Monitoring Climate Change in Oceanic Fisheries

1. Monitoring Impacts of Climate Change on Oceanic Fisheries(Filling Important Information Gaps)John HamptonOceanic Fisheries Programme, SPC

2. Monitoring Climate Change in Oceanic Fisheries • Impacts on target species (tunas) • E.g., recruitment, natural mortality, growth, movement, reproduction • Impacts on the underlying ecosystem • Pelagic food web, trophic structure, biodiversity • Impacts on the fisheries • Distribution and performance (CPUE), size composition, species composition • Subject of ongoing programmes of data collection and stock assessment

3. 1. Impacts on Tuna High-resolution modelling of skipjack population, with catches (circles) overlain • With a good understanding of the way that ocean environment interacts with tuna biology, we can predict responses of tuna stocks and fisheries through simulations forced by climate change model scenarios • SEAPODYM model is a model of high spatial resolution, that may be suitable as a monitoring and forecasting tool • Can assimilate environmental, biological and fisheries data in near-real time

4. Early Results of Simulations Skipjack Bigeye

5. SEAPODYM-Based CC Modelling • Phase 1 (1 year, in progress, funded by Aus DCCEE) • Revise skipjack and bigeye simulations using new forcing data • Extend to yellowfin and South Pacific albacore • Run simulations for A2 and B1 scenarios • Phase 2 (3 years, funding being sought) • Further develop simulations, e.g. to include effects of ocean acidity • Apply a ‘plausible ensemble’ of IPCC-class simulations to bound uncertainty in tuna responses • Sub-regional/national applications using down-sized data

6. Future Climate Change Impacts • Use the SEAPODYM framework to monitor in near-real-time, and to predict into the future • The reliability of model estimates dependent on: • Accurate high-resolution output of models of physical/biological oceanography conditioned on/validated by extensive observations • Accurate high-resolution fisheries data (collected as part of the regular OFP fishery monitoring work programme) • Fishery-independent data that are directly informative on the processes liable to be subject to change – movements, natural mortality, growth

7. Tuna Tagging Bigeye Tuna Skipjack Tuna Tuna tagging can provide direct data on tuna biological process for use in CC monitoring and prediction

8. CC Monitoring Proposal 1 Regular (annual) structured tagging surveys to monitor dynamic processes (movement, growth, etc) likely to be impacted by CC Surveys would provide empirical indicators of change Data assimilated into SEAPODYM models would enhance predictive capabilities Currently have funding (USD 3 million) for 3 x 3 month annual tag release cruises in PNG Additional funding to extend that work into other areas of the Western and Central Pacific

9. 2. Changes in the Underlying Ecosystem Climate change impacts on target tuna species are fairly readily observable However, changes at lower trophic levels may also occur, and if observable, could provide an “early warning system” for pending large-scale changes in the tropical pelagic ecosystem Observing lower trophic levels (baitfish, squid, small crustaceans, etc) directly is logistically difficult and costly

10. Tuna Stomach Contents Sampling as an Observational Window

11. Sampling of Top Predator Stomachs

12. CC Monitoring Proposal 2 Establish baseline data set from existing data Design structured sampling programme utilizing national & regional longline observer programmes Conduct ongoing sampling and analysis of tuna and other top predator stomachs as a means of observing changes in mid-trophic levels Incorporate these data along with catch estimates for target species and bycatch into ecosystem models Potential to also consider new acoustic monitoring data from buoys and ships of opportunity