The impact of climate change on fisheries and the ecosystem of the western Scotian shelf, Canada.

Transcription

1 The impact of climate change on fisheries and the ecosystem of the western Scotian shelf, Canada. Alida Bundy, Sylvie Guénette, Julio N. Araújo Fisheries and Oceans Canada Funded by ACCASP (DFO Aquatic Climate Change Adaptation Services Program)

2 OVERALL OBJECTIVE Explore the possible effects of climate change on the marine ecosystem of the Western Scotian shelf and its fisheries for the next 50 years using Output from climate change models Ecopath with Ecosim Future fishing scenarios A lot of assumptions Concentrate on yield, exploited species biomass and ecosystem structure next 20 year - potential effects of short term climate variability next 50 years - potential effects of longer term climate change. Guenette S, Araújo JN and A Bundy, Exploring the potential effects of climate change on the Western Scotian Shelf ecosystem, Canada. Journal of Marine Systems 134 (2014)

3 kg/m3 * 10^-7 Climate projections from NOAA model (ESM2M) Temperature Oxygen ph METHOD Zooplankton size structure Temperature : Large zooplankton S zooplankton Primary production projections Chlorophyll optimistic pessimistic Physiological effects on fish and invertebrates scope of growth Driver Food web model (Ecopath with Ecosim) 5 Toothed cetaceans Seals Sharks Large pelagic S Hake 31+ D piscvores Sea birds Cod 4-6 Cod 7+ Halibut Halibut Dogfish Whales Cod 1-3 Pollock Redfish <22 S Hake Skates Redfish 49+ Halibut 22+ Pollock <46 <49 S Hake <25 Herring Herring 4+ <4 Squids L sculpin Cod <1 L benthivores L sculpin 25+ <25 Mackerel Skates A <49 Small-medium benthivores plaice 26+ Other pelagic A plaice Haddock <26 Haddock <3 3+ Mesopelagic Gelatinous zoop Large crabs Flounders 3 Lobster Macrozoop Other molluscs Small crabs Shrimps Microzoop Mesozoop Sessile benthic groups 2 Bivalves Worms Scallop Other arthropoda Echinoderms Meiofauna Microflora Detritus Discards Phytoplankton Predictions of future yield and biomass (20 and 50 yrs)

4 CLIMATE PROJECTIONS Based on NOAA GCM models In absence of downscaled model for WSS (Scotian Shelf) Earth System Model ESM2M (Dunne et al., 2012) developed by NOAA-GFDL Selected two scenarios: RCP 2.6 (optimistic) RCP 8.5 (pessimistic) Extracted predictions for grid cells in the study area

5 mg/l kg/m3 * 10^ Celsius ph PREDICTIONS FOR THE FUTURE Temperature ph optimistic pessimistic Oxygen Chlorophyll a

6 ZOOPLANKTON Relative biomass Relative biomass As temperature increases, proportion of macrozooplankton decreases Macrozooplankton Mesozooplankton optimistic pessimistic Phytoplankton size predicted to decrease with increasing temperature (Moran et al. 2010) Smaller phytoplankton size is predicted to result in lower copepod production (Hilligsøe et al., 2011) as predation limited by size preference. Assumed zooplankton size structure linearly related to temp (Ainsworth et al. 2011; Bouman et al. 2003)

7 TEMPERATURE EFFECT ON DISTRIBUTION IGNORED Western Scotian Shelf close to centre of the geographic distribution of most exploited species in the region No changes in the last 40 years except in the south of New England coast (Pinsky 2013) Observed contraction in distribution seem linked to exploitation and decr. biomass (Shackell et al 2005) Exploration using climate envelope predict loss of habitat at extreme north and south (Van Guelpen et al. 2007) Lack of time for small-scale analysis

8 EFFECT ON PHYSIOLOGY FISH AND SOME INVERTEBRATES

9 growth index TEMPERATURE Assumed changes in bottom temperature similar to SST Focus on the likely effect of increased water temperature on scope for growth Based on hypotheses and lab studies about physiology Temperature: preferred temperature window as a proxy for optimum temperature Based on cod model Two scenarios: 1. Pessimistic CC + Conservative temp. 2. Optimistic CC + Optimistic temp. Applied to fish and a few invertebrates conservative optimistic Temperature (Celsius)

10 ACIDIFICATION based on literature for taxa, families, etc. qualitative vulnerability: grouped FGs into high or low 2 scenarios of decrease in growth for each 0.3 decr ph: Scenarios Vulnerability Pessimistic Optimistic High 30% 15% Low 10% 5% Method following Cheung et al. 2011

11 OXYGEN Studies on effect of oxygen on cod (Claireaux et al 2000). Vulnerability: using literature review (Vaquer-Sunyer and Duarte 2008) Sub-lethal effects on Scotian Shelf Combination: % decrease in growth for each 1% O 2 saturation loss

12 MODELLING THE EFFECTS OF CLIMATE CHANGE WITH FF IN EWE Seals Fishery FF (Temp, O2, ph) FF (ZP) FF (PP) Cod Production Herring Zooplankton Phytoplankton Consumption FFs based on ESM2M projections for the next 50 years Temperature, ph and oxygen assumed to affect the scope of growth - modelled with forcing function (FF) affecting search rates for food (feeding success, therefore growth)

13 SIMULATIONS Sequence Optimistic scenario Pessimistic scenario Effects included 1 1optPP 1pesPP primary productivity (PP) 2 2optT 2pesT PP + temperature (T) 3 3optpH 3pespH PP +T + ph 4 4optO2 4pesO2 PP +T + ph + oxygen (O 2 ) 5 5optzoo 5peszoo PP +T + ph + O 2 + zooplankton size structure Fishing Scenarios: Fishing mortality held constant at value for % decrease in fishing mortality ALL results were compared to a status quo run (PP constant and no other climate effects): B end (10 yr av) / B status quo(10 yr av)

14 RESULTS

15 BIOMASS OF FUNCTIONAL GROUPS mm+birds Linverts Biomass opt zoo O2 ph Temp PP PP always largest effect ZP size structure 2 nd. ph important for inverts 5peszoo worse (ex MM+birds) Total B decreased by % from status quo HighTL Lfish Spel Groundfish Total biom O2 zoo Temp ph PP B end / B status quo peszoo 4pesO2 3pespH 2pesT 1pesPP 5optzoo 4optO2 3optpH 2optT 1optPP

16 CATCH RESULTS Catches predicted to decrease by 5% 48% Greater for large invertebrates and small pelagics Total catch decrease by %

17 DECREASE FISHING BY HALF Biomass of a few species would increase relative to SQ: Cod (35%), American plaice (300%), Halibut (Hippoglossus hippoglossus, 44 52%), and Pollock (5 11%) Catches of a few species would increase relative to SQ: Cod (12-73%) American plaice (60%) Lobster (25-35%)

18 CONCLUSIONS

19 CONCLUSIONS 1 st time that effects of climate change have been modelled in an ecosystem context in eastern Canada Climate change projected to result in decreased biomass and catch of virtually all groups and species modelled in the system due to decrease in productivity. We may not be able to detect changes in biomass over the next years, but fisheries catches will clearly be impacted Degree of impact varies Most sensitive to changes in primary production, then ZP size structure Large invertebrates sensitive to increasing ph Effects of climate change are mediated by species interactions (predator/prey) Underscores the importance of examining the effects of climate change in an ecosystem context, accounting for predator and prey interactions. Reduction in fishing mortality is projected to lessen the effects of climate change

20 CAVEATS Uncertainty is high Physiology and projected changes Not known for all species Based on literature Requires empirical analysis Downscaled climate change scenarios EwE Model structure and parameterisation Fishing scenarios modelled Tried to capture bounds of uncertainty with optimistic and pessimistic scenarios Overall effect of climatic change may be underestimated given that all effects were not applied to all groups for lack of basic information. In light of more recent climate projections: Present simulations represent predictions for a 1ºC An optimistic scenario The new pessimistic scenario 4ºC increase.

21 NEXT STEPS Develop spatial model (EcoSpace) to include change in available habitat and extend model to whole Scotian Shelf Use more specific downscaled GCM for the Scotian Shelf Explicitly include CC effects on juveniles, which would likely be more vulnerable to changes in environmental conditions Include seasonal effects and phenology Work with FAM to explore future scenarios, and a formal trade-off analysis

22 THANKS TO: Fisheries and Oceans Canada Aquatic Climate Change Adaptation Services Program (ACCASP) Carie Hoover, Dave Preikshot, William Cheung, Cam Ainsworth, Ian Perry DFO colleagues