Who, What, When, Where, Why, and How of The Ocean’s Resources

1. Who, What, When, Where, Why, and How of The Ocean’s Resources • Who harvests the ocean’s resources? • What does “harvesting the ocean’s resources” mean? • When does harvesting become overharvesting? • Where does overharvesting occur? • Why is harvesting from the ocean necessary? • How do humans harvest from the ocean?

2. Chapter 19 Harvesting the Ocean’s Resources

3. Key Concepts • Fish and shellfish are renewable resources that must be properly managed to produce a sustainable yield. • Increased demand for food from the sea has placed a great deal of pressure on natural fish and shellfish populations.

4. Key Concepts • The advent of mechanized fleets and better fishing techniques, coupled with natural phenomena, has caused a decrease in the size of commercial fish catches. • Overfishing has brought some fisheries to the brink of collapse. • Techniques such as aquaculture have helped relieve fishing pressure on natural populations but not without new impacts on natural environments.

5. Key Concepts • Large numbers of noncommercial animals are killed as a result of current, mechanized fishing techniques. • Our limited knowledge of the basic biology of many commercial species hampers our ability to properly manage and conserve these resources.

6. Key Concepts • The sea is an important source of minerals, including salt (NaCl) and manganese, and the sulfides of valuable metals such as gold and uranium. • Fresh water for drinking and irrigation can be produced from seawater by removing the salt. • The oceans contain energy reserves in the form of fossil fuels and methane hydrate.

7. Commercial Fishing • Commercial fisheries are in trouble • article published in the journal Science in 2006 projected that by 2048, commercial fishers will have nothing left to catch • There has been a dramatic increase in fish/shellfish taken from the sea in the past 50 years • increased demand resulted from increase in the human population (now more than 6 billion)

8. Commercial Fishing • Use of the catch has become less efficient as more is used for fish-meal products to feed livestock • 10% rule of ecology • only about 10% of energy available at one trophic level is passed on to the next • feeding livestock with commercial fish not efficient • commercial fish catch consists of fish in higher trophic levels (e.g., tuna) • greater waste of energy than harvesting fish on lower trophic levels

10. Commercial Fishing • Fisheries management • fish and shellfish are renewable resources as long as animals who aren’t caught continue to reproduce and replace those that are caught • the goal of fisheries management is to maintain these resources by enacting policies and setting catch limits that will prevent overfishing • this is difficult when the basic biology of a commercial species is not well known

11. Commercial Fishing • Fisheries management (continued) • monitoring fish populations • determining population distribution and movement • some commercial species can be found over a broad geographical range • range is divided into stocks (separate populations) for purposes of management • tagging: catching fishes and marking them with identification tags, used when they are re-caught • by mapping locations where tagged fish are initially caught and released and released again, biologists track movement and distribution of members of each stock • unique molecular markers (DNA sequences) can be used to identify members of specific stocks

13. Commercial Fishing • Fisheries management (continued) • monitoring fish populations (continued) • determining population size and age structure in order to develop sound management plan • sampling experiments are designed to determine the number of individuals of various ages and sizes in a given stock • landings: the catch made by fishing vessels, monitored as a source of fisheries data • fishing effort: the number of boats fishing, number of fishers working, and number of hours they spend fishing

14. Commercial Fishing • monitoring fish populations (continued) • fishery yield • potential yield: the number of pounds of fish or shellfish that the stock can yield per year without being overexploited • sustainable yield: the maximum yield that may be sustained over several years without stressing the population • problems in managing diverse species • proper management of one species may conflict with proper management of other species • some fisheries biologists prefer to take an area or ecosystem based approach

15. Commercial Fishing • Overfishing • occurs when fish are caught faster than they reproduce and replace themselves • changes in genetic diversity by selecting for or against a certain trait • harvesting larger specimens leaves only smaller ones to reproduce, exerting a selective pressure for smaller animals • trawls: large nets that are dragged along the bottom, capturing virtually everything that enters • overfishing reduces population size, hence reducing genetic diversity

17. Commercial Fishing • Overfishing (continued) • changes in species diversity • overfishing can affect biological diversity by reducing the number of species in an ecosystem • changes in habitat • fishing activities, e.g., trawling, can damage or destroy habitat ultimately disrupting entire ecosystems

18. Commercial Fishing • Overfishing (continued) • controlling overfishing • coastal zones • In 1977, the United States and other countries increased the area of ocean controlled by them to 200 miles off the coast = exclusive economic zones (EEZs) • developing new fisheries (e.g., surimi) as a consequence of decreasing traditional fisheries (e.g., tuna) • consumer education • hoping to curb demand for endangered species

20. Commercial Fishing • Other factors affecting marine fisheries • destruction and development of coastal habitats • resulted in a loss of feeding, breeding and nursery grounds for commercial fishes • wasteful and destructive fishing practices • incidental catch: non-commercial species killed each year during commercial fishing (a.k.a. bycatch or “trash fish”), representing significant waste of marine resources • drift nets: large nets made of sections called tans which are set at night and retrieved in the morning • Produce large amounts of bycatch

22. Commercial Fishing • Other factors (continued) • wasteful and destructive fishing practices • trawling produces a large bycatch and damages benthic ecosystems • shrimp trawlers catch and kill many sea turtles • use of turtle exclusion devices reduces turtle deaths • inefficient use of the catch • e.g., filleting process uses only 20 to 50% of fish’s body weight

23. Commercial Fishing • Other factors (continued) • aquaculture: the use of agricultural techniques to breed and raise marine organisms • monoculture: only 1 species is raised • polyculture: several species are raised together • fish aquaculture • raft culture: juveniles of commercially valuable molluscs (clams, mussels, oysters) are collected and attached to ropes suspended from rafts

26. Commercial Fishing • Other factors (continued) • aquaculture (continued) • shrimp farming • eco-friendly aquaculture • problems associated with aquaculture • mangrove ecosystems are destroyed in Ecuador and Asia to make room for shrimp farms which quickly become polluted from accumulated wastes and abandoned • large numbers of fish must be caught to supply food for shrimp and salmon aquaculture, making these fish unavailable to support many fish species in the wild • antibiotics and pesticides along with nutrients used in aquaculture become harmful runoff into coastal waters

27. Commercial Fishing • Case studies • tuna • purse seines: huge nets up to 1,100 m long and 180 m deep with bottoms that can be closed by pulling on a line • purse seines exploit schooling behavior of tuna • dolphins follow tuna in and get caught and killed • Marine Protection Act passed in 1972 • backing down: procedure in which the skiff draws the purse seine halfway toward the purse seiner; when the dolphins are at the edge, the boat backs up to let them escape

29. Commercial Fishing • Case studies (continued) • salmon • to maintain salmon fisheries, overfishing must be avoided and their spawning grounds protected • disruption of spawning grounds has made the spawning population quite small • ocean ranching (sea ranching): raising young fish and returning them to sea, where they develop into adults and increase the size of the population

32. Commercial Fishing • Case studies (continued) • Shellfish • invertebrates (crustaceans and molluscs) are the most valuable commercial fisheries in New England and along the West Coast of the United States. • hard-hit by pollution that contaminates estuaries and near-shore waters • toxic algal blooms render some shellfish poisonous • the king crab fishery declined in the 1980s and is now regulated • overfishing + lack of knowledge about king crab biology have been blamed for this decline

34. Salt and Water • Obvious non-fisheries products of the sea • 30% of the salt supply comes from the sea; 70% from deposits left when ancient seas evaporated • Extraction of salt from seawater • seawater is directed into shallow ponds where it is concentrated, then evaporated

35. Salt and Water • Desalination—process of removing salts from seawater (so it is potable) • process is energetically/financially expensive • usually more expensive than obtaining water from groundwater or surface sources • used in Israel, Saudi Arabia, Morocco, Malta, Kuwait, Caribbean islands, parts of Texas and California

36. Mineral Resources • Sulfides • formed when mineral-rich solutions from fractures in rift valleys come into contact with colder seawater, and precipitate • no technology exists for sampling/mining at this time • Manganese • used as a component of several alloys • nodules are found on the deep ocean floor • attempts to develop mining technology were largely suspended in the 1980s due to the depressed market for metals and issues of ownership

37. Sand and Gravel • Most widespread seafloor mining operations extract sand and gravel for use in cement, concrete and artificial beaches • major costs associated with transportation distances • Calcium carbonate deposits along Texas Louisiana and Florida • used for lime, cement, calcium oxide for removing magnesium from seawater, gravel • Tin is extracted from sand in coastal regions of Southeast Asia

38. Sand and Gravel • Uranium extracted from bottom sediments of the Black Sea • Platinum extracted from coastal sands in the U.S., Australia, South Africa • Mining sands/gravel can cause pollution and habitat destruction in the marine environment

39. Energy Sources: Coal, Oil, Natural Gas, and Methane Hydrate • Fossil fuel is fuel (coal, oil and natural gas) formed from remains of plants and microorganisms that lived millions of years ago • Coal • formed from prehistoric swamp plants, e.g., ferns • coal is mined from under the sea in Japan • Oil and natural gas • represent 90% of the mineral value taken from the sea • formed from remains of diatoms and other microorganisms • oil is mined in the Persian Gulf, North Sea, Gulf of Mexico, northern coast of Australia, southern coast of California, and around the Arctic ocean • offshore reserves represent about one third of world’s total reserves • cost of offshore drilling and extracting is 3 to 4 times that of land-based operations