aquaculture Flashcards
aquaculture definition
growing aquatic organisms under controlled conditions
2 types of aquaculture
- open - released after certain size
- closed - entire life
3 different levels of aquaculture intensity
- Extensive = species in some sort of pen + natural food
- Semi-intensive = supplements
- Intensive / hyper intensive = Large input of feed + chemicals
**increase env impact as go down
what kind of fish are aquacultured
63% = freshwater species e.g. catfish
29% = marine
8% = brackish
where does the most aquaculture happen
Asia
US = second
what did Naylor et al say about aquaculture
it cannot compensate for declining catches – actually puts more pressure on wild stocks
how much fish caught by fisheries goes into fish meal
40mmt
7 main Impacts of aquaculture
- Wasted biomass
- Competition for food + spawning sites
- Bycatch of larval resources
- Competition for ecosystem goods and services
- Pollution
- Escaped species
- Genetic consequences
explain the Wasted biomass impact of aquaculture
takes more biomass to produce them
- 2-5kg to make a fish meal
explain the Competition for food + spawning sites impact of aquaculture
- No effect of hatchery fish on wild pops (el nino)
- But non el nino they successfully competed for food with wild pops
- Chinook salmon – density dependant interactions of young fish + food
explain the Bycatch of larval resources impact of aquaculture
Can be large bycatch of other larvae – different larval species hang out together
explain the Competition for ecosystem goods and services impact of aquaculture
- Loss of mangroves + saltmarshes to make room for aquaculture -> important nursery habs
- Water usage impacts e.g. trout water has to be continuously replaced
- Ecosystem level interaction - Trophic -> species taken for aquaculture means less food for other species
- Competition for world markets
explain the pollution impact of aquaculture
Pollution due to high conc
- Dissolved o2 - Excess nuts – algal blooms use o2
- visual pollution
explain the Escaped species impact of aquaculture
- Invasive species
- Possible Hybridization: Cultured fish dig fewer nests, lower repro success, males are poorer competitors so females more likely to breed with wild males but offspring will be poorly too (lower repro success), Lower the fitness of a wild individual
-Farmed fish take longer to find streams -> make their nest later -> disturb native nests - Parasites and diseases spread to natives - treating chemicals can also be spread to surrounding env
solutions to Parasites and diseases spreading from aquacultured animals to natives
- Vaccines
- Natural predators for parasites
explain the Genetic consequences impact of aquaculture
- Cultured fish usually have low genetic variation: few individuals start the process, selective pressures, bring fish from other locations (genetics don’t match)
- Cant replace one genetic stock with another
-> cultured fish have lower genetic diversity + genetic makeup than wild pops – cause direct + indirect genetic effects if they meet
whats the direct effects of if native and cultured fish meet
Interbreeding with locals:
- Overwhelming of wild genotypes with foreign alleles
- Modified growth, survival, repro behavior
- Hybrids can replace original pops + decrease diversity
whats the indirect effects of if native and cultured fish meet
Not breeding with locals:
- Habitat destruction
- Wasted repro – try to breed but not successful
- Increased likelihood of extinction
recommendations for solutions to impacts of aquaculture
- Improve formulated feed – less fish meal and more sea oils, farm fish lower on food chain
- Prevent escaped – closed systems, hold farmers accountable
- Minimize genetic impacts – local sources means less impact
- Eliminating pollution – reduce overfeeding, closed systems, reduce chemicals, harvest waste
- Periodic decommisioning
- Culture species appropriate to the conditions – less resources needed to keep animals alive
