FISHERIES PT.1 Flashcards
5 reasons fish are taken from the ocean
- Food – people get 20% protein from fishes – 27% of protein = from fish
- Natural products – oil, swim bladders, medicinals
- Curios / aquaria
- Sport – catch + release
- Fish meal
what is fish meal
nutrient rich feed ingredient made from fish – used in the diets of domestic animals + as a fertilizer
How much have we taken from the ocean
- number of fishing vessels has doubled since the 1970s - but catch rates have only increased by 30% before declining
- The ocean yields 100–120 mmt of seafood per year
- We have reached / exceeded the sustainable limit of fisheries biomass extraction
5 places fisheries efforts concentrated
Nontropical shelves = most
Tropical shelves
Upwelling zones
Coastal and coral
Open oceans
5 countries that fish outside their EEZ’s
China
Spain
Taiwan
Japan
South korea
what percent of the oceans are fished
> 55%
8 ways the fish are collected
- Purse sein nets – net connected to ship - pelagic fish – get some bycatch
- Drift nets – let go and collected at a later point
- Gill nets
- Long lines
- Trawls – benthic + demersal fish
- Hook and line
- Pots
- Traps
what kind of fish are fished
- 35,800 fish species contribute to fisheries
- 58% = marine
- 1% = diadromous
3 main taxonomic groups of fisheries
- Jawless – agnatha e.g. hagfish, lampreys
- Class chondrichtyes, elasmobranch – cartilagenous fishes e.g. sharks, skates, rays
- Bony fishes, perciformes – 725,000 – e.g. salmon, tuna, sturgeons (caviar)
characteristics of the most fished species
- small-bodied - big ones have been already fished out
- low in food chain
- schooling species
- 8 are pelagic
what are the Most fished species used as
fish meal
4 popular Non-fish fisheries
- Whales – most are protected but some countries still fish
- Sea otters
- Stellar sea cow extinct – manatees and dugongs now protected
- Sea turtles
Invertebrates
- Corals - jewelery
- Bivalves e.g. oysters, clams
- Crustaceans e.g. crab, shrimp
- Urchins
how much of the overall take does recreational fishing account for
4% – but a very big portion of the take for individual species
lethal and sublethal effects of recreational fishing (catch and release)
- increased mortality
- Sublethal effects: alter social behaviour, impaired reproduction, physiological stress, reduced activity, increased vulnerability to predation
why are Nociceptors
Sneddon et al
pain-like receptor organ in fish – 6x more sensitive to stimuli than ones in human skin
what percent of global fish are overexploited
70%
what is overfishing
fishing mortality above threshold
what is overfished
biomass below threshold
what is rebuilt
has stock rebuilding plan, in year x of x year plan
where does the US fall in the world for global takes
5th
9 main Characteristics of species vulnerable to depletion
Slow pop turnover
Low reproductive potential
Low capacity for recovery
Restricted range – geo or with depth
Small pop sizes
High trophic positions
Reduced larval dispersal
Large body size
Long life span
explain the slow pop turnover characteristic for species vulnerable to depletion
Long life span
Slow growth rates
Long natural mortality
*take long time to grow, mature and reproduce
explain the Low reproductive potential characteristic for species vulnerable to depletion
Low fecundity
Single lifetime reproductive event
Long time between successful repro
Late sexual maturity
Gender change (male -> female)
Density dependent repro
explain the Low capacity for recovery characteristic for species vulnerable to depletion
All number 1 and 2
Limited dispersal
Density dependent effects on settlement or recruitment
