Post on 19-Jan-2016
Fish
Characteristics of Fish
• Skeleton made of ________
• _______________ bladder for buoyancy
• Mucus to reduce friction, ______________________________
• ____________ (operculum) to protect gills and pump water through them (oxygen)
• Small, thin scales for rapid swimming
• ___________ fins (not stiff as in sharks)
• Lateral line and other senses, but no ______________
• ______________ (cold blooded)
Major Groups of North Atlantic Fish
• Demersal Fish:____________________
________________________________–________: cod, haddock, pollock,
cusk, hake
–_________: flounder (sole), halibut, plaice, turbot
• Pelagic Fish: __________________
– ___________: herring, sardines, shad, smelt, menhaden, gaspereau, capelin
– _________
– Mackerel, Salmon, Eel
Deep Sea Fish
• Deep sea fish tend to live below ____ m
• They have anatomical adaptations to live at these depths such as: ________
________________________________________________________________
• Many are smaller than ___ inches
Grenadier: 450-800 m Gulper: 500-3000 m
Hatchet: 200-6000 m Swallower: 500-1500 m
Lantern: 200-1000 m Scaly dragon: 200-1500 m
Viper: 500-2500 m Tripod: 900-3500 m
Angler Fish
• There are several different species
• They usually live between _________m
• Some have a ____________
• They use a ______ to attract prey
• There is one species where the female is ___x the size of the male; he lives as a ___________ on her body
Fisheries and Fishing Techniques
Fisheries Facts
• Unlike other natural resources such as oil and gas, fish are a ______________
• People in coastal regions have been using fish as a major food source for thousands of years
• In 1997, the global fishery took ________ million tons of fish, crustaceans and molluscs
• Fishing employs ~___ million people worldwide, but is the most dangerous job in the US (155 deaths:100 000 fishers)
• Of the thousands of species of marine organisms in the ocean, only about _____ species are regularly caught as part of a commercial fishery
• The largest commercial harvest is _________ and relatives (sardines, anchovies) which comprise 20% of the worldwide catch each year
• The top five fish harvesters in order from greatest to least are:
Commercial Fisheries
• Major types of commercial fisheries include:– ______________: cod, haddock, hake– ______________: sardine, anchovy, herring,
mackerel, tuna– ______________: crab, lobster, shrimp, krill– ______________: oyster, mussel, clam,
squid, scallop
Technology Improves Catches
• ____% of fishers are cast commercial fleets who find fish using:
→
→
→
→
→• Huge factory ships follow along to can and
freeze the fish as soon as they are caught
Fishing Techniques: Trawling (dragging)
• The most common method of fishing
• A _______________ net is towed behind the fishing vessel
• Can be towed on the _______________ to catch groundfish or at _____________ to catch pelagic fish
• Bottom dragging is very ____________ to the benthic ecosystems
Trawling
Purse Seine
• A net _________________________
__________________________________________________________________________________________
Purse Seine
Scallop Dragger
• Scallops are caught by __________ – a metal frame with a net attached rakes the sandy bottom
• This method is also destructive to the benthic environment
Scallop Dragger
Gillnetting/Driftnetting
• A passive fishing method (_______ km long)
• A gillnet is a wall of netting set in a straight line equipped with ________ at the bottom and _________ at the top
• Fish swim through the net and are caught when their gills become entangled in the net
• If the nets are allowed to drift freely, the method is called ____________
• Must be checked ____________
Gill Net
Long-lining
• Long lines of ____________ hooks 40-50 km long
• There are ____________ of baited hooks placed in the open ocean, or along the bottom
Long-lining
Lobster Pots
• Lobsters are caught in baited traps with funned shaped openings allowing only ______ direction of travel – in
• They can be single traps, or in groups on a line
Lobster Trap
Weirs
• A passive fishing method
• A weir is an enclosure made of nets and poles _____________ attached to the bottom
• Leader fences direct fish into the circular weir where they will ______________ until they are removed by the fisher
• ___________ and ____________ are often caught in weirs
Weirs
Jigging
• Squid and cod are often caught by jigging – a line of hooks are continually jerked to lure the fish to bite
Fishery Problems: By-catch
• Animals that are _______________ killed when desirable organisms are fished
• In many cases, _____________________
___________________________
• Thousands of _____________ were caught in tuna nets until regulations changed the net design and ship maneuvers
• Every method of fishing has this problem
• About ______________________ of unwanted fish may be discarded annually either because regulations prevent capture of these fish or because it is not ___________________ to process them
Ghost Fishing
• Nets will keep fishing after they have been lost due to _________________________
• Fish and other organisms will rot in the nets because there is no-one to collect them
• _________________________________ cause the most problems
Habitat Destruction
• Destroying the ocean floor in the process of dragging nets
• The bottom becomes ‘_________’ and it takes a long time to recover – if it does
• ______________ and _________________ cause the most damage
Declining Fish Populations
• Fish stocks worldwide have been declining; many have collapsed due to _________________
• Other reasons for declining numbers are: ________________________________________________________________________________________________________________________________________
Fisheries Management
• Scientists study fish stocks to determine estimates of the _________________ and the reproductive biology of the species
• This information allows scientists to estimate the _______________________ and determine the ____________________________________________________________________
• Scientists can determine the minimum size of fish to be caught to ensure _____________ are not being harvested
• They can also determine times of the year when no fishing should be allowed to __________________________________
• Scientists make ____________________ to the fisheries managers
• Fisheries managers set the ___________
___________________________ (total tonnage of fish that a fleet can catch)
• They also set ________ (total tonnage of fish that a fisher can catch)
Fisheries Mismanagement
• Poor science leads to poor estimates
• Managers disregard scientists recommendations
• Fishers do not obey quotas
• Other factors (not taken into consideration) may deplete the population: foreign fishers, weather, pollution etc…