Lindstrøm, Planque, Subbey: Multiple patterns of food web dynamics revealed by a minimal non deterministic model S4 EFFECT OF FISHING

Fishing is regarded as the most important direct driver of change in marine ecosystems; it affects structure, function and biodiversity (e.g. Jackson et al. 2001). To investigate possible effects of fishing on the ecosystem properties, we included fishing (export) on pelagic (polar cod and capelin) and demersal fish (cod, haddock, redfish and Greenland halibut) in the model simulations. Extraction by fishing was mimicked by setting export to a fraction of the biomass:

Ci Exporti, t= Biomass i , t (eq. S4.1) Bi

C 2 i where Exporti, t is simulated catch (tonnes km ) of trophospecies i in year t, is the average Bi

catch over biomass fraction of trophospecies i in the study period (1986-2013), Biomassi, t is the simulated biomass of trophospecies i in year t. The total annual catch and biomass of

C pelagic and demersal fish, used to derive i , was taken from Johannesen et al. (2012). The Bi average total catch of pelagic and demersal fish in 1986-2013 was 0.241 and 0.713 million tonnes, respectively, corresponding to approximately 0.15 and 0.45 tonnes km-2 (Barents Sea is 1.6 million km2). The average total biomass of pelagic and demersal fish in 1986-2013 was

C 2.50 and 2.26 million tonnes km-2, thus i was estimated to be 0.060 and 0.198 for pelagic Bi and demersal fish respectively.

The overall conclusion is that fishing did not alter the ecosystem properties noticeably (Figure

S4.1-4.7). The most noticeable change was the change in median biomass of pelagic and demersal fish the last year (2013). For pelagic fish, fishing resulted in a 18.8% increase in

1 Lindstrøm, Planque, Subbey: Multiple patterns of food web dynamics revealed by a minimal non deterministic model median biomass in 2013 whereas for demersal fish the opposite was observed (-6.2%) (Fig.

S.4.1). The average biomass fluxes between the lower trophic level trophospecies (herb. zoopl., omn. zoopl. and benthos) did not change much between the fishing and no-fishing scenarios (Table S4.1). However, there was a notable change for upper trophic; the average annual biomass fluxes of demersal fish and birds declined c. 70-80% and 55%, respectively, when fishing was included whereas the biomass flux to mammals increased by 120-835. The mean trophic level and transfer efficiency of trophospecies were similar between the two fishing scenarios, with the exception of the transfer efficiency of demersal fish, which increased from 11.9% to 14.5% when fishing was included.

REFERENCES

Jackson JBC, Kirby MX, Berger WH, Bjorndal KA, Botsford LW, Bourque BJ, Bradbury

RH, Cooke R, Erlandson J, Estes JA, Hughes TP, Kidwell S, Lange CB, Lenihan HS,

Pandolfi JM, Peterson CH, Steneck RS, Tegner MJ, Warner RR. 2001. Historical

overfishing and the recent collapse of coastal ecosystems. Science 293: 629-637.

Johannesen E, Ingvaldsen RB, Bogstad B, Dalpadado P, Eriksen E, Gjøsæter H, Knutsen T,

Skern-Mauritzen M, Stiansen JE. 2012. Changes in Barents Sea ecosystem state,

1970–2009: climate fluctuations, human impact, and trophic interactions. ICES J Mar

Sci 69:880-889.

2 Lindstrøm, Planque, Subbey: Multiple patterns of food web dynamics revealed by a minimal non deterministic model

Table S4.1. Average biomass fluxes (t.km-2.y-1) between trophospecies over all simulations in the period 1986-2013 with and without fishing.

The flux values in the non-fishing scenario are given in parenthesis. Increases an decreases in biomass fluxes in the fishing scenarios are highlighted in bold and italics respectively.

Trophopspecies Phytoplankton Herb. zoopl. Omn. zoopl. Benthos Pelagic fish Demersal fish Mammals Birds Phytoplankton 396.0 (370.0) 128.9 (141.4) 222.0 (224.3) Herb. zoopl. 94.7 (86.3) 54.2 (59.1) Omn. zoopl. 29.7 (36.1) 3.8 (13.3) 13.1 (1.4) 0.7 (1.6) Benthos 5.6 (29.6) Pelagic fish 4.2 (15.7) 11.9 (1.3) 0.8 (1.9) Demersal fish 3.3 (1.5) Mammals Birds

3 Lindstrøm, Planque, Subbey: Multiple patterns of food web dynamics revealed by a minimal non deterministic model Table S4.2. Mean trophic level and transfer efficiency of seven trophospecies in the

Barents Sea NDND model with and without fishing of pelagic and demersal fish. The

TE and TL estimates are based upon 1000 simulation of 28 year trajectories.

Cannibalistic flows were excluded when estimating the TE’s.

Trophospecies Trophic level Transfer efficiency No Fishing Fishing No Fishing Fishing Herbivorous zooplankton 2 28.1 28.4 Omnivorous zooplankton 3.3 3.3 5.6 5.8 Benthos 2.5 2.6 1.2 1.2 Pelagic fish 4.0 3.9 22.7 22.4 Demersal 4.4 4.4 13.4 16.3 Mammals 4.7 4.7 - - Birds 4.6 4.5 - -

4 Lindstrøm, Planque, Subbey: Multiple patterns of food web dynamics revealed by a minimal non deterministic model

Figure S4.1. Biomass time series of herbivorous and omnivorous zooplankton, benthos, pelagic and demersal fishes, mammals and birds with (blue) and without (red) fishing. The blue and red area denotes the 90% simulation envelopes and the solid blue and red lines denote the median of 1000 biomass simulations. The horizontal hatched blue lines mark the refuge biomasses and the two tilted hatched blue lines denote the lower and upper inertia boundaries. The dashed black lines denote three random simulations.

5 Lindstrøm, Planque, Subbey: Multiple patterns of food web dynamics revealed by a minimal non deterministic model

Figure S4.2. Biomasses distribution (log-scale) of herbivorous and omnivorous zooplankton, benthos, pelagic and demersal fishes, mammals and birds (from 1000 simulations of 28 y) with (blue) and without (red) fishing. Verical dotted blue lines show the refuge biomass for each trophospecies.

6 Lindstrøm, Planque, Subbey: Multiple patterns of food web dynamics revealed by a minimal non deterministic model

Figure S4.3. Growth rate versus biomass for herbivorous and omnivorous zooplankton, benthos, pelagic and demersal fishes, mammals and birds with (blue) and without (red) fishing. The blue and red areas corresponds to 90% simulation envelopes and the solid blue and red lines denote the median of 1000 simulations.

7 Lindstrøm, Planque, Subbey: Multiple patterns of food web dynamics revealed by a minimal non deterministic model

Figure S4.4. Correlations, calculated on 15 y centered sliding windows, between trophic groups (herbivorous and omnivorous zooplankton, pelagic and demersal fish) in empirical and simulated data with (F) and and without (NF) fishing. The boxes and error bars of the boxes correspond to 50% and 95% confidence intervals of the modelled data, respectively, the horisontal solid black lines indicate the median. HZP, OZP, PEL and DEM denotes herbivorous zooplankton, omnivorous zooplankton, pelagic and demersal fish, repectively.

8 Lindstrøm, Planque, Subbey: Multiple patterns of food web dynamics revealed by a minimal non deterministic model

Figure S4.5. Food web stability (upper left panel) and synchrony (upper right panel) with (blue) and without (red) fishing. The blue and red areas corresponds to 90% simulation envelopes and the solid blue and red lines denote the median of 1000 simulations. The area (lower left panel) display 1000 simulated 14-year stability-synchronicity correlations with and without fishing. The solid lines show the mean stability-synchronicty correlations of simulated data.

9 Lindstrøm, Planque, Subbey: Multiple patterns of food web dynamics revealed by a minimal non deterministic model

Figure S4.6. Four consumer-resource functional responses with (blue) and without (red) fishing): phytoplanton-omnivorous zooplankton, omnivorous zooplankton-pelagics, pelagics-demersals and pelagic-mammals. The blue and red areas correspond to 90% simulation envelopes and the solid lines denote the median of 1000 simulations. The blue tilted and horizontal hatched lines denotes the 1:1 (prey consumption = available prey) and satiation (consumption = satiation) constraints, respectively.

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