Fisheries and Aquaculture

Question 1

What makes an organism susceptible to overfishing?

Answer 1

Sessile of sedentary
Aggregative behaviour
Limited home ranges
Specific habitat requirements
Serial Depletion
Source-sink Dynamics
Lack of data - lack of regulation and management

Question 2

Management of Molluscan Fisheries - Example Pink Abalone. What are the characteristics, fishing method and challenges associated with Pink Abalone?

Answer 2

• Characteristics: sedentary, small, slow growing, aggregate, difficult to
  age, cryptic juveniles.
• Fishing Method: Hand gathering (easily harvestable)
• Challenges: Spatially discrete, data deficiencies, variable recruitment

Question 3

Management of Echinoderm Fisheries -
Example Kina. What are the characteristics, fishing method and challenges associated with Kina?

Answer 3

• Characteristics: Slow growth, seasonal reproductive cycle, variable recruitment
• Fishing Method: Breath hold diving, some historic dredging
• Challenges: variable growth and mortality, recruitment overfishing, trophic interactions

Question 4

Management of Arthropod Fisheries –
Example American lobster. What are the characteristics, fishing method and challenges associated with the American Lobster?

Answer 4

• Characteristics: Long lived, bottom dwelling,
  solitary and territorial, difficult to age, small
  home range, seasonal migrations
• Fishing Method: Pots, traps, gillnets, trawls, diving
• Challenges: Climate change, disease, jurisdiction

Question 5

For this list of 5 invertebrate groups give 2 factors that make fisheries management challenging for each group.
- Sea urchins
- Crustaceans
- Sponges
- Molluscs
- Corals

Answer 5

• Sea urchins - variable growth and mortality, recruitment overfishing
• Crustaceans - disease, issues with jurisdiction
• Sponges - issues with regulation, issues with algal blooms
• Molluscs - spatially discrete, data deficiencies
• Corals - slow recovery, issues with climate change

Question 6

What 10 things make a species good particularly suitable for aquaculture>

Answer 6

1. Ease of breeding (spawning)
2. Early maturity
3. Fecundity
4. Ease of rearing larvae/spat
5. Growth
6. Dietary Requirements - low and cheap
7. Economic value - increasing
8. Increasing water quality
9. Low space requirements
10. Create sustainable habitat

Question 7

Explain the 7 things that make a species good to grow in captivity with an example (Mussels).

Answer 7

Case Study - Green Lip Mussels
1. Gonad stripping, induced spacing, thermal shock, thermal cycling, gonad injection.
2. From about 1 year of age mussels are sexually mature - they can produce and store eggs and sperm in preparation for spawning
3. High fecundity
4. Mussel spat develop from a floating larval stage (pediveliger), larvae attach themselves to seaweed or ropes and develop, they move site to site until they are 0.6mm in length and then they attach themselves to a settlement site.
5. Once settled, they grow rapidly, Harvested when they reach about 10cm.
6. Mussels trap phytoplankton which are easy to feed.
7. Enough economic value to pursue growing in captivity.

Question 8

What are the potential negative effects of aquaculture/fisheries?

Answer 8

• The degradation of host environment
• Disruption of the host community
• Genetic degradation of the host stock
• The introduction of diseases and parasites

Question 9

Discuss the advantages of aquaculture using examples where appropriate.

Answer 9

• There are benefits to water quality using and marine habitats (usually with filter feeders)
• There is no terrestrial equivalent to aquatic filter feeding - you do not need to add extra feed to feed them
• Aquatic organisms occupy volume not surface area so there is a high reproductive rate
• Marine organisms have absence of thermal regulation and higher conversion efficiencies - so energy on maintaining bodily processes is less than terrestrial stock