Conservation & Management of Fishes I. The Need for Conservation & Management I. The need for conservation & management II. Causes of decline & extinction III. Solutions A. Extinction rates of animals are at an all time high: 1000x the long-term average (10-100x over previous maxima) B. Populations of many fishes are at their lowest densities ever e.g., most large predatory species are ~10% of virgin levels Extinctions of Fishes 20% of the world s freshwater fishes are extinct or in serious decline (Moyle and Leidy 1992) 250 of 450 species in Lake Victoria are thought to be extinct (but no known extinctions of marine fishes in modern times) Modern Extinctions of Fishes (IUCN 2007) Order Extinct Extinct in wild Total Class: Actinopterygii ACIPENSERIFORMES 0 0 0 ATHERINIFORMES 0 0 0 BATRACHOIDIFORMES 0 0 0 BELONIFORMES 0 0 0 CHARACIFORMES 0 0 0 CLUPEIFORMES 0 0 0 CYPRINIFORMES 20 2 22 CYPRINODONTIFORMES 12 5 17 GADIFORMES 0 0 0 GASTEROSTEIFORMES 0 0 0 GONORYNCHIFORMES 0 0 0 LOPHIIFORMES 0 0 0 MUGILIFORMES 0 0 0 OPHIDIIFORMES 0 0 0 OSTEOGLOSSIFORMES 0 0 0 PERCIFORMES 40 6 46 PERCOPSIFORMES 0 0 0 PLEURONECTIFORMES 0 0 0 SALMONIFORMES 6 0 6 SCORPAENIFORMES 1 0 1 SILURIFORMES 1 0 1 SYNBRANCHIFORMES 0 0 0 TETRAODONTIFORMES 0 0 0 Total (Actinopterygii) 80 13 93 All other classes of fishes: 0 0 0 Why are these numbers so much lower than other estimates? *all are freshwater or anadromous (none marine) Extinct Fishes pupfish - C. alvarezi blackfin cisco Utah lake sculpin cichlids in Lake Victoria beluga sturgeon (Adriatic stock) Endangered Fishes in the US (US EPA) 139 species, subspecies, or stocks ( ESU s ) e.g., 9 steelhead stocks (Oncorhynchus mykiss) e.g., 10 chinook salmon stocks (Oncorhynchus tshawytscha) 138 are freshwater (105) or anadromous (32 salmonids & sturgeons) 1 marine species (smalltooth sawfish, Pristis pectinata) Other estimates: 106 major Salmonid stocks extinct, 214 more at risk in Washington, Oregon, California, & Idaho (Nehlsen et al. 1991) 1
Endangered Fishes steelhead trout - southern California stock Devil s hole pupfish Depletion of fish populations: Fisheries value: ~ $100 billion / yr worldwide annual catch: ~ 200 trillion pounds Chinook salmon - Sacramento winter run totoaba lake sturgeon smalltooth sawfish Overfishing: widespread and fast -- fished populations are typically reduced to 10% of their original density within 2 decades Myers & Worm 2003 1889 1902 An example: the California sardine fishery first sardine cannery -- caught with beach seines sardine cannery in Monterey -- caught with gill nets & purse seines 1905 first lampara net, these then dominate the fishery 1913 reduction begins (fish meal & oil) -- drives industry 1918 150,000,000 pounds harvested 1920 s DFG Biologists warn of overfishing ( CPUE, age, distance to fishing grounds) 1930 s purse seines return & dominate by 1940 s 1936 1,500,000,000 pound harvested (record) 1938 F&G Commission reports unmistakable signs of depletion & imperative need to reduce the harvest 1939 F&G Commission sacked by Governor There is every reason to believe that the problem is near at hand. Our fishery has advanced farther than we have perhaps dreamed they have perhaps gone too far. W.F. Thompson, DFG biologist, 1922 It is absurd for anyone who really knows the facts to say that you can deplete the supply of sardines in the Pacific Ocean. Knut Hovden, major Monterey sardine canner The California sardine fishery, cont. 1942 new F&G Commission reports no reason to be concerned over the possibility of the extermination of the sardine by the fishermen 1940 s PDO: ocean temperatures cool 1940 s Federal Government takes over fishery during WWII late 1940 s game over in Monterey 1950 s southern stock crashes 1960 s game over in southern California mid 1970 s PDO: ocean temperatures warm 1980 s small fishery returns present small fishery still sustainable 2
California sardine landings Effects of Overfishing 1. Growth Overfishing 2. Recruitment Overfishing 3. Ecosystem Overfishing 4. Other Effects Overfishing relatively recent for most species, coinciding with advent new technologies Then 1. Growth Overfishing average size of individuals declines, by... selective removal of large fish or shortened lifespan Now associated changes younger average & maximum ages decreased reproductive output skewed sex ratios Growth overfishing of Nassau groupers in Jamaica (Thompson & Munro 1978) Overfishing affects sex ratio of red hind in Jamaica (Thompson & Munro 1983) Lightly fished area Heavily fished area Epinephelus guttatus Sex ratios in red hind Pedro Bank Port Royal Cays Lightly fished Heavily fished male: female 1 : 2.8 1 : 5.6 3
2. Recruitment Overfishing adult biomass reduced to point where recruitment declines 3. Ecosystem Overfishing decline in fish population alters community & ecosystem structure -- removal of apex predators: fishing down food webs (Pauly) -- causes trophic cascades: humans cod (top predators) in the Gulf of Maine lobsters (and many other changes) Fishing has altered trophic structure of Hawaiian coral reefs 4. Other Effects of Fishing Behavioral changes Genetic changes Habitat destruction Friedlander & DeMartini 2002 Behavioral changes Hanauma Bay, Hawaii Genetic changes Chinook salmon over 60 years: 2 yr decrease in age at maturity 50% decline in size at maturity Fish genetically programmed to mature later don t ever get to reproduce!... a cumulative genetic effect of removing fish of larger than average size (Ricker 1981) 4
Habitat destruction II. Causes of Population Declines & Extinction A. Habitat Loss / Modification B. Introductions C. Pollution D. Global Climate Change E. Fisheries Habitat Loss / Modification Water Diversion & Dams -- example: the Colorado river humpback chub Habitat destruction Land reclamation Blast fishing Modification Dams Channelization Deforestation Water Diversion Colorado pikeminnow Totuaba Pacific Salmonids Introductions forestry practices (e.g., clearcutting) causes siltation of spawning bed (redds) dams Predation Competition Disease / Parasitism Hybridization fishing rainbow trout Tilapia 200+ species of cichlids extinct in Lake Victoria salmon escape from farm pens largemouth bass mosquitofish 5
Pollution acute chronic Global Climate Change coral bleaching reduction of productivity shifting of habitable zones pole-ward DDT acid rain Fishing direct mortality (Overharvesting) incidental catch (Bycatch) habitat destruction (e.g., trawling) III. Solutions A. Ultimate: stop human population growth & reduce use of natural resources B. Proximate: 1. Effective Fisheries Management 2. Conservation a. habitat preservation b. reserves (e.g., MPAs) 3. Habitat Restoration 4. Captive Breeding? Fish populations rebound when fishing is halted goliath grouper in Florida & the gulf states giant sea bass in California striped bass on the east coast of the US white seabass in California But we still need to eat, right? Fisheries Management Two general types open access -- fishery open to everyone restricted access -- fishery open only to certain people 6
Open Access 1. Size Limits 2. Gear restrictions and prohibitions 3. Fishery-wide quotas 4. Closed seasons or areas -- Seasons (often protect spawning periods) -- Marine Protected Areas (MPAs) Restricted Access 1. License Limitations 2. Territorial Use Rights in Fisheries (TURFs) 3. Individual Fisherman s Quota or Transferable Quota (IFQ or ITQ) Fisheries Management Traditional goal of fisheries management: achieve maximum sustainable yield (MSY) Fisheries Theory assumes density-dependence is strong i.e., logistic growth with a carrying capacity MSY = greatest harvest that can be sustained without causing the fishery to crash density or biomass K MSY (at 1/2 K) time Population growth rate vs. density in a species with logistic growth Population growth rate (dn/dt) 140 120 100 80 60 40 20 0 MSY = 500 K = 1000 0 100 200 300 400 500 600 700 800 900 1000 Population density (N) Maximum sustainable yield (MSY) = greatest harvest that can be sustained without causing the fishery to crash This concept has failed as a management tool 70-90% of the world s fisheries are fully or overexploited fully exploited = can t take any more fishing without crashing overexploited = fishery has crashed Why? must estimate K correctly, or fishery may crash 7
A reason why the MSY concept has failed: ignores economic principles Reasons why the MSY concept has failed: ignores economic principles no safety margins assumptions about biology wrong A single 489 lb. bluefin sold for $1,780,000 poor data used in models Sustainable Fisheries require Prudent Predation Optimal (real) predators forage below MSY: natural mortality for many finfishes is < 10% MSY targets 50% actual fishing mortality is often 70%-90%! Optimal (real) predators switch prey in response to population fluctuations (or cannibalize): fisheries should switch prey types when certain species become rare State of the World s Fisheries: It ain t pretty! 70-90% of worlds fisheries are fully or overexploited (source: UN FAO) stock abundance of most major fisheries < 10% of virgin stock Atlantic cod commercially extinct Are there sustainable fisheries? Some of the problems with traditional fisheries management supply and demand Solutions: What can you do? know what kind of fish you re buying and how it is harvested or raised overcapitalization non-convertibility multiple users multispecies fisheries Tragedy of the commons William Forster Lloyd 1833; Garrett Hardin 1968 incidental catch fisheries models inaccurate poor data on fish populations unenforceable regulations politics Roughy are too ugly to eat 8
Biological characteristics that predispose species to overfishing Nassau grouper spawning aggregation slow growth (e.g., rockfishes) late maturity (e.g., sturgeon, sharks, rays) long lifespan (e.g., rockfishes, sturgeon, giant sea bass, snappers) restricted movements (local depletion) (most reef fishes) low abundance (e.g., top-level predators) (e.g., sharks) spawning aggregations (e.g., groupers & snappers) Conservation Marine Protected Areas Marine Protected Areas (MPAs) Strong points whole-ecosystem approach simplifies management (less knowledge of biology necessary) simplifies enforcement (if accepted by the community) may generate revenue via eco-tourism provides control areas for studying human impacts provides insurance against failure of other methods excellent for conservation Weak points does not control overall rate of mortality may require huge closures ineffective for highly mobile species may be less efficient than traditional methods fisheries benefits unproven disliked by many fishermen (lack of community buy in ) 9