Modelling Ecosystem Processes Acting On Upper Trophic Level Managed Species in the Salish Sea – Lessons Learned and Future Goals

Ecosystem models provide a means to examine how large-scale drivers and food web interactions can influence change in marine species. Coho and Chinook salmon are iconic species in the Salish Sea and have been significant components of ecosystem models developed for its sub-basins. We present results from models of three regions in the Salish Sea: the Strait of Georgia, the Central Basin of Puget Sound, and the Southern Basin of Puget Sound. Each of these models provides reasonable simulations of how ecosystem-level mechanisms can influence changes in target managed species. While there is some overlap in these models’ ability to explore changes in mammals and fished species, regional differences remain that make it difficult to integrate knowledge at the scale of the Salish Sea as a whole. For example, the Strait of Georgia and Puget Sound models all suggest that bottom-up type dynamics have influenced the dynamics of many species. Significant contrast, however, can be seen in the dominance of the Central basin of Puget Sound by ratfish, approximately a third of all fish biomass whereas, in the Strait of Georgia, Pacific herring and small pelagic species account for a third of all fish biomass. Understanding these similarities and differences will help researchers explain why significant species like Coho and Chinook salmon can exhibit quite different population dynamics in regions of the Salish Sea. As part of an integrated project spearheaded by the Pacific Salmon Foundation and Long Live the Kings, we hope to increase the overlap in both species and mechanisms modelled in future iterations of these modelling efforts

The influence of geographic scale, climate and trophic dynamics upon North Pacific oceanic ecosystem models

Dynamic simulation models of three nested North Pacific ecosystems (the Strait of Georgia, the British Columbia Shelf and the Northeast Pacific) were constructed to examine how area scale affects modelled historic changes of trophic interactions, fisheries and climate. Species groups were the same for all ecosystem models, with a focus upon commercially important fish species. The models were dynamic and spanned the period from 1950 to the start of the 21st Century. Time series data for biological indicators were compared to predicted model time series, under different scenarios of ecosystem control: top-down, bottom-up, or combinations thereof. Results of these scenarios suggest that while fisheries, and predation / competition effects explain most population changes for commercially important fish species, all species modelled also appear to experience bottom-up effects driven by climate change, and regime shifts. The ecosystem models suggest such bottom-up dynamics through predicted primary production anomalies similar to decadal cycling seen in climate indices like the Pacific Decadal Oscillation (Northeast Pacific), upwelling at 54°N (BC shelf) and Salinity / Fraser River discharge (Strait of Georgia). The results of this work suggest that both the area and scale over which indices of regime shifts and climate change are measured are linked, via bottom-up forcing, to changes in biomasses of all trophic levels in these ecosystems. The ability to link bottom-up and top-down dynamics provides an exciting way for ecosystem models to contribute to the formulation of policy and cross validation of single species stock assessment research.Science, Faculty ofResources, Environment and Sustainability (IRES), Institute forGraduat

An interdisciplinary assessment of tropical small scale fisheries using multivariate statistics

Interdisciplinary fisheries information pertaining to sustainability were analysed with the multivariate techniques of multidimensional scaling and cluster analysis to determine how information from outside biology might help augment biological fisheries analyses or warn when more in depth biological assessments might be needed for a fishery. Tropical small-scale fisheries were used as a test model for collecting this data set as a high percentage are subject to overfishing. Defining the nature and causes of overfishing in these fisheries may help in the development of appropriate solutions to maintaining sustainability of associated fisheries, ecosystems, and communities of fishers using these resources. Measuring the sustainability of tropical small-scale fisheries was examined from the perspective of'Malthusian overfishing', that is, overfishing due to populations increasing at a rate beyond the capacity of the resource base to supply. The mechanism of Malthusian overfishing contains three processes; increased populations, increased competition, and increased use of destructive gears. In order to identify fisheries subject to Malthusian overfishing, 54 tropical small scale fisheries were described using sustainability attributes from four fisheries disciplines; biology, economics, sociology, and technology. While information from economics seemed to be disjointed from the biological indicators of sustainability, the sociological and technological results proved complementary to those from biology. The reasons for these different congruencies are discussed. The implication of this work is that non biological information may be helpful to amplify biological warnings of overfishing as well as identify fisheries in need of greater scrutiny.Science, Faculty ofZoology, Department ofGraduat

Fisheries Centre research reports, Vol. 9, no. 6

Science, Faculty ofOther UBCOceans and Fisheries, Institute for theUnreviewedGraduat

Changes in the diet composition of juvenile sockeye salmon in the Strait of Georgia from the 1960s to the present Changes in the diet composition of juvenile sockeye salmon in the Strait of Georgia from the 1960s to the present

Abstract Studies of the diet of juvenile sockeye salmon in the Strait of Georgia over the past 40 years show a trend of decreasing consumption of copepods and increasing consumption of decapod zooea and larvae. Presently, amphipods and decapods are the dominant prey items on the diet, representing approximately 60% of a relatively restricted number of items. The dominance of decapods in the diet appeared to be unique among the diets of juvenile salmon examined in other studies. Amphipods were usually the most common diet item in all examined studies of juvenile sockeye salmon diets. Studies of the diets of juvenile sockeye salmon, including our own, provide patchy information about a critical period in the establishment of brood year abundance. More comprehensive studies are needed that monitor the diets of juvenile sockeye salmon throughout the early marine period in relation to the composition of their zooplankton prey items

An ecosystem model simulating historic changes and forecasting future long-term upper trophic level species dynamics in South Puget Sound

We built an ecosystem model to emulate changes in the biomass and mortality rates of managed species in South Puget Sound from 1970 to the present and simulate likely changes to the year 2054. Our model simulates historic primary production variation to emulate observed changes in the biomass and mortality of upper trophic level species in South Puget Sound. The emulation of historic dynamics uses time series from monitoring work on many marine species in South Puget Sound including birds, mammals, salmonids, demersal fish, shellfish, eelgrass, kelp and phytoplankton. Time series of resampled historic primary production changes were used to develop forecasting scenarios of potential long-term changes in the biomass of managed species under a variety of fishing and aquaculture policies. Our results suggest that current fisheries and aquaculture policies foster the rebuilding of many managed marine species in South Puget Sound. Our results also suggest that dramatic increases in aquaculture would have little to no effect on the trophic dynamics of most species in South Puget Sound. This modelling work provides a convenient and cost effective way to decide where monitoring resources may best be devoted. Our model identifies which species are more likely to experience significant change to their biomass and/or mortality rates in the future given a variety of natural and anthropogenic sources of change. Our model can also be used to examine how different management policies may attenuate or exacerbate likely dynamics for given species in South Puget Sound

Fisheries Centre research reports, Vol. 6, no. 3

The third Fisheries Graduate student symposium was held at the Ralf Yorque room of the UBC Fisheries Centre, from March 21 to March 23, 1997. Attendees included 16 students from the UBC Fisheries Centre, 5 students from the School of Fisheries and School of Marine Affairs, University of Washington, 6 students from the School of Resource Management, Simon Fraser University and 1 student from the Department of Biology, University of Victoria. The symposium was organized in four general subjects: ecosystems and fisheries; fish population dynamics and behaviour; climate and fisheries; and fisheries management. There was much discussion and an open exchange of views as the participants took advantage of an opportunity to discuss their research without the perception of pressure from advisors, faculty, or established researches. The conference was a success, illustrative of the high quality of fisheries research that is being conducted in the Pacific Northwest. Next years symposium will be held at the School of Fisheries, University of Washington.Science, Faculty ofOceans and Fisheries, Institute for theUnreviewedGraduat