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Biodiversity along the West Coast of Vancouver Island: Lessons learned and application to the Strait of Georgia Ron Tanasichuk, Pacific Biological Station, Nanaimo, B. C. Email: [email protected] Ph. 250-756-7197 Biodiversity defined: Wikipedia: “Biodiversity is the degree of variation of life forms within a given species, ecosystem, biome, or an entire planet.” But from an ecosystem perspective, it's important to remember that it’s not just the biodiversity, but also how plants and animals interact. The monitoring of biodiversity variations and species interactions along the West Coast of Vancouver Island has given us novel insights of the biological bases of fish production variability, and the approaches used on the West Coast provide a model for monitoring biodiversity and ecosystem production in the Strait of Georgia. WCVI (La Perouse Bank) Study Area Fish production variability along the WCVI largely revolves around the production variability of one species of euphausiid (krill, Thysanoessa spinifera) The largest T. spinifera measured was 32 mm long and weighed 340 mg. It is not an overstatement that T. spinifera is the link between the sun and the production of many fish species on the WCVI. WCVI euphausiid/zooplankton monitoring programme, 1991present F We have done 177 cruises since 1991 and have measured and weighed over 162,000 euphausiids and 90,000 zooplankton T. spinifera biomass, 1991-2011 Annual median biomass has varied by 120-fold The proportion of total zooplankton biomass (open circles) accounted for by euphausiids has changed dramatically To learn about the variations in the productivity of any animal population we have to consider: 1) characteristics of the population itself (eg. parental abundance, “numbers of brothers and sisters”); 2) variations in prey availability; 3) variations in competitor abundance; and, 4) variations in predator abundance. Investigative science is based on hypothesis testing, using observation. We collected data for a number of years, even over several decades, so that we could test hypotheses related to the biological basis of herring and salmon production variability. An important fish predator and possible competitor: Pacific hake Hake biomass variability Hake biomass can range from insignificant to over 1,000,000 tonnes Emerging potentially important predators Humpbacks and sea lions are recovering dramatically Herring WCVI and Strait of Georgia herring show differing trends Prey availability for herring, 1991-2011 T. spinifera longer than 17 mm are the most important prey for herring; this prey accounts for about 7% of the total biomass of zooplankton; August is the critical period for energy accumulation; euphausiid peaks occur in August (open circles) in 6 of 21 years; biomass has varied by a factor of 800. The biological explanation for varying WCVI herring recruitment The biomass of T. spinifera > 17 mm in August of each of the first three years of life, and hake predation during the first year of life, explain changes in recruit herring (first-time spawners, Age 3) abundance. Open circles – observed recruitment; closed circles – predicted recruitment The biological explanation for varying survival rates of adult WCVI herring Survival rates decrease (mortality rates increase) with age, presumably because fish become progressively less efficient metabolically with age, but also decrease as the August biomass of T. spinifera longer than 17 mm declines. The biological explanation of WCVI growth variation The size of recruits is determined by T. spinifera biomass in August of each of the first three years of life. Size-at-age of older fish is essentially determined by recruit size and is affected to a lesser extent by T. spinifera biomass in August. 7 6 5 4 3 Numbers are age The salmon populations we consider Barkley Sound Juvenile Salmon Studies Goal of the research was to learn about distribution, migration timing, diet, and hatchery/wild fish interactions Variations in euphausiid prey for coho T. spinifera longer than 19 mm account for about 7% of the total biomass of zooplankton; biomass has varied by a factor of 700; peaks occur in May (open circles) in 5 of 21 years. The biological explanation for varying Carnation Creek coho returns Closed circles – observed return; open circles – predicted return Number of spawners, winter stream discharge, and marine prey (T. spinifera > 19 mm in May when fish enter the ocean) explained why total coho numbers vary. Variations in euphausiid prey for sockeye T. spinifera 3-5 mm account for about 0.05% of the total biomass of zooplankton; biomass has varied by a factor of 400; peaks occur in May (open circles) in 6 of 16 years. The biological explanation for Somass River sockeye return variability Somass River sockeye forecasts are based on the observation (Tanasichuk and Routledge 2011) that return variability is explained by variations in the biomass of 3-5 mm T. spinifera in May, when fish are migrating through Barkley Sound. Forecasts were inaccurate in 2010 and 2011. Closed circles – observed return; open circles – predicted return; dashed lines – 50% confidence interval. Age-specific responses to T. spinifera biomass suggest that each lake contains not one but six sockeye populations x - 2010 return year; o - 2011 return year; dashed lines - 50% confidence limits. 2011 forecast was inaccurate because of ages 3.2 and 4.2 returns. Results for Sproat Lake are comparable for these for Great Central Lake. Retrospective analysis of performance of euphausiid-based forecasts of Smith Inlet sockeye return Closed circles – observed return; open circles – predicted return; dashed lines – 50% confidence interval. WCVI euphausiid biomass measurements may have broader implications. Fraser River sockeye Total returns of the 19 monitored populations show a range of response to the effects of stock and T. spinifera biomass; closed circles - observed, open circles – predicted. The low return for 2009 was predicted in this analysis suggesting that the discrepancy between the conventional forecast and the observed return was a consequence of an inaccurate forecasting methodology rather than a real biological event. WCVI Summary and Conclusions 1. The lesson we have learned is that studies which use time series of observations of population characteristics, prey, competitors and predators provided the information that we needed to discover the biological bases of WCVI herring and salmon production variability; 2. It appears that some of the WCVI work has implications at a regional scale; 3. Based on the success of the WCVI studies, we can apply the WCVI study methodology to create a monitoring programme in the Strait of Georgia. 4. We will be able to use the results to learn the biological bases of production variability and then be able to make informed decisions about biological resource use to optimize ecosystem health and benefit to communities. Community-based Strait of Georgia nearshore marine ecosystem monitoring programme: An invitation Community locations are almost perfect for comprehensive programme; need more sampling locations in Gulf Islands. Work would pattern after Barkley Sound study and be bi-weekly (April – October) to monitor food, diet, distribution and abundance of hatchery and wild salmon. Sampling should beach- and purse seine fish collections and zooplankton sampling. Nanaimo River chum distribution Nearshore work in the late-70's suggests that juveniles may be highly concentrated in very shallow water suggesting that this is an important area to investigate. Proposed Strait of Georgia beachseine sites 154 sampling sites Google App technology can be used to input field data at the time of sampling using smart phones or tablets This means that data will be archived instantaneously and freely available. Strait of Georgia zooplankton monitoring transects 47 sampling sites Summary and Conclusions 1. Long-term monitoring of ecosystem diversity, including species interactions and variations in distribution and over time, are crucial to understanding, managing, and benefitting from biological resources; 2. Studies of the biological bases of herring and salmon production variability on the WCVI provide a framework for such work in the Strait of Georgia and, as importantly, show that these types of studies can help us learn about ecosystem structure and function; 3. The proposed Strait of Georgia ecosystem monitoring programme is an absolutely unique opportunity for the communities to share in learning about the biology of the Strait, and contribute to optimizing ecosystem health and benefit to the communities.