L17 - Marine Mammal Conservation - Tuna Dolphin

Question 1

purse seining (2)

Answer 1

1. setting net on tuna and dolphins in an attempt to catch tuna
   - synch the purse
2. backdown procedure - dolphins are released
   - requires experienced captain and crew

Question 2

history of the problem (5)

Answer 2

1. no mortality data prior to 1970
   - estimated 350,000-650,000/yr
2. before 1970, US 80% or mortality
3. MMPA 1972
4. 2 yr exemption to solve problem: gear and prodecure modifications
5. 1977 observers on all US boats

Question 3

inter-american tropical tuna commission (IATTC) 1979

Answer 3

conservation program to match US efforts

Question 4

the tuna-dolphin dispute (10)

Answer 4

1. 1986: observers reported mortality at 133,000/yr
2. US: required countries exporting tuna to follow their regulations
3. would allow ~2x US takes
4. 1994 only “dolphin-safe” tuna in US
5. implemented tuna embargo if not met
6. after 6 months, uncreased embargo to all fish
7. trade conflicts between US and Mexico, Ecuador, Venezuela, others
8. US largest market
9. dramatic impact on trade, especially for Mexico
10. panama declaration (1995): many countries agreed to mortality limits and embargo lifted

Question 5

current status: 2002 (4)

Answer 5

1. 91% of all sets mad dolphins=no mortality or serious injury
2. total mortality to less than 2000 (0.02% population)
3. national marine fisheries service - dolphin sets do not have significant adverse impact
4. tuna caught in sets with no dolphin mortality is “dolphin-safe”

Question 6

current status: 2004 (3)

Answer 6

1. earth island institute US humane society and others challenged decision
2. court ruling changed definition of “dolphin-safe”
3. no tuna caught on a trip where nets were intentionally set on dolphins and no dolphins killed or seriously injured

Question 7

types of tuna sets (3)

Answer 7

1. dolphin sets
2. school sets
3. log sets or fish aggregation devices

Question 8

school sites (2)

Answer 8

1. tuna don’t surface like dolphins

2. difficult to find schools over great distances

Question 9

fish aggregation devices (7)

Answer 9

1. drifting object
2. small fish
3. juvenile fish
4. small pelagic fish
5. tuna
6. broadbills (sailfish, marlin)
7. sharks, rays

Question 10

current dolphin status

Answer 10

1. population 15-35% initial size

2. low takes, no recovery?

Question 11

current dolphin ststus : hypotheses (5)

Answer 11

1. bycatch is higher than reported
2. ecological effects of removing tuna
3. effects of break up of school - increased predation by “black fish”
4. repeated chase impacts survival/reproduction
   - catches 1-50 times/yr
   - avg 8 times/yr
5. separation of mom and calf