Fisheries Flashcards
Location restrictions:
closure of fishing activities in specific area protects fish that are vulnerable to catching pressure. Like spawning grounds.
season restrictions:
set times of the year fishing is allowed or not allowed. Closures are usually set to protect vulnerable times of the year like spawning.
How is optimal sustainable yield different than maximum sustainable yield?
optimal sustainable yield considers other economic, social or ecological constraints. Better safe than sorry
what are three methods of commercial fisheries?
- purse seine: they let out the net so that it surrounds the school of fish and then close the top closed and then they pull the bag into the boat. 2. deep water trawl: big impact on ocean life 3. long line fishing: long line with baited hooks. One of the more ethical practices because it is really targeted.
what are 6 other population assessment tools?
- Gill netting: long sections of mesh net that can select for specific age classes or size of fish by using different mesh sizes. 2. Seine nets: walla of netting with float line and lead line used to encircle fish. Fish are funneled into a deep pocked in the middle of the net. 3. Hoop nets: cyclindrical net suspended by hoops and connected using funnel shaped netting. effective for bottom feeders if baited. 4. Trap nets: a net consisting of 2 wings and one lead which fish hit and follow into the collection basket. 5. Hook and line: - trotline: concsits of heavy line with bati hooks attached - line and lure: useful for procuring live specimens and providing info about population structure and abundance. 6. electrofishing: power source used to induce electrical current into water to stun fish.
why is maximum sustainable yield not the best?
because it ignores: 1. age structure 2. age to reproduction 3. age to natural mortality 4. selection of age/size class by fisherman
tools for mark recapture
- Fin cli-s , quick and easy but little info 2. T-bars/Floy tags- attach to fin or body muscle, quick, last longer than first one and offer more info, but can affect fish. 3. Passive integrated transponder (PIT) tags- injected beneath the skin of fish and uses external energy to relay a uniq code.
what is the purpose of mark-recapture?
to estimate the size of a population for animals that would be unreasonable to count.
fish are –% of the global protein intake
17
global fishing industry valued at ~————
240 billion
what is the idea behind maximum sustainable yield?
the idea is that harvest rates should be around where growth rates are the highest.
creel survey?
informal way to estimate the population. how many hours did you fish? how many fish did you catch? how many trips did you take this year? what species did you catch?
estimated that around –% of the worlds population partake in fishing
18
estimated that ———— fish are caught annualy recretioanlly. 1/8th of the commerical fisheries harvest
50 billion
subsistence fishing:
non-commercial, local fisheries that supploy food for their families and communities but are unable to see for profit. Thought to have negligible impact on fish abundance, but highly variable by system and understudied.
marine ecosystems are highly impacted through what 3 effects?
- Bycatch- economically worthless species caught using indiscriminate fishing methods 2. Overharvesting: removing too many idnviduals from the population so they are no longer able to sustain the population and it crashes 3. Ecosystem disruption: either direct damage through bottom trawling or indirect through removing an entire tropical level from the food web
