison of such models for Japanese sardine (Sardinops melanostictus) in the western North Pacific. Dr. Ito's talk highlighted the importance of confronting observed spatial patterns (based on field data) with multiple alternative models because different behavioral mechanisms can give rise to similar spatial patterns. In the study he recounted, Dr. Ito and colleagues were able to eliminate two of four hypothesized behavioral mechanisms for observed sardine feeding migrations from further consideration; however, they were unable to discriminate between the remaining two mechanisms, even though the behavioral bases for these models were quite different (predator avoidance vs. extended kinesis). Dr. Ito also presented a rather novel approach, based on artificial neural networks, to "forcing" a spawning migration pattern when hypothesized behavioral mechanisms were inadequate to reproduce observed movement patterns.
Fittingly, (given the venue), the other speakers presented talks featuring models and data relevant to Korean marine systems. Jung-Jin Kim (Ph.D. student, Pukyong National University, Korea) used a coupled IBM/CBPM to infer current seasonal spawning grounds for Korean common squid (Todarodes pacificus) in the western Pacific from field data for larval occurrence. He then used IPCC model runs to drive a regional ocean model to predict changes in spawning grounds under future climate change. Dr. Sukgeun Jung (Jeju National University, Korea) presented preliminary results for a coupled IBM/CBPM for Pacific anchovy (Engraulis japonicus) in Korean waters. And finally, Min-Jung Kim (NFRDI) presented results from diet studies on Pacific anchovy in the southern coastal waters of Korea. Ms. Kim's talk highlighted the spatiotemporal and ontogenetic variability in anchovy diets in southern Korean waters due to variability in prey species composition and abundance, plasticity in feeding strategies, and ontogenetic differences.
A key outcome from discussions following the presentations was the recognition that one aspect of the impact of future climate change on species abundance and distribution patterns will occur through changes in the growth rates and subsequent survival of individuals. However, these changes may not be predictable from simple statistical relationships based upon (current) growth rates and expected changes in temperature. Instead, it is likely that future changes will be due to the dynamic interaction of several factors, including indirect effects on the abundance, composition, and relative energy content of key prey species. These indirect effects will act in concert with direct effects, such as changes in water circulation patterns and temperature, which will influence the spatial overlap and metabolic processes of predators and prey.
Thus, one important recommendation stemming from the discussions was that IBMs used to predict the impact of future climate change on species abundance and distribution should incorporate mechanistic bioenergetics models that account for effects of changes in prey abundance, energetic content, and species composition on individual growth rates. Workshop participants also acknowledged a general lack of data on the physiology of many fish and shellfish species, even for commercially- and/or ecologically-important ones, as well as a scarcity of marine physiologists who could potentially address these issues.
A list of additional recommendations from the workshop include:
Incorporating life-cycle closure within physiologically-based models to capture climate impacts on various life stages (and identify potential climate-driven bottlenecks to recruitment), with a recognition of stage-specific differences in growth physiology, diets, and tolerance to environmental factors
Increasing process-level understanding of the factors controlling fish migration patterns, particularly spawning migrations, and the environmental factors that regulate behaviorally-mediated movements or the evolution of observed behaviors of different life stages
Conducting more basic, controlled laboratory experiments on the growth physiology of species, including experiments designed to capture the interactive effects of multiple factors (e.g., temperature x prey species x pH).
