Human effect on the ocean Flashcards
(41 cards)
what are marine recources used for?
food
products
materials
recreation
what type of organisms a re harvested from the ocean
finfish (about 90% of worldwide harvest)
shellfish
jellyfish, sea cucumbers, polychaetes and seaweed
how much of the animal protein consumption annually is attributed to seafood?
30%
growth of fisheries industry from 1950’s to present
5 x
worldwide catches still constant
major fishing areas location
near coast over continential shelf
what kind of fish are easiest to catch
demersal species
high _______________ in these areas means more species are present
primary production
what are clupeoid fishes?
Small. plankton-feeding fishes that form huge schools: anchovies, sardines, menhaden, shad, and herrings
caught with purse seines
how are clupeoid fishes used?
eaten directly
fish flour
fish meal
fish oil
what are demersal fish?
cod, haddock, hakes, pollock, whiting
info on the cod fishery of the grand banks
- peaked in the 1960’s then began to decline
- moratorium declared in 1992 to attempt to save the fishery
- closure caused high unemployment
cod is still endangered
Jacks, Mullets, Rockfishes, and Mackerals
- Important in worldwide tonnage
- cheap protein in some parts of the world
In the US, flounders and other _______ are important
flatfish
tuna are
- caught in open water
- highly priced
- caught on long lines or in gillnets
Molluscs are
- squids, cuttlefigh, and octopus important in the far east
- clams, oysters, mussels, scallops and abalones are important worldwide
second most valuable catch after finfish
Crustaceans
- prized worldwide
- command high prices
- shrimp, lobster, crab
are sea life fisheries renewable recources
yes
what is a sustanable yield
the amount that can be caught and just maintain a constant population size
what is the maximum sustainable yield?
the highest catch that can be maintained year after year without affecting the stock
if catches fall despite increased fishing effort, _____________ has occurred.
overfishing
how does habitat destruction affect the productivity of fisheries?
75% of commercially important species use estuarine areas as nursery areas
trawl use is detrimental to demersal species
when is a fishery regarded as ‘collapsed’?
when the numbers fall ot 10% of historic highs
one third are already collapsed
all will be collapsed by 2050 without action taken
why can managing these recourses be difficult?
- maximum sustainable yield is difficult to calculate
- harvested species may compete with other species and fishing pressure may affect competitive balance
-real fisheries are more complex than models - high seas are “common property”
list nine ways to manage a fishery
limit total catch
limiting length of fishing season
limiting areas open for fishing
limiting numbers of boats permitted to fish
limit gear size/type
limit size of fish caught
limit catches per boat
limit fishing methods