Letter to All Chiefs

Page 1 of 2 March 5, 2004 Volume VIII Issue 4 PRELIMINARY REPORT ON optimum escapement required to as Anstey Arm, where densities are SOCKEYE FRY IN QUESNEL AND maximize production (Hume et al. usually low. In the fall of 2003, we SHUSWAP LAKES IN 2003 1996; Shortreed et al. 2000). Given estimate there were a total of 123 the high escapements to both lakes million fry (+/- 95% C.I. = 20%) in By Jeremy Hume, Ken Shortreed, in 2002, we expected that fry Shuswap and Mara lakes. The data and Steve MacLellan recruitment to the lakes in 2003 indicate that in Shuswap Lake, fall would be very high, and would fry abundance peaks at In 2002, the sockeye escapement of possibly greatly exceed the escapements of about 1.0 million 5.5 million to Shuswap Lake was the productive (rearing) capacity of both EFS (~2.0 million total escapement) highest ever recorded. Of this lakes. To test this, we obtained and that fall fry numbers are the number, 2.9 million were females juvenile sockeye salmon population same or lower at all higher which spawned successfully estimates by conducting acoustic escapements (Fig. 1). While we (effective female spawners - EFS). and trawl surveys on Quesnel Lake didn't obtain a summer estimate in In Quesnel Lake in 2002, a direct in the summer (July 29) and fall 2003, summer estimates from estimate of spawner numbers was (Sept 23) of 2003 and on Shuswap previous years also indicate no obtained only for the Mitchell River. Lake in the fall (Oct 23) of 2003 (as increase in fry abundance above an However, based on the Mitchell in Hume et al 1996). These surveys EFS of around 1.0 million. In River escapement relative to the provided abundance, distribution, Shuswap Lake, fall fry size changes Horsefly River and other spawning survival, size, and diet information of relatively little over a wide range of areas in the previous year, we sockeye fry from the 2002 spawner numbers (Fig. 3). Average estimated the total escapement to escapement. In conjunction with this size is about 2.3 g at escapements Quesnel Lake in 2002 was 3.8 study, we also carried out a over 0.6 million EFS. In 2003, fry million. A slightly lower total limnological investigation of Quesnel averaged 2.0 g, within the range of escapement estimate of 3.1 million Lake to determine the effects of the sizes previously observed. was developed by the Pacific high escapements on lake Salmon Commission (PSC) using productivity. In addition, the Quesnel Lake DNA analysis of Quesnel sockeye Provincial Ministry of Water, Land, The estimated escapement of 1.3 collected in the lower Fraser River at and Air Protection (MWLAP) has million EFS to Quesnel Lake was Mission (Steve Latham, PSC, been conducting surveys of the the largest subdominant personal communication). In this kokanee and rainbow trout in escapement ever recorded to that report, we used the PSC estimate of Quesnel Lake and have reported lake and it followed the highest 3.1 million. Using this estimate as preliminary results (Sebastian et al. dominant escapement ever well as the EFS and prespawning 2004). In this report, we compare recorded to Quesnel Lake. We mortality proportions in the Mitchell the 2003 juvenile sockeye data with estimate there were a total of 76.2 River in 2002, we estimate the total similar data collected from both million fry (+/- 95% C.I. = 22%) in EFS to Quesnel Lake in 2002 was these lakes for up to19 previous the lake in the summer of 2003 and 1.3 million. For a number of years years, which include a wide range of 51.3 million fry (+/-95% C.I. = 22%) we have been performing spawner escapements. in the fall. Sockeye were distributed hydroacoustic and trawl surveys on throughout the lake at moderate Shuswap and Quesnel lakes to Shuswap Lake densities (max = 6,000/ha) and in obtain estimates of numbers of The escapement of 2.9 million EFS some areas such as the East Arm, juvenile sockeye in the lakes. These to Shuswap Lake was one million fish densities were higher than estimates are used through PSARC greater than in the previous record previously observed. The data in stock forecasting (Cass et al. year (1990), but did not produce any indicate that in Quesnel Lake, 1995 and Cass 1996 annually). more fall sockeye fry than in many maximum fry abundance is reached They have also been used to years of lower escapements (Fig. 1). at an escapement of 0.75-1.0 million develop and test fry-based and Densities were high in some parts of EFS (~1.5 to 2 million total habitat-based (PR model) empirical the lake (12,600/ha in one part of escapement) (Fig. 2). Beyond these models which predict rearing Salmon Arm) and were higher than escapements, summer and fall fry capacity of the lakes and the previously observed in areas such numbers do not increase. In Fraser River Aboriginal Fisheries Secretariat, 274-A Halston Connector Road, Kamloops, BC V2H 1J9 Phone (250) 828-2178 Fax (250) 828-2756 Email [email protected] Website http://www.frafs.ca Page 2 of 2 March 5, 2004 Volume VIII Issue 4 Quesnel Lake, fall fry average about trophic levels. These could include escapements to these systems to 3.5 g at moderate escapements. At spawning ground limitation, the high increase overall productivity. higher escapements, size is more abundance of a phytoplankton variable (Fig. 3). Fry collected in the species that is resistant to grazing The other difficulty posed by this fall of 2002 and 2003 were among by zooplankton, unusually warm large single event, lies in the the smallest ever recorded (2.7 and water in the summer of 2003, or assessment of other benefits. For 1.9 g, respectively) from Quesnel carry-over effects from the high fish example, with large escapements, Lake. However, fall fry from the densities in 2002. Further data and spawning gravels not utilized for 1993 brood year, a year with a analysis are needed to better some time are cleaned, old similar high escapement, averaged understand both this and the longer- spawning habitats used again, and 4.0 g, larger than the long-term term effects of the high portions of watersheds may be re- average fall fry size. escapements on Quesnel and colonized. Let us not forget about Shuswap Lakes. other benefits, too, from the nutrient Discussion delivery to the shoreline vegetation Recent escapements to Shuswap right on up to the birds and bears. It and Quesnel lakes have been the is almost impossible to calculate highest or amongst the highest ever IN A NUTSHELL: A SUMMARY these types of benefits, especially observed. The decomposing DISCUSSION OF THE when we consider that virtually no carcasses from these escapements AFOREMENTIONED TECHNICAL baseline data exists (i.e. has the have returned significant amounts of REPORT number of bears significantly marine derived nutrients (MDN) to declined as a direct result of the South Thompson and Quesnel By Jason Yarmish reductions in numbers of fish to river watersheds. Carcasses in the terminal areas?). Who knows! Shuswap watershed will have First of all, I would like to commend increased nutrient loading to the the Department of Fisheries and This technical report cannot answer lake somewhat but nutrients from Oceans and particularly the staff these types of questions; it is merely carcasses in the Adams River (63% involved for completing this a useful snapshot of what happened of the total in 2002) are mostly important research. Though the as a result of the 2002 diverted downstream by prevailing above technical summary report is escapements. It is the responsibility currents into Little Shuswap Lake not too complicated, I will of managers to ensure that this type and the South Thompson River, summarize it further. of information is not used to prevent where they mostly benefit species large escapements in the future, for other than sockeye. In contrast, In a nutshell, the higher than without successive larger than almost all MDN in the Quesnel average escapements to both the average escapements, we will never system circulates in the lake for Quesnel and Shuswap Lakes did be able to fully predict their impact. some time and will directly affect not result in increased juvenile lake productivity. Our limnological production and the average size of study of Quesnel Lake has shown juvenile sockeye sampled was increased productivity and biomass smaller than in years of lower levels UPCOMING MEETINGS of lower trophic levels as a result of of adult escapement. That seems the recent very high escapements fairly straight forward. But is this March 30, 2004: Tier One Meeting: (Shortreed et al in prep). Increases production ceiling real? Maybe, Location TBA. in phytoplankton and zooplankton maybe not. We need to remember biomass were observed in 2003 but that the higher than average there were no detectable increases escapement in 2002 was just a in juvenile sockeye abundance or single event. And considering size. There are a number of possible sockeye stocks have been reasons for this apparent depressed due to commercial “uncoupling” of fish production from activity for nearly 100 years, it may the increased productivity of lower take many successive large Fraser River Aboriginal Fisheries Secretariat, 274-A Halston Connector Road, Kamloops, BC V2H 1J9 Phone (250) 828-2178 Fax (250) 828-2756 Email [email protected] Website http://www.frafs.ca .

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