Demersal Fisheries Flashcards
Demersal Fisheries
Targeted fisheries that are along the bottom of the water column.
Also called groundfish fishery
Characteristics of a Demersal Active Fisheries
-Trawling gear used
- Can get a lot of species within this – rarely is there a single target – more difficult to focus in a single species.
- Occur in waters over the continental shelf (200m) but can move offshore
Potential limitations for the demersal fishery:
Often 20 or more species are vulnerable to the fishing gear (even more stocks!)
Underestimated when it comes to stock
Can assess the stocks/species individually
Cannot manage the stocks/species individually
Mainly two families that make up the demersal fishery. What are the two families?
- Godiformes
-Pleuronectiformes
What are the main species within the Godiformes family?
Cod, Haddock, hakes, and grenadiers
Characteristics of the Gadiformes family
- Primarily marine
- World-wide
What are the main species within the Pleuronectiformes?
- Yellowtail flounder
- Witch flounder
- American plaice
- Winter flounder
- Windowpane flounder
- Atlantic halibut
Monophyly
A group composed of a collection of organisms, including the most recent common ancestor of all those organisms and all the descendants of that most recent common ancestor
Characteristics of a Pleuronectiformes
- Monophyly (mostly not questioned)
- Cranial asymmetry due to ocular migration
Types of ocular migration:
Right-eyed (dextral), lie on left side
Left-eyed (sinistral), lie on right side
Both (Psettodes)
What other species make up the rest of the demersal fishery?
- Acadian Redfish
- Ocean Pout
Atlantic Cod - Biological Characteristics
- Found throughout the North Atlantic
- Fast growing (Max size 2m)
- max-age ~ 25 yrs
- Winter Spawners
- High fecundity (batch spawners)
- Live first few months at surface before going to bottom.
Batch Spawn
Females capable of ovulating and spawning multiple batches of oocytes during the individual spawning period. Batch spawners can have determinate or indeterminate fecundity.
Shrinking Fish Syndrome
When Atlantic Cod are fully mature, they are about two meters long. Since they are recruiting between ages 1 and age 2, they are not allowing the fish to reach their full-size potential. This has resulted in significant declines in size and age at maturity.
1930s- 85 cm
1970’s - 82cm
2000’s - 73cm
Atlantic Cod Fishery
- Extremely old fishery dating back to Roman times.
- There was a perception there was a limitless catch.
- Many wars have been fought over territorial waters for Cod fishing.
- Crash of the fishery in the 1970’s.
