Small Pelagic Fish Research at SAFS

AP: What was the focus of your research?

TE:Members of my lab and I are interested in understanding how to better manage fisheries for small pelagic fishes (SPF) to protect their ecological role in food webs. We are using various tools, including simulation modeling and data synthesis, to explore trade-offs generated by fishing forage fish and to reveal the “footprint” of fishing on small pelagic fishes.

AP:Felipe Hurtado and I are involved in the re-evaluation of the harvest control rules used by the Pacific Fishery Management Council to manage the fishery for Pacific sardine. Felipe has developed a framework to evaluate the trade-offs between the size of catches and the risk of the population dropping to undesirably low levels. He has applied this framework to the SPF fishery off southern Australia.

LH:Herring are structured into easily identifiable spawning assemblages, but their genetic structure is in dispute. With funding from Washington Sea Grant, Eleni Petrou and I are using genetic markers to identify isolated populations among these spawning assemblages. We are also developing genetic markers that can be used on herring bones dating back several thousand years and will integrate this research with traditional ecological knowledge of tribal elders in Washington State and British Columbia.

TB:The Pacific herring population in Prince William Sound, Alaska, crashed shortly after the Exxon Valdez oil spill and has yet to recover. As a result, commercial fishing on herring in the Sound has been closed for more than 20 years, resulting in approximately $230 million in lost income for Alaskan communities. Many questions persist regarding the extent of the spill’s influence on the crash and continued low abundance of herring. The research being conducted in my lab focuses on improving the assessment model that the Alaska Department of Fish and Game uses.

AP: What have you learned?

TE:That is complicated! There are a lot of pathways in food webs, so it is remarkably difficult to predict exactly how a change in fishing policy can affect ecosystems. That said, we have identified some fairly simple rules that, if followed, would avoid the worst ecological outcomes at very little cost to fisheries. Also, we find that you often don’t need to know all of the specifics of ecological interactions to derive sensible fishing policies. In addition, there are some easy ways to spot which small pelagic fish is a “key” species in food webs.

AP:There are strong trade-offs among the management objectives, as expected. While prohibiting directed fishing below a certain level of biomass can lead to much lower risk without major losses in expected catch, setting this level too high can lead to frequent closures of the fishery, which is a bad outcome.

LH:Some spawning assemblages are more isolated from each other than is commonly assumed, especially if they are isolated by geography or spawn at different times. For example, at least three genetically differentiated herring populations exist in Puget Sound.

MM:The model estimates a 55% probability that the biomass of age-3 and older herring was below the management threshold of 22,000 short tons in 2013.

AP: How does your research help us manage small pelagic species sustainably?

TE:The key question is whether SPFs are more valuable in the ocean, feeding other highly valuable predators, or as a commodity to be fished. Our work is developing tools to answer this question. In addition, we have identified a common pattern in the collapse of small pelagic fisheries that can easily be avoided by adopting a more precautionary approach.

AP:Our work is feeding directly into the management pro-cesses for fisheries off the US west coast and Australia. For example, recently the Scientific and Statistical Committee of the Pacific Fishery Management Council changed how it sets overfishing levels for Pacific sardine based on the results of our research.

LH:The extent of population structure is important for management because weaker populations have to be managed independently to protect them from over-exploitation. The conservation of population diversity is important for management because it increases the resilience of the species as a whole to environmental perturbation. Estimating past abundance of genetically divergent populations from archaeological bones will provide important clues about population diversity before commercial fishing began.

MM:We can estimate the risk associated with different management decisions for Prince William Sound herring and test alternative hypotheses for the herring decline.

AP: Who are you working with on this project?

TE:An army of colleagues: Steve Munch (NOAA Fisheries), Eva Plaganyi (Commonwealth Scientific and Industrial Research Organisation, CSIRO), Bill Sydeman and Julie Thayer (Farallon Institute), and my entire lab group.

AP:Like Tim’s research, our work is highly collaborative. In relation to Pacific sardine, we constructed our models using fishery data from Kevin Hill (NOAA Fisheries) and environmental data from the California Cooperative Ocean and Fisheries Investigations. We have had feed-back on our work from the Pacific Fishery Management Council’s advisory bodies. They have advised us on which strategies to test and how to present results in a way that is useful for decision making. The work in Australia is in collaboration with scientists at CSIRO.

LH:I am working closely with managers at the Washington Department of Fish and Wildlife and increasingly with local Tribes, especially the Suquamish. We also collaborate closely with the Herring School (a coast-wide group of academics), Canadian First Nations, and resource managers. And, we are collaborating with the Department of Archaeology at Simon Frazer University and participating in a project funded by the Canadian government to investigate the importance of stock structure for stock assessment and ecosystem-based management.

MM:Our work is part of a larger research and monitoring effort—which combines a group of approximately 15 experts in the fields of oceanography, disease pathology, fish and marine mammal ecology, and population modeling—to better understand what is happening to Prince William Sound herring.

AP: What is next?

TE:We need some testing of possible fishing strategies with realistic population dynamics. Existing modeling assumes that small pelagic fishes behave like other stocks. We know that this isn’t the case; they are highly sensitive to environmental conditions and undergo long-term population cycles. I want to test some management strategies to determine which are robust to population cycles and predator characteristics while also ensuring fishing opportunities.

AP:Our work on Pacific sardine on the US West Coast and the small pelagic fisheries off Australia has focused on direct impacts of fishing. Like Tim, we are interested in the ecosystem impacts of fisheries for small pelagic species. We are working to link our population models with ecosystem models to better understand those indirect effects as part of the Ocean Modeling Forum.

LH:Eleni Petrou already had a successful sampling trip to the British Columbia coast. We will now develop a way to increase the number of suitable genetic markers. We are also developing protocols for interviewing tribal elders that will be used to collate traditional ecological knowledge and information on the cultural significance of herring.

MM:We will determine the relative value of each input data type supplied to the assessment, which has practical implications for guiding managers and scientists in their data collection efforts.

Richard Reid (Heiltsuk Integrated Resource Management Department), Eleni Petrou (SAFS), Kira Krumhansl (Simon Fraser University) collecting fin samples from Pacific herring along the Central Coast of British Columbia. Photo: Mark Wunsch