1. 18 Fisheries and Food from the Sea
Notes for Marine Biology: Function, Biodiversity, Ecology
By Jeffrey S. Levinton

2. Fisheries
Relatively primitive form of food acquisition - hunting and gathering
Fishery is potentially 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 - a fishery species is divided into stocks, which are populations that are geographically definable and consisting of individuals responding to similar environmental factors
Stock - is also a fisheries management unit (nursery, feeding area, political boundaries, fishing limits)

4. Identification of Stocks
Tags - utility depends on rate of recovery, time period that they last, define movement
Biochemical and molecular markers - identify different stocks (analysis important) that have become genetically isolated and distinct
Stock identification important in societal disputes about fishing policy

5. A striped bass, Morone saxatilis, tagged ventrally with an internal tag

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

7. Life History and Stock Size
The life history of a fishery species and the size of the
stock must be understood before sensible planning can
be done regarding fishery management
Stock size could be surveyed by scientific surveys, BUT
The size of a stock is mainly assessed by quantity of
landings by fishers, which is principally a function of the
population size, the spatial variability of the fish, and
the amount of fishing effort
Fishing effort is the amount of effort per fish caught, including number of boats and fishers, hours per fisher per unit time, type of gear; fishng effort can also be estimated by fuel consumed

8. Landings by year of the blue whale, as compared with effort
Catch per catcher-day’s work
Year

9. Crucial Life History Information Needed
Physiological limiting factors
Spawning/nursery habitat
Feeding areas
Migration routes
Biological information that minimizes unintended mortality during fishing

10. To produce a good fisheries model, we must account for all contributions to reproduction, growth, and mortality throughout the life cycle of the fishery resource species

11. 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

12. Age, Origin - Crucial Data
Age: size distributions, growth bands (otoliths)
Origin - tags, transmittors, trace element chemistry of otoliths (Thorrold et al Can J. Fish Aquatic Sci.) 57: [laser ablation - mass spectrometry - Mn, Sr, Ca variation in various locations]

13. A cross section of an otolith of the bluehead wrasse Thalassoma bifasciatium that settled from the plankton at a length of 13 mm; growth record reveals the 41-day mark after hatching, when settlement on the bottom occurred (transition between closely spaced lines and relatively broad band); otolith is about 300 μm long

14. Identification of age classes by size: lobster Panuliris ornatus

15. Model of Fishery Population
The health of a stock can be assayed by its production,
which is explained in terms of growth of previous year
classes and recruitment into the new year class
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

16. 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

17. Stock-recruitment model
120 40 80
Recruitment
Density-dependent
effects
Stock in previous year
Stock-recruitment model

18. Logistic model: model that can describe declining recruitment at increasing population density

19. Maximum Sustainable Yield Model
Based on idea that a fishery stock will grow at a slower rate over a certain stock size
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 and Evolutionary Response
Fishing can exert evolutionary changes in life history on fished populations
If there is genetic variation for growth rate, size specific fishing can change genetic variation in population
Harvest larger-sized individuals, get dominance of smaller individuals
Might lead to lower fish production, because of dominance of genotypes causing smaller size/growth rate
See Conover and Munch 2002, Science

21. 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

22. Hooking Fishes Individually

23. Bycatch
Unintended catch, may be discarded overboard, set aside for other purposes, such as fish meal
Constitutes much of world catch
Example: sea turtles, trapped in shrimp nets, may drown while netted and brought aboard
Solution: turtle-exclusion device (TED), encourages turtles to swim away through escape hatch before being trapped

24. Stock Reduction - Factors
Environmental change
“Random factors”
Overfishing

25. Vulnerable Resource Species
Long generation times (e.g., whales)
Low fecundity (e.g., many shark species)
Geographically confined populations (aggregations or geographic range in a confined area)
Easily caught
Top or apex carnivores (less abundant)

26. Relative declines among shark species are shown by setting starting abundance at 1; coastal shark species: (a) hammerhead, (b) white, (c) tiger, and (d) coastal shark species identified from 1992 onward; oceanic shark species: (e) thresher, (f) blue, (g) mako, and (h) oceanic whitetip

27. Causes of Stock Reduction
Stock reduction can result from random variation as well as from environmental change; fishing would be superposed on the effects of these factors and appears to cause greater fluctuations than when fishing is absent
Fish stocks characterized by long generation times, small clutches of eggs, and fewer spawnings over time are the most vulnerable to overfishing
Fishing has initiated or accelerated the decline of many stocks

28. Management Problems
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 U.S. coastal fishing zone 200 miles from shore but resulted in extensive deployment of U.S. 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
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)
Bycatch
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

30. Trends in landings of three major fisheries on 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, late 1970s to 1990s

31. Overfishing and Trophic Cascades
Remove top predator from fishing - get reorganization at lower trophic levels
Likely in nearshore fisheries with confined populations
Gulf of Maine Cod removal1990s --> increase in shrimp, snow crab (Frank et al. 2005, Science)
Other cases, North Sea, open Pacific, no evidence for reorganizations

32. Cures for Overfishing
Better models: more effective fishing approaches use models that show the impact of mortality on different life-history stages.
Closures and Limits: temporary closures and fishing limits allow some fisheries to be sustainable
Quotas: quotas might produce a sustainable fishery.

33. Some New Management Tools
Individual transferable quota (ITQ) - licenses are limited in number with quotas for each license, which can be sold involves a Total Allowable Catch (TAC) - e.g., rock lobsters, Australia (
Marine Protected Areas (also may be known as No-Take Areas, Marine Reserves) - 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
Ecosystem-Based Management - consideration of entire ecosystem including human societal needs

34. Design of no-take areas in a hypothetical fishery; the spawning and juvenile feeding areas and one adult feeding ground are no-take zones, to allow a minimum population to complete a life cycle. other areas might be fished, although quotas might be set on the amount of the take.

35. Fisheries recap Necessary knowledge - life history
Estimate of fishery size - stock (prop. to N, fishing effort-landings)
Fisheries models - e.g., Stock Recruitment Model
Over fishing - management problems (e.g., jurisdiction, Magnuson Act, political pressure by fishing groups)
Vulnerable fisheries - life cycle, top predators
Fishing down the food chain, trophic cascades

36. Whaling and Overfishing
Life cycle of cetacea - extended generation time, small number of young, long gestation
Expansion of range of boats -shore to open ocean
Change in technology
Three periods:
12th century s - shore based small boats
1820s Land based and ships
present - pelagic (e.g., Antarctic) whaling

37. Shore-Based Fishing Long Island - Baymen - coastal fishing
Bay of Biscaye - Biscayan Right Whale eliminated in 1600; by 1700s too few to exploit in N. Atlantic (by 1800s, ships hunted them to near extinction)
California grey whale - hunting began 1851 in nursery grounds, whaling ceased in 1890, 100 left by 1936…today expansion to <10,000

38. Ship-Based Whaling
1820s Nantucket station - Atlantic sperm whales hunted to near extinction
1820s -1850s switched to Pacific (Moby Dick, Essex)
1860s - cannon-powered harpoon, use of catcher boats and factory processing ship
Iceland is a base for whaling
1890s - Antarctic stocks discovered
1920s - stern slipway used, factory ships
1920s - WWII decimation

39. Whaling management
1930s - Various agreements signed (without Japan and Germany), Blue Whale Unit
IWC instituted - objection power
management of catch, season, size
1971 Observers, BWU dropped in Antarctic
1980s whaling almost ceased in Antarctic (scientific whaling); 1982 moratorium, Japan accepted it in 1987
Currently pressure to resume whaling (Norway objection), Japan “scientific whaling”
Blue Whale Unit (BWU) = 2 fin whales = 2.5 humpbacks = 6 sei whales

40. Indian Ocean Whale Sanctuary
Southern Ocean Whale Sanctuary

41. Blue Whale
Fin Whale
Sei Whale
Minke Whale
Antarctic Whale Stocks

42. Recovery? Minke whale - pressure to refish
Humpback, Blue whale in eastern Pacific, increasing
Antarctic Blue whale, Northern Right Whale, no increase
Japan scientific whaling - not just Minke whale (Baker and Palumbi 1994)

43. 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

44. 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

45. Harmful Algal Blooms (HABs)
A variety of toxins, usually produced by species of phytoplankton
Toxins are consumed, along with phytoplankton cells, by resource bivalves, that 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)

46. 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

47. Major HAB types 2
Neurotoxic Shellfish Poisoning - caused by brevitoxin, produced by dinoflagellate Gymnodinium breve, can be breathed from aerosols
Pfiesteria piscicida - toxin causes severe neurotoxic effects, one of many life history stages of this species emerges from the bottom and can attack fish

48. 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)

49. 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

50. 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

51. 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?)

52. The End