Marine p2 Flashcards
World fishery situation
• Total fisheries production not increasing
– But Aquaculture increasing fast (high demand, prices)
• Many fisheries over‐exploited
– Sharks especially vulnerable, due to reproductive traits
Plus shark finning is rife (international illegal trade).
• We need sustainable fisheries
– Politicians will not enforce sustainable management without strong consumer pressure (Remember why).
– Countries that maintain fisheries will gain in future.
Australian fisheries
- Australia’s fish fauna is diverse
- Australia controls a very large fishing area
- But fishing is mostly in temperate waters
- And the total catch is small relative to other countries
- However, we catch many very valuable species
- In general, we manage these very well, to sustain them
Australia Aquaculture
• Aquaculture produces valuable species
• Key valuable export species are Southern bluefin tuna, Salmon,
rock lobster, abalone, prawns, and pearl oysters
Aquaculture and Disease
• Farms crowd animals into tanks/nets to make good profits.
• But this means it is easy for diseases to spread between the
fish/abalone/prawns etc.
• Often farm animals are stressed – so more vulnerable to infection.
• Diseases can be incredibly costly to a farm!
• So disease prevention is a key research issue for aquaculture
Also, aquaculture worldwide has often spread disease into fisheries
Southern Bluefin Tuna
• One of the most expensive fish (up to $18000/fish)
• Wild fishery over‐exploited, now endangered
– Most Fishing at the edge of current eddies in Aust. Waters
– Problem is enforcement when fished by several countries
• Spawns off Australia’s northwest coast
– Larvae drift and grow in the Leewin current
– Reach the south coast as juveniles
• Caught in seine nets, put into sea cages in WA, SA
– Fed with frozen pilchards until large
– Snap frozen for sale in Tokyo market at top prices
– But 2‐12 kg of fish food to get 1Kg of SBT!
Shark and abalone fishery e.g.s
- Each fishery may need different management.
- Sharks managed by enforcing gillnets with an optimal mesh size and requiring fishers to avoid vulnerable bycatch species.
- Abalone managed by engaging divers to assess local size limits and optimise sustainable catches (co‐management by industry and government)
- Political lobbying causes most problems in enforcement of management.
Diversity and
Distribution of Freshwater fish
• We have relatively few freshwater species compared to other continents
– This is a result of few permanent rivers, as Australia has no high mountain ranges and so is very dry.
• But we have some very unique species of fish and crustaceans (e.g. Lungfish, Barramundi, large FW crayfish).
Cause of diversity in fresh water fish
• River captures (due to erosion of the dividing range), river course changes and sea‐level changes transfer species between rivers
– After that the species gradually evolve into new species
– Several examples with Murray cod
Our Effects on
Australia’s Fresh water fish.
- Fishing pressure reduced Murray cod numbers.
- Dams have disrupted diadromous migrating fish.
- This includes the unique Queensland lungfish.
- More dams on northern rivers will affect Barramundi + other species
- Introduced alien fish (esp. trout) devastated many small native fish.
- Recreational fishers often make this worse.
- Over‐allocation of water to irrigators has led to low flows, and thus Blue‐green algal blooms that kill fish by using the oxygen.
- Climate change is reducing rain in the south, so this will get worse!
- Climate change warming also reduces the DO in the water.
algae
There are many groups of algae and they are spread around the eukaryotic tree of life.
The overall cell structure, particularly the plastid, unites algal cells
Diatoms
Diatoms are a major group of microalgae made up of 50% of ocean biomass.
They have a glass (SiO2) cell wall.
They have golden-brown pigmentation.
Coccolithophores
Coccolithophores (haptophytes) have a calcareous (CaCO3) cell wall.
They have golden-brown pigmentation
Dinoflagellates
Dinoflagellates have a cellulose cell wall.
They have golden-brown pigmentation.
They have interesting locomotion using two flagella.
Many are predatory
Green algae
Green algae have a cellulose cell wall.
They are common in near-shore environments.
They have green pigmentation.
Picoplanktonic forms are extremely small.
Cyanobacteria
Cyanobacteria are prokaryotes with a peptidoglycan cell wall.
Perhaps the most numerous photosynthetic organisms.
They have all sorts of pigments.
