18 Food From the Sea

1. 18 Food From the Sea Notes for Marine Biology: Function, Biodiversity, Ecology By Jeffrey S. Levinton ©Jeffrey S. Levinton 2001

2. Fisheries • Relatively primitive form of food acquisition - hunting and gathering • Fishery is a renewable resource - resource exploitation at certain levels need not deplete the resource • Crucial objective is to develop an appropriate management program to avoid overexploitation

3. Stock - a key concept • Stock - definition • Stock - management unit (nursery, feeding area, political boundaries, fishing limits)

4. Identification of Stocks • Tags - • Biochemical and molecular markers -

5. Gulf Coast bands Atlantic bands Mitochondrial DNA markers used to identify stocks of Striped Bass, Morone saxatilis

6. Crucial Life History Information Needed • Physiological limiting factors • spawning/nursery habitat • feeding areas • Biological information that minimizes unintended mortality during fishing

7. Stock Size • Landings - usual determinant • Fishing effort - f(person-hours fishing, gear used, number of boats) • Catch per unit effort - what is reported

8. Landings of the blue whale, as compared with effort Catch per catcher-day’s work 1931 32 40 47 50 60 1963 Year

9. Fisheries Model • model of population change • Must know life history: the mode of reproduction, the number of young produced, the survivorship, growth periodicity (seasonal), rate of growth)

10. Mortality Recruitment Nursery area Reproduction

11. 30 20 10 0 Frequency 66 103 124 140 Carapace length (mm) Identification of Age Classes by Size: lobster Panuliris ornatus.

12. Model of Fishery Population W = Wt-1- MW t-1 + RW t-1 + GW t-1 W change of mass M mortality proportion R reproduction proportion G growth proportion

13. Stock Recruitment Models • Objective: predict recruitment (the number of newly born that enter and are noticed in the first year class - 0+ ) • Prediction from previous year’s stock • Model premise: density dependence - reproduction declines with increasing density • Therefore: recruitment increases with increasing stock size up to a point, then decreases

14. 120 40 80 0 Density-dependent effects Recruitment 0 400 800 1200 1600 Stock in previous year Stock-recruitment model

15. Maximum Sustainable Yield • Based on idea that a fishery stock will grow at a slower rate over a certain stock size

16. Maximum Sustainable Yield2 • Based on idea that a fishery stock will grow at a slower rate over a certain stock size • Idea is to fish the stock down to the population level where growth is maximal

17. Maximum Sustainable Yield3 • Based on idea that a fishery stock will grow at a slower rate over a certain stock size • Idea is to fish the stock down to the population level where growth is maximal • Leads to management tool to determine fishing pressure

18. Maximum Sustainable Yield4 • Based on idea that a fishery stock will grow at a slower rate over a certain stock size • Idea is to fish the stock down to the population level where growth is maximal • Leads to management tool to determine fishing pressure • Not much evidence that this approach works, even if the theory makes some sense

19. Maximum Sustainable Yield 5 • Based on idea that a fishery stock will grow at a slower rate over a certain stock size • Idea is to fish the stock down to the population level where growth is maximal • Leads to management tool to determine fishing pressure • Not much evidence that this approach works, even if the theory makes some sense • Problem might be that factors other than simple density dependence affect stock size

20. Fishing Techniques • Hooking fishes individually - e.g., long lines with rows of hooks • Entangling fishes in nets - e.g., large drift nets, nets towed below the surface and kept open with wooden boards • Traps - e.g., baited lobster traps kept on bottom

21. Hooking Fishes Individually

22. Fishing with nets

23. Stock Reduction - factors • Environmental change • “Random factors” • Overfishing

24. Vulnerable Fisheries • Life histories with long generation times • Life histories with low fecundity • Stocks with confined populations (aggregations or geographic range in a confined area) • Resource species that are easily caught • Top carnivores (less abundant)

25. Management Problems 1 • Fisheries managed by a variety of local and federal agencies

26. Management Problems 2 • Fisheries managed by a variety of local and federal agencies • Management recommendations not always in best interests of maintaining stock

27. Management Problems 3 • Fisheries managed by a variety of local and federal agencies • Management recommendations not always in best interests of maintaining stock • Some policies backfire - e.g., Magnuson Act of 1976 which extended US coastal fishing zone 200 miles from shore but resulted in extensive deployment of US fishng boats, resulting in overexploitation

28. Management Problems 4 • Fisheries managed by a variety of local and federal agencies • Management recommendations not always in best interests of maintaining stock • Some policies backfire - e.g., Magnuson Act of 1976 which extended US coastal fishing zone 200 miles from shore but resulted in extensive deployment of US fishng boats, resulting in overexploitation • Magnuson Act established 8 regional fishing commissions to help regulate domestic fishing - results good in some cases, bad in others

29. Effects of Overfishing 1 • Great reduction of many stocks, e.g., formerly productive Georges Bank, east of New England

30. Effects of Overfishing 2 • Great reduction of many stocks, e.g., formerly productive Georges Bank, east of New England • Effects concentrated especially on species with vulnerable life cycles (low fecundity, long generation time - e.g., sharks, whales)

31. Effects of Overfishing 3 • Great reduction of many stocks, e.g., formerly productive Georges Bank, east of New England • Effects concentrated especially on species with vulnerable life cycles (low fecundity, long generation time - e.g., sharks, whales) • Collateral effects on the bottom, where bottom trawling continually turns over the bottom, killing epibenthic animals

32. Effects of Overfishing 4 • Great reduction of many stocks, e.g., formerly productive Georges Bank, east of New England • Effects concentrated especially on species with vulnerable life cycles (low fecundity, long generation time - e.g., sharks, whales) • Collateral effects on the bottom, where bottom trawling continually turns over the bottom, killing epibenthic animals • Elimination of species at the tops of food chains, which tend to be lower in abundance and have vulnerable life history characteristics

33. Georges Bank Stock landings 3 Metric Tons x 10 Cod Atlantic Ocean Haddock Yellowtail Cape Cod Year GEORGES BANK Trends in landings of three major fisheries on Georges Bank on the New England continental shelf

34. Some new management tools • Individual transferable quota (ITQ) - licenses are limited in number with quotas for each license, which can be sold • Marine Protected Areas (also known as No-Take Areas) - some portion of the stock’s geographic range is closed to fishing - protects spawning grounds, nursery grounds, or minimal crucial habitat size to preserve stock even when fishing is too high

35. Spawning area Juvenile Feeding area No-take areas Adult feeding area Current and dispersal direction Adult feeding area Adult feeding area Hypothetical No-take Plan

36. Mariculture - Important Factors • Desirability as food • Uncomplicated reproduction • Hardiness • Disease resistance • High growth rate per unit area (growth efficiency) • Readily met food and habitat requirements • Monoculture or polyculture • Marketability • Minimal ecological damage

37. Mussels and Oysters • Mussels usually recruit to ropes and poles • Placement in areas of high phytoplankton density and water flow • Oyster newly settled larvae (spat) collected and then transferred to trays that are suspended from rafts • Problem: bivalve diseases, e.g., MSX in oysters - amoeboid protozoan

38. Harmful Algal Blooms (HABs) 1 • A variety of toxins, usually produced by species of phytoplankton

39. Harmful Algal Blooms (HABs) 2 • A variety of toxins, usually produced by species of phytoplankton • Toxins are consumed, along with phytoplankton cells, by resource bivalves, who sequester toxins

40. Harmful Algal Blooms (HABs) 3 • A variety of toxins, usually produced by species of phytoplankton • Toxins are consumed, along with phytoplankton cells, by resource bivalves, who sequester toxins • Toxins are then consumed by people

41. Harmful Algal Blooms (HABs) 4 • A variety of toxins, usually produced by species of phytoplankton • Toxins are consumed, along with phytoplankton cells, by resource bivalves, who sequester toxins • Toxins are then consumed by people • Seasonality allows regulation in some cases (e.g., prohibition of exploitation of coastal mollusks in California from May-August)

42. Major HAB types 1 • Paralytic Shellfish Poisoning (PSP) - variety of neurotoxins produced by dinoflagellate species of Alexandrium, Gymnodiniums, Pyrodinium - strong neurotoxic effects, respiratory arrest, occasional death • Amnesic Shellfish Poisoning (ASP) - domoic acid produced by species of the diatom Pseudonitszchia - causes amnesia, neurological damage, even death

43. Major HAB types 2 • Neurotoxic Shelfish Poisoning - caused by brevitoxin, produced by dinoflagellate Gymnodinium breve, can be breathed from aerosols • Pfiesteria piscicida - toxin not identified, but causes severe neurotoxic effects, one of many life history stages of this species emerges from the bottom and can attack fish.

44. Spread of HABs 1 • Frequency and geographic extent of HABs are increasing • Harmful species often affect shellfish physiology as well as humans and may kill entire populations (e.g., killing of bay scallop Argopecten irradians by “brown tide” organism in waters of New York)

45. Spread of HABs 2 • Increase may be a result of increasing disturbance and pollution of coastal zone, or more frequent introductions from shipping traffic • Increase results in more frequent closures of shellfish beds, fish kills (Pfiesteria), sickness,

46. Seaweed Mariculture • Nori - derived from red Porphyra spp., rich in protein, used to wrap sushi, spores collected on nets and grown in estuarine areas • Kelps - grown actively in western U.S. coastal waters, harvested for alginates, used in a number of foods • Many others, some harvested directly from shore

47. Fish Ranching • Marine fish, such as salmon species, are grown in open water tanks • Genetic engineering now being used to introduce fast-growth forms • Problem - many escape and mix with wild salmon (1/3 of salmon in Norwegian rivers derive from ranched salmon) • Problem - feeding carnivores requires a lot of food (overfishing other stocks?)

48. The End