And Low-Trophic-Level (LTL) Species/Taxa Represented in the Ecosystem Models

Appendix A. Supplementary data

Table A1. High-trophic-level (HTL) and low-trophic-level (LTL) species/taxa represented in the ecosystem models. Ecosystem Modelled HLT group species/taxa Modelled LTL group species/taxa Ecosystem model Atlantic bonito, Bluefish, Atlantic Horse mackerel, Shad, Sprat, Black Sea mackerel, Whiting, Turbot, Red Ecopath with Ecosim Anchovy mullet, Spiny dogfish Mustelus mustelus, Merluccius Sardina pilchardus, Sardinella merlucciu, Octopus vulgaris, aurita, Engraulis encrasicolus, Gulf of Gabes OSMOSE Melicertus kerathurus, Metapenaeus Diplodus annularisPagellus monoceros, Trachurus trachurus, erythrinus Dab, Whiting, Sole, Gurnard, Plaice, Sprat, Sandeel, Norway Pout, North Sea Size Spectrum Haddock, Cod, Saithe Herring Shrimps, Crabs, Norway lobster, Benthic invertebrates, Benthic Benthopelagic cephalopods, Conger cephalopods, Mullets, Flatfishes, eel, Anglerfish, Demersal fishes (3), Poor cod, Juvenile hake, Blue Adult hake, Demersal sharks, South Catalan Sea whiting, Demersal fishes (1), Ecopath with Ecosim Atlantic bonito, Swordfish and Tuna, Demersal fishes (2), Benthopelagic Loggerhead turtles, Audouin's gull, fishes, European anchovy, Sardine Other sea birds, Dolphins adults, Other small pelagic fishes, Horse mackerel, Mackerel Shallow Demersals, Flathead, Pink Ling, Trevalla, Gummy Shark, Small Mackerel, Myctophids, Red Bait, Southeastern Australian Pelagic Tuna, Demersal Shark, Atlantis Squid, Krill Dogfish, Grenadier, Pelagic Shark, Gulper Shark, Shallow Piscivores Chub mackerel, Adult Horse mackerel, Snoek, Other large pelagics, Merluccius capensis, Anchovy, Sardine, Redeye, Other Merluccius paradoxus, small pelagics, Juvenile Horse Southern Benguela Ecopath with Ecosim Pelagicdemersals, Benthicdemersals, mackerel, Mesopelagics, Pelagic Chondrichthyes, Benthic Cephalopods, Chondrichthyes, Apex Chondrichthyes Walleye pollock, Pacific cod, Euphausiids, Shrimp, Pacific West coast Canada Lingcod, Spiny dogfish, Spotted OSMOSE herring, ratfish, Harbour seal Flatfish, Other small fish, Mackerel, Cod mature, Haddock mature, Horse mackerel, Blue whiting, Whiting mature, Pollock, Gurnards, Herring, Norway pout, Sandeel, Western Scotland Ecopath with Ecosim Monkfish, Rays,Sharks, Large Sprat, Nephrops, Lobster, Edible demersals, crab, Crustaceans, Cephalopod, Scallops

Sardine Herring Scad Complex, King mackerel, Amberjacks, Red Anchovies and Silversides, Coastal West Florida Shelf grouper, Gag grouper, Red OSMOSE omnivores, Reef carnivores, Reef snapper, omnivores, Shrimps, Large crabs

Sharks, Cod, Silver Hake, Halibut, Haddock young, Longhorn sculpin, Pollock, Demerdal piscivores, Large Herring, Other pelagic, Mackerel, Western Scotian Shelf benthivores, Skates, Dogfish, Mesopelagic, Small-medium Ecopath with Ecosim Redfish, American plaice, benthivores, Squids, Lobster, Flounders, Haddock adult Crabs, Shrimps, Scallop

Table A2. Descriptions of the ecosystem modelling frameworks applied in the study.

Atlantis Ecopath with Ecosim OSMOSE Size Spectrum Size-structured Individual- Mass-balance model of Whole ecosystem model based model of fish Multispecies model marine foodwebs that Summary from hydrodynamic community dynamics with describing the flux accounts for the flow of description conditions to foodweb and coupling with hydrodynamic of biomass along biomass between trophic human users and biogeochemical models size classes groups. (end-to-end model). Includes age structure and Ecosim is a dynamic model major ecological processes Trophic interactions describing the predator- The whole life cycle of the such as full life history are size-based and prey interactions from species is modelled closure, gape-limited the dynamics of Key features primary producers to top (migration, food-dependent predation, habitats, multiple focus fish predators. Can include growth, reproduction and movement, biogeochemical species is multiple stanzas representing mortality) in space and time. nutrient cycling and a range modelled. different age classes. of effort allocation options. Individual biomass and Currency Nitrogen Biomass Biomass numbers 2D, regular grid. Vertical Spatial distribution of fish is handled 2D, polygons None None structure through a matrix of accessibility. Depends on configuration, Needs time series of Life history traits, predator but usually extensive abundance/biomass and/or to prey size ratios, fish Life history traits, Parameter- parameterisation is fishing effort/mortality and spatial distribution data. predator to prey ization required. Also needs ideally environmental drivers Data needs for model size ratios physical drivers and initial in Ecosim to fit the model to calibration: biomass indices system state. data. and commercial catch data No age structure, "Multistanza" age classes for Fish age is tracked; but each Age structure Vertebrates: 10 age classes some species/functional discretization depends on species/functional groups time step. group is fully size structured Function repsonse is an Functional response is not Functional emergent property of imposed. Predation emerges Holling Type I,II,III, others Holling Type II response Ecosim, based on the from individual interactions "Foraging Arena". and maximum ingestion rate. Intrinsic population growth rate for non-stanza groups; Based on fecundity and Ricker, Beverton, fixed recruitment emerges from Beverton-Holt Reproduction spawning stock biomass, number per adult, others fecundity and feeding stock-recruitment recruitment emerges behaviour for multi-stanza groups. Movement/ Foraging and seasonal No movement in the case Foraging and seasonal No movement migration migration studies here migration Spatial: Fleets' catch, effort, Fleets' catch, effort, or Fishing effort, size Fishing Fishing mortality rates or fishing mortality rates fishing mortality rates selectivity

Fig. A1 Cumulative shifts (in R2 units) in response to levels of primary productivity (multiplier of phytoplankton biomass) in ten marine ecosystems with first column for indicators B/C (biomass to fisheries catch ratio), Pred (proportion of predatory fish), IVI (mean intrinsic vulnerability), and Lifesp (mean life span); second column for TLc (mean trophic level TL of catch), TLcVar (mean TL of catch with variable TL), MTI (marine trophic index), and TLco (mean TL of fish community surveyed); and third column for B_all (biomass of all species), B_htl (biomass of high-trophic-level species), B_all (biomass of low-trophic-level species), B_H2A (the ratio of B_htl to B_all), B_L2A (the ratio of B_ltl to B_all), and B_L2H (the ratio of B_ltl to B_htl).

Fig. A2 Threshold shifts in the values of four indicators indicators (B/C: biomass to fisheries catch ratio, Pred: proportion of predatory fish, IVI: mean intrinsic vulnerability, and Lifesp: mean life span) along the gradient of fishing pressure under random change in primary productivity of standard deviation = 0.1. The dashed line indicates where the ratio of the density of split importance to the density of observed fishing pressure is 1; peaks above the dashed line suggest threshold values for the fishing pressure. Missing plots indicate failed convergence of the gradient forest model.

Fig. A3 Threshold shifts in the values of four trophic level (TL) based indicators (TLc: mean TL of catch, TLcVar: mean TL of catch with variable TL, MTI: marine trophic index, and TLco: mean TL of fish community surveyed) along the gradient of fishing pressure under randome change in primary productivity of standard deviation = 0.1.

Fig. A4 Threshold shifts in the values of six biomass-based indicators (B_all: biomass of all species, B_htl: biomass of high-trophic-level species, B_all: biomass of low-trophic-level species, B_H2A: the ratio of B_htl to B_all, B_L2A: the ratio of B_ltl to B_all, and B_L2H: the ratio of B_ltl to B_htl) along the gradient of fishing pressure under random change in primary productivity of standard deviation = 0.1. The dashed line indicates where the ratio of the density of split importance to the density of observed fishing pressure is 1; peaks above the dashed line suggest threshold values for the fishing pressure. Missing plots indicate failed convergence of the gradient forest model.

Fig. A5 Threshold shifts in the values of four indicators indicators (B/C: biomass to fisheries catch ratio, Pred: proportion of predatory fish, IVI: mean intrinsic vulnerability, and Lifesp: mean life span) along the gradient of fishing pressure under random change in primary productivity of standard deviation = 0.3. The dashed line indicates where the ratio of the density of split importance to the density of observed fishing pressure is 1; peaks above the dashed line suggest threshold values for the fishing pressure. Missing plots indicate failed convergence of the gradient forest model.

Fig. A6 Threshold shifts in the values of four trophic level (TL) based indicators (TLc: mean TL of catch, TLcVar: mean TL of catch with variable TL, MTI: marine trophic index, and TLco: mean TL of fish community surveyed) along the gradient of fishing pressure under random change in primary productivity of standard deviation = 0.3. The dashed line indicates where the ratio of the density of split importance to the density of observed fishing pressure is 1; peaks above the dashed line suggest threshold values for the fishing pressure. Missing plots indicate failed convergence of the gradient forest model.

Fig. A7 Threshold shifts in the values of six biomass-based indicators (B_all: biomass of all species, B_htl: biomass of high-trophic-level species, B_all: biomass of low-trophic-level species, B_H2A: the ratio of B_htl to B_all, B_L2A: the ratio of B_ltl to B_all, and B_L2H: the ratio of B_ltl to B_htl) along the gradient of fishing pressure under random change in primary productivity of standard deviation = 0.3. The dashed line indicates where the ratio of the density of split importance to the density of observed fishing pressure is 1; peaks above the dashed line suggest threshold values for the fishing pressure. Missing plots indicate failed convergence of the gradient forest model.