Terms of Reference
Assessment of Pacific Sardine, biological sampling of Pacific Herring, and factors influencing the variability in Pacific Herring egg layers and considerations to stock assessment
Pacific Regional Advisory Process
January 18-20, 2011
Nanaimo, British Columbia
Chairperson: Sean MacConnachie
The Centre for Science Advice Pacific (CSAP) Pelagics Standing Committee, along with additional invited participants as required, meet to review information related to assessing pelagic fish stocks. These reviews are based on specific questions outlined in formal Requests for Science Information and Advice. A Regional Advisory Process (RAP) is being planned to review three Research Documents and one Science Advisory Report pertaining to Pacific sardine or Pacific herring in British Columbia waters.
Working Paper 1: Assessment of Pacific sardine in British Columbia waters, with an emphasis on seasonal abundance and migration estimates
Following a RAP conducted in April of 2009, harvest advice in British Columbia (BC) has been based on a 3 year running average of the most recent BC migration rate estimates, a current estimate of the coastwide adult stock biomass (from the US assessment) and applying the US harvest rate ( 15% in recent years). Sardine seasonal migration into BC has been estimated from west coast Vancouver Island (WCVI) midsummer surface trawl surveys. Seasonal abundance and migration estimates based on WCVI trawl survey data have been considered to be minimum estimates because they don’t include other regions of the province where sardines also occur midsummer. Following a meeting with industry in June of 2010, an agreement was made to investigate the feasibility of developing a harvest strategy based entirely on the results of the annual west coast of Vancouver Island trawl survey. A need to investigate the possibility of assessing sardine abundance in other unsurveyed areas of the coast was also identified.
1.1 To review the feasibility of developing a seasonal estimate of sardine biomass in the Canadian zone from the summer research trawl survey data, independent of the US stock assessment.
1.2 To identify issues (e.g. biological and technical, including information gaps) associated with changing from the methodology adopted in April 2009.
1.3 To provide advice on seasonal abundance and/or migration to apply to harvest control rules and setting quotas for the 2011/2012 fishing season
Working Paper 2: Biological sampling of BC herring: Analysis of sampling requirements for characterizing age structure and other biological characteristics of fisheries and spawning populations
Given reductions in resources for data collection following the Larocque court decision, concern has been expressed about the adequacy of ongoing data collection programs. Consequently, there is ongoing interest in exploring the cost-benefits and tradeoffs of varying spatial and temporal sampling coverage versus the precision of parameter estimates. Conclusions and recommendations from several past RAPs have identified this need. Furthermore, these types of evaluations are required in order recognize whether datasets in the time series can be used to distinguish different biological characteristics between regional stock groupings. Despite area closures in 3 of the 5 major regional assessment areas, the biological sampling and spawn survey programs operate annually. However, there is some concern about the adequacy of the biological sampling program in providing information on fish size and age composition of major herring stocks for stock assessment analysis and modelling.
2.1 To review an investigation which explores effects of varying spatial and temporal sampling coverage to adequately characterize fish size and age structure of Pacific Herring stocks in the major assessment areas.
2.2 To determine if existing data can be used to evaluate whether the accuracy and precision of estimates of biological characteristics has changed over time.
2.3 To determine if data trends of biological characteristics are indicative of similarities or differences between stocks in some areas (e.g., Central Coast (CC) subareas 6, 7, and 8).
Working Paper 3: Factors influencing the variability in Pacific herring egg layers and considerations to stock assessment
Although herring spawn data have been collected for over 50 years, a detailed study of factors that influence the number of egg layers deposited has not been conducted. A better understanding of factors governing the density of spawn deposition will provide valuable information on herring reproduction. The assumption that low numbers of egg layers in a specific spawning site is symptomatic of a low spawning biomass should be investigated since this view may be implied by stock assessment sampling and modelling.
Mortality of eggs during spawning has been examined and documented at most major spawning cites, both in the Atlantic and Pacific Ocean. The loss of eggs during spawning has special relevance to Pacific herring stock assessments that rely on a quantitative index of herring spawn as a key component for annual assessments. A particular concern is that as the financial and logistical support for spawn surveys has diminished the timing of the surveys may be relatively later than during earlier surveys. Relatively later assessments of spawning by SCUBA surveys could result in an under-estimate of spawn, hence an underestimate of the spawning biomass. The potential scale of such possible under-estimates is uncertain, but even a relatively small daily loss (~2%) would result in a total loss of over 25% during a 14-day incubation period. A daily loss of 5% would result in total reduction of more than 50% during the same period. Also, there are other uncertainties that affect the estimates of spawn survival, including density dependent survival of eggs, with survival to hatching being lower in very high densities, etc. It is plausible that this is a concern for areas of the BC coast where spawn has tended to concentrate in fewer areas in recent years.
3.1 To review information related to physiological, ecological and behavioural controls that affect Pacific herring spawning behaviour and factors associated with the estimation of the number of egg layers.
3.2 To review information related to factors that affect the estimation of variability in egg layers.
- CSAS Proceedings
- CSAS Science Advisory Report (1), based on Pacific sardine assessment
- CSAS Research Documents (3)
DFO Science Branch
DFO Fisheries and Aquatic Management Branch
Commercial and recreational fishing Interests
First Nations organizations
Cleary, J.S., Schweigert, J.F., Haist, V. 2010. Stock assessment and management advice for the British Columbia herring fishery: 2009 assessment and 2010 forecasts. DFO Can. Sci. Advis. Sec. Res. Doc. 2009/079. vii + 81 p.
DFO. 2009. Proceedings of the Pacific Scientific Advice Review Committee (PSARC) meeting for the assessment of scientific information to estimate Pacific sardine seasonal migration into Canadian waters. DFO Can. Sci. Advis. Sec. Proceed. Ser. 2009/034
DFO. 2009. Proceedings of the Pacific Scientific Advice Review Committee (PSARC) Pelagic Subcommittee Meeting: Stock assessment and management advice for BC herring fishery, 2009 assessment and 2010 forecasts and herring multi-stock analysis; September 2, 2009. DFO Can. Sci. Advis. Sec. Proceed. Ser. 2009/037.
Schweigert, J., McFarlane, G., Hodes, V. 2010. Pacific sardine (Sardinops sagax) biomass and migration rates in British Columbia. DFO Can. Sci. Advis. Sec. Res. Doc. 2009/088.
Participation to CSAS peer review meetings is by invitation only.
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