Lecture 8 Scientific Approaches in Marine Resource Management But first – catch up from last class Next class reading: Artelle et al 2013

World “dependence on” (use of) fish 15% of world protein supply One billion people use fish as main source of animal protein Use of fish is higher in coastal areas 95 million tons harvested directly from salt and fresh water each year Most used directly for food, but increasingly for animals feeds etc [Food and Agriculture Organisation of the United Nations (2002)]

Major depletion of world fish stocks A recent paper in PLOS Biology reviews some of the current problems with the fishing industry and fish stocks around the world [Gewin (2004)] Key points cited in the paper include: 28% of global [fish] stocks are significantly depleted or overexploited, and 47% are either fully exploited or meet the target “maximum sustainable yields”. Only 24% of global [fish] stocks are either under- or moderately exploited.

Other signs of decline 55 species of marine fish have lost at least part of their geographical range 3 species of marine fish have gone extinct over the past two centuries An analysis of 230 fish populations showed an 83% reduction from known historic levels. But ‘known historic levels’ often underestimates true historic population [Hutchings and Reynolds (2004)]

Another sign…CPUE Decline Catch per unit Effort Myers & Worm, 2003, Nature

Other Fisheries Consequences?... Shrinkage mean fish lengths in a population shrink reproduce at younger ages and smaller sizes McClenachan 2009 Conservation Biology

BC SALMON SHRINKAGE Ricker 1981 Ricker 1981

Fishing Down the Food Web [Pauly et al. (1998)] Large predatory fish biomass today is estimated to be only about 10% of pre-industrial levels (sharks, skates, rays, and marlin) [Myers and Worm (2003)]

Historical Overfishing Pleistocene, Holocene, Historical, Ecological time periods Aboriginal, colonial, global – cultural periods of exploitation Ecological changes due to overfishing are strikingly similar across ecosystems despite the obvious differences in detail Jackson et al. (2001)

Pollution, eutrophication, habitat destruction, disease outbreaks, invasions of introduced species, and human-induced climate change all come much later than overfishing in the standard sequence of historical events Overfishing may often be a necessary precondition for eutrophication, outbreaks of disease, or species introductions Jackson et al. (2001)

-provide the missing baseline for future restoration efforts Fisheries management based on recent data only may be misleading…earliest data on surveys on fish stocks may already be on over exploited populations Suggest using historical data measured in centuries rather than decades to: -provide the missing baseline for future restoration efforts -raise the possibility that many more marine ecosystems may be vulnerable to collapse in the near future With a few exceptions, most species that are ecologically extinct probably survive in sufficient numbers for successful restoration. In stark contrast with the state of many terrestrial ecosystems, where many or most large animals are already extinct Jackson et al. (2001)

Recovery from Exploitation Various studies suggest that some fish do not recover rapidly from overexploitation Research for 90 fish stocks revealed that 15 years after collapse, 40% of gadids (haddock, cod, and flatfishes) had little, if any, recovery Only 12% exhibited full recovery All were clupeids (herring and related species) attributable to earlier maturity, reduced vulnerability to incidental exploitation or bycatch, and possibly reduced probability of habitat destruction by fishing gear due to pelagic lifestyle [Hutchings (2000); Hutchings and Reynolds (2004)]

Problems that Prevent Recovery (the “resources”) Inter-specific competition and (natural) predation; reduced abundance of top predators causing a shift in ecosystems that may impact recovery; the ‘Allee effect’ (small population sizes lead to proportionally increased rates of predation, reduced mating success and reduced fertility); [Hutchings and Reynolds (2004)]

Problems that Prevent Recovery (humans) slow response by managers to address depletion; inability to reduce anthropogenic mortality to zero (e.g., by-catch continues); selective harvesting - the largest most successful animals are targeted whereas animals with lower fitness stay in the population. [ Hutchings and Reynolds (2004)] public/user-group perceptions that are unsupported by science that delay or alter the nature of the managerial response  links to Ludwig model

Lessons Commercial species cannot be managed in isolation from the ecosystems that they occupy Humans must be considered part of ecosystems and the biosphere, subject to the same natural laws and benefiting from the same supporting services as other species Uncertainty needs to be incorporated into fisheries management models (i.e. there is a lot that we don’t know)

- Values/Laws later this term One scientist is quoted in Gewin (2004) saying: “…it’s naïve to think that modifying and improving models will necessarily lead to improved natural resource management.” Another stated: “The big mistake is suggesting that you can manage fish stocks….we can only manage human activity.” - Values/Laws later this term

Course Outline Concept Map Science ENVIRONMENT humanity resources

Law of the Sea 1978 (200 mile limit for management) Recognition that the sea’s resources were not inexhaustible. The need to have tools for agreeing international standards for management limits Canada’s Pacific EEZ Introduction of Mathematical Modelling - the beginning of setting in stone the direction of research. CCIRA 4 Nation’s Marine Territories

Decline in Field Work: It’s expensive. Biology is time consuming Decline in Field Work: It’s expensive. Biology is time consuming. Computer modelling is cheap and fast. Photo by John Dunn

The essential guide to fisheries management science To understand why fisheries is managed the way it is, you need to know about one number... often called the TAC (total allowable catch) (or similar). What we allow ourselves to take so – in theory – we can maximize/optimize the amount we take over the long run

How (most) Fisheries Science Sees Marine Resources + - Humanity’s piece

Stock-recruitment modeling fishery (or 1 year) (individuals or biomass) Recruits – those that come back to the Stock (biomass or # individuals, often females) S/R relationship used to determine how much of “stock” to exploit and how much to allow “escape” to recruit later OVER LONG TERM Female fish produce many, many eggs, giving populations the capacity to increase rapidly after exploitation (if conditions are right for the survival of the young). Rapid reproductive rate allows humans potential to exploit at a “maximum sustainable yield” rate, assuming and anticipating recovery.

Stock-recruitment modeling fishery (or 1 year) (individuals or biomass) Recruits – those that come back to the Stock (biomass or # individuals, often females) replacement line is where stock = recruits. Recruits above this line are considered "in excess" of that required to maintain the population S/R usually domed shaped (under “Ricker” model”); recruits maxed at medium stock densities The TAC = the amount over and above C

Each year is a data point in the model (The real world – salmon S/R data and models from BC Each year is a data point in the model Use the past to predict the future response to your current fishing (anticipate how salmon will recover in the next year after exploitation) “All models are wrong. Try to use the least wrong one”

The problems with fisheries modeling, and especially S/R Theoretical problems (i.e. within the theory) – do not account for changing environmental conditions Cohen Commission: Judge Cohen spent three years and $26 million looking for answers around the collapse of a Fraser River sockeye salmon run. 1.4 million vs 10 million in 2009 30 vs 10 million in 2010 No “smoking gun” contamination/development on river conditions for juveniles at sea climate change

The problems with fisheries modeling, and especially S/R Practical problems - Despite being very common still, these models have a remarkably poor track record. Many enormous fish stocks have been carefully managed into near-extinction by the use of these models (eg. Atlantic cod, the anchovy, the salmon). “Other” problems? Food webs ignored (management is single species)  EBFM coming People (i.e., diff user groups) not considered Uncertainty is often not incorporated into decision-making