Pelagic Fisheries

Question 1

Pelagic Fisheries

Answer 1

Fish within the water column – not associated with the bottom

Water column can be shallow or very deep

Question 2

What are the water column layers based on the types of fisheries?

Answer 2

1. Zooplankton
2. Forage Fishes
3. Large Pelagics
4. Demersals
5. Benthic Invertebrates

Question 3

Do fish mainly stay within their water column zone?

Answer 3

No, there is spatial relationships between different species within multiple water columns.
- Life history stage dynamic as well.

Question 4

What distinguishes between large forage fish and large pelagic fish?

Answer 4

Movement

Question 5

Biological Characteristics of Large Pelagic

Answer 5

Most are top level predators

Feed on smaller fish and squid

High metabolic rates

Several species maintain elevated temperatures in some body regions

Highly migratory

Question 6

Life History Biological Characteristics of Large Pelagic

Answer 6

High fecundity

Broadcast spawning over a large geographic area (except bluefin tuna)

Rapid growth

Most species reach sexual maturity at 2 – 4 years (except bluefin tuna)

Can be relatively long-lived (6 – 20+ years)

Question 7

What species of pelagic fish is excluded from the life history?

Answer 7

Pelagic sharks

Question 8

Fecundity

Answer 8

the ability to produce an abundance of offspring or new growth

Question 9

Surface Fisheries Gear used for Pelagic

Answer 9

Purse seine (w/ & w/o FADs)
Baitboat (w/ & w/o FADs)
Trolling
Drift gill net
Recreational fishery

Question 10

FAD

Answer 10

Fish aggerated devices

Question 11

Subsurface fisheries gear types

Answer 11

Pelagic longline

Question 12

What are the major species within the pelagic fishery

Answer 12

• Tuna
• Wahoo
  -Swordfish
• Billfishes
  -Dolphin/Mahi Mahi

Question 13

What are the two pelagic shark species that are considered within this fishery?

Answer 13

• Shortfin mako
  -Blue shark

Question 14

What is the commonality between all of the species within the Scombriformes?

Answer 14

Not exclusive but most are highly migratory

Question 15

What is one of the most valuable fish on the market?

Answer 15

Bluefin Tuna (some sell for millions of dollars)

Question 16

What is the main family of the pelagic fishery?

Answer 16

Scombriformes

Question 17

What are the seven families of the Scombriformes?

Answer 17

Scombrolabracidae – escolar
Sphyraenidae - barracudas
Gempylidae - snake mackerels
Trichiuridae - cutlassfishes
Scombridae – tunas
Xiphiidae - swordfishes
Istiophoridae - billfishes

Question 18

Characteristics of the Scombridae family

Answer 18

“Two” dorsal fins, depressible into grooves
Finlets present
Scales small, cycloid
Some are endothermic (produce their own body heat)

Question 19

What are the characteristics of the Istophoridae & Xiphiidae

Answer 19

Elongate premaxillary bill (rostrum)
Finlets absent
Dorsal fin far anterior
Extremely well-developed zygapophyses

Question 20

zygapophyses

Answer 20

one of the two paired processes of a vertebra that interlock it with the adjacent vertebrae.

Question 21

What is the commonality between Scombridae and Istiophoridae/Xiphiidae?

Answer 21

Fast swimming - Can tuck all of the fins in to eliminate any drag.

Question 22

What Scombridae species has the broadest thermal tolerance?

Answer 22

Atlantic Bluefin Tuna

Question 23

Atlantic Bluefin Tune Biology

Answer 23

• Max size/ age - 679 kg; 300+ cm FL; 35+ years
• Oceanodromous
• Significant time at surface but capable of diving to 800 m
• Juveniles - shallower and closer to shore in summer

Question 24

An interesting fact about Atlantic Bluefin Tuna

Answer 24

There are two stocks within the Atlantic—one with a Gulf of Mexico Spawning Ground and the eastern stock with a Mediterranean spawning ground. These stocks differ in maturity schedules.
- W - 50% at age 4
- E - 50% at age 5-12

Question 25

Atlantic Bluefin Tuna : Eastern Stock/Fishery

Answer 25

• Centuries of fishing with traps in the Mediterranean
• Norway & Germany developed a purse seine fishery in the 1950s and 60s
• Led to major overfishing

Question 26

Why was the purse seine technique so detrimental to the fish stock for Bigeye Tuna?

Answer 26

They are a mixed school species. Similar size species school together. LL is more selective. Purse Seine will get all species within the net. It is catching the immature individuals.

Question 27

Bigeye Tuna Biology

Answer 27

• max size/age - 200 kg; 300+ cm FL; 16 years
• Oceanodromous, but the relatively little long-distance movement
• Atlantic is genetically distinct

Question 28

Changes in the Bigeye Tuna Fishery

Answer 28

Catches of juvenile bigeye increase as skipjack fishery increases (juvenile bigeye co-school) with skipjack

Increased purse seine fishing on FADs which tend to have the smallest bigeye

Leads to growth overfishing of bigeye tuna

Change in the selectivity of the fishery results in lower MSYs

Question 29

Maximum Sustainable Yield

Answer 29

The highest possible annual catch that can be sustained over time, by keeping the stock at the level producing maximum growth

Question 30

Growth Overfishing

Answer 30

is when fish are harvested before they reach the size where yield per recruit is optimized; the weight and value of the catch may be reduced

Question 31

Swordfish Biology

Answer 31

• Max age is difficult to determine (Otoliths are often too small to determine proper age)
  -Distributed worldwide - migrate to cooler waters in summer for feeding
• Cyclical movements vs. east to west
  A lot of genetic separation – little exchange between the north Atlantic and south Atlantic – leads to a good stock structure.

Question 32

Global Swordfish Production

Answer 32

-Fishery took off in the 1970’s
-North Atlantic swordfish was significantly overfished and lead to a crash in the 1990s
-Both NA and SA stocks are rebuilding. North is considered not overfished but the south still considered overfished.