Fish

1. Fish

2. Characteristics of Fish • Skeleton made of bone • Air (swim) bladder for buoyancy • Mucus to reduce friction, antibacterial agent • Gill cover (operculum) to protect gills and pump water through them (oxygen)

4. Small, thin scales for rapid swimming • Flexible fins (not stiff as in sharks) • Lateral line and other senses, but no ampullae • Ectothermic (cold blooded)

6. Major Groups of North Atlantic Fish • Demersal Fish: Benthic, groundfish (lives on/near the ocean floor) • Cods: cod, haddock, pollock, cusk, hake • Flatfish: flounder (sole), halibut, plaice, turbot

7. Pelagic Fish: open water • Herrings: herring, sardines, shad, smelt, menhaden, gaspereau, capelin • Tuna • Mackerel, Salmon, Eel

8. Deep Sea Fish • Deep sea fish tend to live below 400 m • They have anatomical adaptations to live at these depths such as: large mouths and teeth, modified appendages to serve as lures, and large stomachs • Many are smaller than 6 inches

9. Grenadier: 450-800 m Gulper: 500-3000 m Hatchet: 200-6000 m Swallower: 500-1500 m

10. Lantern: 200-1000 m Scaly dragon: 200-1500 m Tripod: 900-3500 m Viper: 500-2500 m

11. Angler Fish • There are several different species • They usually live between 1500-5000m • Some have a luminous barbel • They use a lure to attract prey • There is one species where the female is 12x the size of the male; he lives as a parasite on her body

13. Fisheries and Fishing Techniques

14. Fisheries Facts • Unlike other natural resources such as oil and gas, fish are a renewable resource • People in coastal regions have been using fish as a major food source for thousands of years • In 1997, the global fishery took 100.8 million tons of fish, crustaceans and molluscs

15. Fishing employs ~15 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 500 species are regularly caught as part of a commercial fishery

16. The largest commercial harvest is herring 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: China, Japan, US, Peru, Russia

17. Commercial Fisheries • Major types of commercial fisheries include: • Groundfish: cod, haddock, hake • Pelagic Fish: sardine, anchovy, herring, mackerel, tuna • Crustaceans: crab, lobster, shrimp, krill • Molluscs: oyster, mussel, clam, squid, scallop

18. Technology Improves Catches • 75% of fishers are cast commercial fleets who find fish using: • Satellite sensors • Aerial photography • Scouting vessels • Sonar • GPS • Huge factory ships follow along to can and freeze the fish as soon as they are caught

19. Fishing Techniques: Trawling (dragging) • The most common method of fishing • A funnel shaped net is towed behind the fishing vessel • Can be towed on the bottom to catch groundfish or at midwater to catch pelagic fish • Bottom dragging is very destructive to the benthic ecosystems

20. Trawling

21. Purse Seine • A net circles a school of fish, the bottom of the net is pulled tight and the fish are hauled aboard

22. Purse Seine

23. Scallop Dragger • Scallops are caught by dredging – a metal frame with a net attached rakes the sandy bottom • This method is also destructive to the benthic environment

24. Scallop Dragger

25. Gillnetting/Driftnetting • A passive fishing method (40-50km long) • A gillnet is a wall of netting set in a straight line equipped with weights at the bottom and floats 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 driftnetting • Must be checked daily

26. Gill Net

27. Long-lining • Long lines of baited hooks 40-50 km long • There are thousands of baited hooks placed in the open ocean, or along the bottom

28. Long-lining

29. Lobster Pots • Lobsters are caught in baited traps with funned shaped openings allowing only one direction of travel – in • They can be single traps, or in groups on a line

30. Lobster Trap

31. Weirs • A passive fishing method • A weir is an enclosure made of nets and poles permanently attached to the bottom • Leader fences direct fish into the circular weir where they will swim in circles until they are removed by the fisher • Herring and sardines are often caught in weirs

32. Weirs

33. Jigging • Squid and cod are often caught by jigging – a line of hooks are continually jerked to lure the fish to bite

34. Fishery Problems: By-catch • Animals that are unintentionally killed when desirable organisms are fished • In many cases, by-catch exceeds the target catch • Thousands of dolphins were caught in tuna nets until regulations changed the net design and ship maneuvers

35. Every method of fishing has this problem • About 20 million tons of unwanted fish may be discarded annually either because regulations prevent capture of these fish or because it is not economical to process them

36. Ghost Fishing • Nets will keep fishing after they have been lost due to storms or negligence • Fish and other organisms will rot in the nets because there is no-one to collect them • Gill nets and long-lining cause the most problems

37. Habitat Destruction • Destroying the ocean floor in the process of dragging nets • The bottom becomes ‘naked’ and it takes a long time to recover – if it does • Trawlers and scallop draggers cause the most damage

38. Declining Fish Populations • Fish stocks worldwide have been declining; many have collapsed due to overfishing • Other reasons for declining numbers are mismanagement, habitat destruction, interference with breeding, and increased ocean pollution

39. Fisheries Management • Scientists study fish stocks to determine estimates of the population count and the reproductive biology of the species • This information allows scientists to estimate the growth rate of the stock and determine the Maximum Sustainable Yield (MSY)

40. Scientists can determine the minimum size of fish to be caught to ensure juveniles are not being harvested • They can also determine times of the year when no fishing should be allowed to protect breeding seasons • Scientists make recommendations to the fisheries managers

41. Fisheries managers set the Total Allowable Catch (TAC) (total tonnage of fish that a fleet can catch) • They also set quotas (total tonnage of fish that a fisher can catch)

42. 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…