Investigating coastal ecosystem structure and dynamics using Ecopath/Ecosim ecosystem models and stable isotope data Torstein Pedersen Einar M. Nilssen Silje Ramsvatn, PhD student Trond Ivarjord, vit. Ass. Fredrikke Museæus, tech. Marianne Nilsen, IRIS Lyne Morissette, ISMER, Canada Anita Maurstad, TMU Håvard Fause, master student Ina Kolsum, master student Christer Michalsen, master student Geir Helge Systad, NINA
Background Main objective: which biotic and abiotic factors affect dynamics and structure of coastal ecosystems in northern areas? Is it possible to advocate management regimes that enhance fishery yield, resilience, resistance and biodiversity? Use models that integrate data from classical sampling methods and stable isotope data?
Comparative ecosystem approach; local (Sørfjord vs Ullsfjord), regional, intercontinental scale General large decline in costal cod after 1995 Cascade effects of decline in cod? Ullsfjord warmer and more diverse than Sørfjord Reference ecosystem for king crab effect studies
Barents Sea Ullsfjord & Sørfjord Norwegian Sea Russia Sweden Finland Norway Ullsfjord, a deep, outer and relatively warm fjord (400 km 2 ), and Sørfjord which is shallower and colder (55 km 2 ) Ullsfjord has higher biodiversity
Mass-balance approach Ecological groups (n = 40 in Ullsfjord) Input data are Biomass, P/B, Q/B, Ecotrophic efficiency (need 3 of 4), catches and diet Diet data input are essential Ecopath -> Ecosim -> Ecospace 6 Combine with 5
Unique approach; uses Ecopath-model structure as framework for strategic sampling of groups that are necessary and important to estimate ecosystem model
Structure in Ullsfjord 40 group model, new groups shown in bold, multistanza groups in colour Gr. No. Gr. No. 1 Mammals 21 Heterotrophic nanoflagellates birds & mammals (5) 2 Pisciivore benthic bird 22 Schypomedusae 3 Pelag diving birds 23 Chaetognaths 4 Surface feeding birds 24 Other shrimps 5 Benthic invertebrate f. birds 25 Pelagic shrimps 6 Large cod 26 Other large zooplankton 7 Small cod 27 Large crustacea 8 Large saithe 28 Predatory benthos 9 Small saithe 29 Detrivore polychaetes 10 Large haddock 30 Small benthic crustacea Fish (10) 11 Small haddock 31 Small molluscs 12 Small gadoids 32 Large bivalves 13 Large other fish 33 Detrivore echinoderms 14 Small other fish 34 Herbivore echinoids 15 Small pelagic fish 35 Other benthic invertebrates 16 Herring 36 Bacteria 17 Small krill 37 Phytoplankton 18 Large krill 38 Macroalgae zooplankton/ crustaceans 19 Small zooplankton 39 Discard and offal 20 Microzooplankton 40 Detritus zooplankton/ cr.nekton (10) benthos (9)
Field/Survey Literature data Commercial catch data Diet analysis
Large sampling effort, challenge to sample all groups and diets representatively
How to represent; top-predators, fish and pelagic groups (WP1), benthic invertebrate groups (WP2)? How to assess and incorporate data from stable isotopes into an Ecopath model (WP3)? How to evaluate effects of trophic control mechanisms and exploitation regimes using Ecopath/Ecosim modelling (WP4)?
Stable isotopes (SI) Trophic level (TL) Carbon δ 13 C= 13 C / 12 C Primary source of carbon
SI can be used to investigate ontogenetic diet shifts Haddock less than 20 cm in length feed pelagic and then change to a more benthic signature/diet at larger size Ullsfjord Small haddock (< 20 cm)
How to compare Ecopath models with diet data input from gut content analysis (GCA) and stable isotopes (SI)? Use MIXSIR, a bayesian source mixing model, to estimate diet prey proportions for a predator from the SI of the predator, SI of potential prey groups and trophic enrichment factors for delta13c and delta15n. Uses individual data.
GCA Ecopath Comparison of trophic levels estimated directly from SI data and Ecopath model based on stomach/literature data input 1:1 line regression SI data
SI Ecopath Comparison of trophic levels directly from SI data and Ecopath model based stable isotope data diet input Trophic level increased with new diet data SI data
Fish species Invertebrate bentic predators Invertebrate benthos Detrivore echinoderms
whiting Trophic redundancy long rough dab (fish with length 20-40 cm) witch haddock
Fish species Invertebrate bentic predators Invertebrate benthos Detrivore echinoderms
Conclusions SI SI can be used to estimate diet input to Ecopath models More local data can be used SI can be also used to improve diet data from benthic invertebrates, need sufficient diversity of groups
Comparative Ecosystem approach
Group Fish and shrimp Pelagic shrimp Shrimps Herring Small pelagic fish Small other fis Large other fis Small gadoids Small haddock Large haddock Small saithe Large saithe Small cod Sørfjord Ullsfjord Large cod 0.00 0.05 0.10 0.15 0.20 0.25 0.30 Biomass (g C m -2 )
Group Group Benthic invertebrate groups Biomass P/B Other benthic i Other benthic i Herbivore echin Herbivore echin Detrivore echin Detrivore echin Large bivalves Small molluscs Large bivalves Small molluscs Sørfjord Ullsfjord Small benthic c Detrivore polyc Predatory benth Large crustacea Sørfjord Ullsfjord Small benthic c Detrivore polyc Predatory benth Large crustacea 0.0 1.0 2.0 3.0 4.0 5.0 Biomass (g C m -2 ) 0.0 0.5 1.0 1.5 2.0 P/B (per year)
Regional comparison Mammals Seabird Norwegian Sea/Barents Sea Sørfjord Ullsfjord North Sea Cod Haddock Saithe Prawns Small gadoids Small pelagic fishes and herring 0.00 0.00 0.01 0.10 1.00 10.00 Biomass g C m -2
Intercontinental: Sørfjord versus Northern Gulf of St Lawrence, Canada Who are the main predators? Morissette et al. 2009 In Sørfjord, fishing mortality is minimal, and cod is the dominant predator In the Gulf of St. Lawrence, fishing is 10X higher, and since cod is collapsed, marine mammals became the main predators
Annual catch (tons) Fangst per fartøy (kg per fatøy) Fishery regimes. Annual catches of deep sea shrimp in Ullsfjord and Lyngen (source Råfisklaget) 600 Fangst Ullsfjord 500 Fangst Lyngen 400 300 200 100 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 År