Fisheries and conservation

Question 1

Human Fish interactions

Answer 1

Since 150,000 to 100,000 years ago from south africa and europe.
Fishing is a part of cultural identity, particularly in island and coastal communities
1884 Huxley said fisheries are inexhaustible and anything we do is useless.

Question 2

Whaling

Answer 2

For whale oil was a major fishery in the North Atlantic in the second half of the 19th century.
By late 1880s populations of baleen whales had declined so much that a profitable fishery was impossible.

Question 3

Fisheries

Answer 3

Aims to safeguard both fish populations and fisheries.
Fisheries in 19th and 20th century follow pattern with the tragedy of the commons.
Shifting baselines:
- in a declining environment and compare it to what we used to see, for restoration what should we compare it to.
Stakeholders:
- Who benefits from fish resources and who - should they be managed for.
- Commercial fishers for economic benefit
- Recreational fishers
-Whales or sharks that prey on commercial fish, and tourists who want to see them

Question 4

Fisheries science

Answer 4

population biology and economics, increasingly uses ecology to consider fishereis as complex social and environmental features
Fishery: Combination of the biological fish population and the human fisheres. Fishers may be defined according to a species or a region

Question 5

Aim of fisheries management

Answer 5

Ensure that catch rates do not exceed potential rates of replenishment.
Maintain the capability of the ecosystem to sustain the stock.
Ensure catches and profits are sustainable in the long term.
State of world fisheris is evaluated and summarised every 2 years by UN State of World Fisheries and Aquaculture (SOFIA) reports.

Question 6

Maximum sustainable yield (MSY)

Answer 6

In a population without limits, growth is exponential and rate of change of population size is constant.
Rate of change is determined by differentiating the curve is termed r.
If the environment imposes a limit on population growth, then the rate of population will slow as the population size approaches the carrying capacity (K).
When population size = K, the rate of population growth must be 0.
Can then consider population growth rate as a function of population size.

Question 7

Population size with growth rate

Answer 7

1. small population
   Size is far below capacity, rate of growth is limited by number of individuals, so rate of growth will increase as number of individuals increases.
   If population is here you should not fish.
2. MSY
   Where rate of population growth is maximised Aim of MSY fishing is to fish populations to maintain size at MSY.
   Maximises return to fishery and doesn’t collapse population
   Population sizes for single stocks at MSY are approximately half of the unfished stock size.
3. large population
   Here the population size is trending towards the capacity.
   Population growth rate limited by competition.
   Fishing at this part reduces competition and increases growth rate, SUSTAINABLE.
   Stock is surplus production

Question 8

MSY limitations

Answer 8

Fishing to maintain a population size at MSY good for fish and fisheries.
However is risky.
Impossible to fish many species to MSY in same ecosystem as populations are interlinked through predator-prey relationships.
Management to MSY is expensive and may be impossible to sustain in many economies

Question 9

Modern management

Answer 9

Tools of management are policy and regulation, manager fishers not the fish.
Mostly implemented by restrictions on fishing effort.
Or through quotas, establishment of closed seasons or MPAs.
Net effect is to limit amount of fishing when a population appears to be in trouble.

Question 10

Hilborne paper

Answer 10

Looked at ratio between the biomass in any year compared to the biomass at MSY, values above 1 indicate good fishery status.
Ratio between fishing compared to fishing at MSY, values below 1 suggest need for regulation
Data showed before 1990 biomass was falling to MSY, but effort was above maximum, led to fisheries collapse.
Gov action and restricted fishing and biomass increased.
Regulation works and depleted stocks will recover.

Question 11

Stock

Answer 11

Stock: Part of the population of a commercially exploited species that is reproductively isolated and managed as a single unit.

Question 12

Yield

Answer 12

Yield: Numbers of fish produced by recruits and available to a fisher

Question 13

Recruit

Answer 13

Recruit: Fish that survives from an egg until reproductive or legal fishery age.