Fisheries + Aquaculture Flashcards
What types of species make up the most of fisheries catches?
small pelagic fish (i.e anchovies, sardines, herring) and large finfish (tuna, billfishes etc)
What were the three most caught species of fish in 2018?
- anchoveta
- pollock
- skipjack tuna
What proportion of total catches and consumption do artisinal fisheries make up?
25% of total catches
40% of human protein consumption
What is the relationship between wealth and need for food?
countries that have a low GPA rely extensively on subsistence fishing for bulk of protein intake
What are value-effort mismatches in fisheries?
operating costs»_space; landing value, so subsidies are required to keep fishery in operation
Briefly describe the history of the Chilean loco (abalone)
- exports to Asian markets increased after the 70s, and value peaked in 1980
- fishery collapsed in late 80s, closed in 1990 but reopened mid 90s well below peak harvest
Briefly describe the history of the California white abalone
- peak harvests in the 70s decimated population, had little to no harvests
- fishery closed late 90s and listed as endangered in 2001
Briefly describe the history of the Galapagos sea cucumber
catches decreased over time but market value per individual increased
Briefly describe the history of the Atlantic cod
- pre 1980: most of landings were from international fleets
- 1980: EEZ placed, Canadian landings increased
- 1990s: fishery crashed and closed
What are the trends of boom-bust fisheries?
- abundance decreases after development
- fleet size increases after development then plateaus
- catch increases after development then crashes at collapse (oversaturation of boats)
- profit decreases after development and is lowest after collapse (operations > profit)
What is discounting?
prioritizing current value over potentially higher value in the future
i.e accepting $10 now over potentially getting $15 in 2 years
Why do fishers discount?
- some assume that by leaving the fish alone, the returns might not be as good as the present
- risk of another fisher taking advantage of whatever you pass up
What are the 4 types of active gear covered in class?
- purse seine
- beam trawl
- otter trawl
- scallop dredge
What are different methods of static fishing?
- trap/pots (mainly crustacean farming)
- gillnet fishing (highly selective by changing size of nets)
- longlines (selective with hook size but high risk of bycatch)
- pole and line (labour intensive but very low chance of bycatch)
Who predominantly fishes artisanally and what methods do they use?
- women and children who fish to feed households
- gleaning (hand picking), spears/harpoons/throw nets, blast fishing, muro-ami
What effects do blast fishing/muro-ami have on ecosystems?
blast fishing
- detonations stun all nearby fish who float to surface
- destroys large parts of habitat
muro-ami
- stones oscillate and smash habitat to scare fish out to catch
- destroys coral
What is the perfect (but unrealistic) hypothetical fish to harvest?
one that has an early but large maturation, that produces many offspring that are also large, and has a long reproductive lifespan
What population effects can fishing have?
- lowers abundance
- lowers mean age and mean size
- reduces fecundity (targets large reproductive females = smaller reproductive females remain, fecundity decreases)
- skews OSR of population (i.e target larger individuals = targets more males, more females left behind)
- can quickly change population regimes that are very difficult to correct (i.e reducing age of maturation)
What were the main findings from the experiment involving silverside fish and size selection?
trial involving selecting (fishing) large fish = favoured individuals with slower growth rate
trial involving selecting (fishing) small fish = favoured individuals with a faster growth rate
What community effects can fisheries have?
- local extinctions (extirpations)
- affect the ecosystem’s diversity and structure (biomass of larger species, removal of higher trophic species)
What part of the world has the most bottom trawling?
Europe
What effects do bottom contact trawling have on the seabed?
- reduced roughness (removes larger sediment/structures)
- resuspends sediment (can release contaminants, reduce nutrient and oxygen availability)
- change in sediment
Explain why trawls have less of an impact on coral in warm water versus cold water
- warm water is often clearer and shallower, higher visibility might avoid destruction of some corals
- nets/hand fishing/pots mostly used in these areas vs trawls
How does bottom contact trawling affect epifaunal and infaunal life?
epifaunal
- reduces surface habitat complexity
- damages animals
infaunal
- lower abundance/richness in impacted gravel based areas
- very slow recovery time post-trawl
What is one benefit fisheries provide for ecosystems?
discards provide energy subsidies for scavengers/seabirds
What components make up bycatch?
valuable non-target species, over quota of target species and non valuable species
What type of fishing creates the most bycatch?
trawl fishing
Which fishery creates the most bycatch?
shrimp fishery (5kg discard/1kg target)
What animals are most often caught in bycatch?
salmon, marine mammals and halibut
Where and how are seabirds most caught by bycatch?
- longlines and gillnets
- hot spots around Australia, southern South America, Eastern coast of southern Africa
How can seabird bycatch be reduced?
- bird scaring lines
- funnels over lines to hide them above water
- use frozen bait to sink faster
- fish at night
Why should fishermen want to reduce bird bycatch?
it would reduce bait lost as well as reduce time needed to rebait lines
Where and how are reptiles most caught by bycatch?
- longlines, gillnets and trawls
- hotspots off eastern USA, western Central America, southern Europe and southeastern South America
How can reptile bycatch be reduced?
- trawl excluders to allow escape
- reduce tow duration
Why should fishermen want to reduce reptile bycatch?
snakes are highly venomous, and turtles can damage nets, bring in bad publicity and inspire boycotts
Where and how are mammals most caught by bycatch?
- longlines, gillnets
- hotspots around Europe, PNW of USA, northwestern South America
Why should fishermen want to reduce mammal bycatch?
damages nets, brings in bad publicity and boycotts, prevents access to certain markets by affiliation
How can mammal bycatch be reduced?
- reduce fishing effort
- trawl excluders for escape
- acoustic pingers for echolocating mammals to identify
- set bycatch quotas
- change fishing practices (i.e more distance from mammals)
What part of the world makes up the bulk of aquacultures?
China + Asia
What type of animals make up most of marine, brackish and freshwater aquacultures?
marine = fish
brackish = crustaceans (prawns)
freshwater = molluscs (oysters)
Define intensive, semi intensive and extensive aquaculture systems
extensive = low human involvement post-stocking, naturally supplied by nutrients
i.e oyster farms, subsistence tilapia farming
semi-intensive = incorporated into other production types, fed by fertilizers, organic waste and manure
i.e tilapia/carp farms
intensive = high human involvement, use of artificial feed and use of antibiotics for disease prevention
i.e salmon farming
What two pathogens are found in shrimp farms?
white spot syndrome (Asian farms) and Taura syndrome (American farms)
Why are shrimp farms especially harmful to the environment?
- nutrient buildup in farms can be released into mangroves or ocean water
- mangrove forests destroyed to create shrimp farms
- saltwater from irrigation can pollute freshwater ecosystems
- threatens natural shrimp populations
What impacts does salmon farming have in BC?
- can create hypoxic/anoxic conditions
- can cause accumulation in metals
- escaped fish can compete/reproduce with native fish
- can spread disease to native fish
What solutions are available to solve issues with BC salmon farms?
- fallowing (respite periods where fisheries can clean facilities)
- reduce stock density and transfers
- place farms away from migration routes
- switch zinc to a bioavailable form
What phenotypic changes can fisheries cause?
shorter and smaller individuals, paler skin and shorter fins, lower reproductive output
What were some key findings from the paper by McLenachan (2009)?
- historical photos suggest a loss in large species of trophy fish
- unfished communities had higher overall biomass and more large predators
