NAFO WGRP – 3rd set of ToRs

ToR 1:  Explore and conduct evaluation of underlying assumptions of protocols used to estimate total realized egg production of selected marine species and stocks

Co-Leaders:  Rick Rideout (DFO, Canada) and Rosario Dominguez (CSIC, Spain)

Several marine laboratories in the North Atlantic have initiated routine fecundity estimation for key fish stocks. This information is being used to (i) help improve the estimation of stock reproductive potential (ii) understand population productivity and (iii) predict stock recovery rates.  However, there is a lack of standarization and calibration of various methods to estimate fecundity among laboratories. For example, some laboratories have only recently initiated the autodiametric method and are developing appropriate calibration curves. On the other hand, observations have been made that indicate atresia and timing of sampling can influence estimates of total egg production.  Techniques to quantify atresia (vitellogenic oocyte resorption) will be developed and evaluated in this ToR. This will involve histological analyses accompanied by computerized image analysis.

Establish Standard Operating Procedures:

–   Provide uniform and standarized procedures for routine fecundity analyses in laboratories using a variety of methods, i.e. autodiametric method, image analysis
–   Evaluate histological techniques for assessment of atresia

Validation of Assumptions:
–   Test assumptions of different fecundity methods (i.e. the autodiametric method) and parameters associated with fecundity estimation
–   Estimate down regulation of fecundity and quantification of atresia and non-annual spawning

ToR 2:  Explore and investigate the potential effects of changes in water temperature and food supply on reproductive success in selected marine species and stocks

Co-Leaders:  Richard McBride (NMFS, USA) and Stylianos Somarakis (HCMR, Greece)

Environmental factors can modify the reproductive potential of fish stocks and thereby influence recruitment.  Annual variations in water temperature and potential increases due to climatic warming will presumably act strongly to influence gonadal development and reproductive success.  Prey resources also vary and influence fish condition which in turn affects reproductive output.  In this ToR, using data on specific stocks and laboratory experiments, the influence of specific abiotic and biotic factors on gonadal development and spawning will be evaluated pending available data.

Abiotic:  Examine changes in water temperature (short and long-term) and their effects on timing and duration of spawning, fecundity, egg size and fertilization success
Biotic:  Assess variation in prey resource type and abundance and their effects on egg production and gamete quality

ToR 3:  Undertake appraisal of methods to improve fish stock assessments and fishery management advice that incorporate new biological data for highly exploited and closed fisheries

Co-Leaders:  Joanne Morgan (DFO, Canada) and Loretta O’Brien (NMFS, USA)

The depressed and age-altered state of many marine fish stocks has led to reduced landings and in some instances fishery closures.  New biological data associated with these altered states will be used to forecast recruitment and improve the accuracy of stock assessment advice.    Building on information from previous WG ToRs, the intrinsic rate of population increase will be utilized to assess the timeframe for selected stocks to recover under various fishing and environmental conditions.

Recruitment prediction: Improve prediction of incoming year class size and develop new stock-recruitment models and biological reference points based on better estimates of stock reproductive potential.  This includes testing whether more complex indices of reproductive potential result in better estimates of recruitment and limit reference points.  Develop scenarios which model population reproductive responses to extrinsic factor data developed in ToR 2.

Stock recovery: Evaluate the intrinsic rate of increase of selected stocks under differing conditions of reproductive potential and levels of fishing mortality to aid in the development of reopening criteria.  Estimate recovery time for specific stocks to achieve target biomass levels.
Egg production methods can estimate spawner biomass and/or stock numbers independently of commercial fisheries data.  Improved information on stock reproductive potential is improving the accuracy of these methods.  The daily egg production method is being explored to evaluate adult stock size for determinate spawning species in the Baltic and North Seas.  For this ToR a meta analysis/review of this topic will be conducted to inform Scientific Council of advances in this area.