Porbeagle

Question 1

Describe the relationship between the NW and NE Atlantic porbeagle (movement, genetics).

Answer 1

• No genetic difference between the populations, indicating some genetic exchange
• Only one documented instance of transatlantic migration
• Assess as different populations in some cases given lack of significant movement and different management regimes

Question 2

Describe the first record of transatlantic migration by porbeagle.

Answer 2

• 20 pound female first capture in Ireland

- Recaptured over 10 years later at over 200 pounds, 185 cm TL by Faroe Island vessel south of Grand Banks

Question 3

Describe the use of Irish waters by porbeagles.

Answer 3

• summer aggregation site for juveniles
• seasonal site fidelity for juveniles
• juveniles return to nearby locations between years
• evidence for size- or age-based spatial segregation

Question 4

high seas

Answer 4

international open waters

Question 5

Approximately what percentage of time is spent on high seas where they are largely unregulated and unmonitored?

Answer 5

Approximately 92% of time

Question 6

regional fisheries management organizations (RFMOs)

Answer 6

quai-cooperative alliances among countries that agree to work together toward a common goal
-ex: ICCAT

Question 7

When are spatial or seasonal fishery closures not effective?

Answer 7

when the target species and bycatch species share the similar habitat and prey items

Question 8

What fishery accounts for the most shark bycatch?

Answer 8

Pelagic longline fisheries

Question 9

How was overall mortality estimated by Campana et al. 2016?

Answer 9

sum of PRM for injured and healthy sharks (weighted by the relative frequency of each category) plus frequency of dead sharks (capture mortalities)

Question 10

What was the hooking mortality of porbeagles in the PLL fishery estimated by Campana et al. 2016?

Answer 10

44%

Question 11

What was the PRM for healthy porbeagles caught in PLL fishery by Campana et al. 2016?

Answer 11

10%

Question 12

What was the PRM for injured porbeagles caught in PLL fishery by Campana et al. 2016?

Answer 12

75%

Question 13

What was the overall PRM for porbeagles in the PLL by Campana et al. 2016?

Answer 13

27.2%

Question 14

Which species had the highest total fishing mortality (mako, blue, porbeagle) by Campana et al. 2016?

Answer 14

porbeagle

Question 15

What was the total fishing mortality for porbeagles in PLL fishery by Campana et al. 2016?

Answer 15

59.1%

Question 16

Why might porbeagles be most effected by PLL fishing in Campana et al. 2016?

Answer 16

• lamnids have high MR and high O2 requirements

- reduced ability to ram ventilate while hooked may not provide enough O2

Question 17

What was the seasonal migration of mature female porbeagles in the southern hemisphere (Francis et al. 2015)?

Answer 17

• moved to lower latitudes during winter and spring and higher latitudes during summer
• hypothesized to have reproductive source

Question 18

Explain the vertical movement pattern of porbeagles in the southern hemisphere (Francis et al. 2015)?

Answer 18

Diel vertical migration

• dive deeper during the day
• diel vertical migration less consistent when in shallower waters above the continental shelf

Question 19

How did Francis et al. 2015 suggest the southern hemisphere could reduce porbeagle bycatch?

Answer 19

limit PLL fishing to daylight hours when porbeagles are too deep to be caught

Question 20

Describe the relationship between the N Atlantic and southern Hemisphere porbeagle.

Answer 20

• genetically and biologically different
• southern Hemisphere population grows smaller, slower, and is longer-lived
• tropics at low latitudes may be a thermal barrier to population mixing

Question 21

What is the male size at maturity in NW Atlantic (Jensen et al. 2002)?

Answer 21

• between 162-185 cm FL

- 174 cm FL is size at 50% maturity

Question 22

What is the male age at maturity for the NW Atlantic (Jensen et al. 2002)?

Answer 22

8 years

Question 23

What is the female size at maturity in NW Atlantic (Jensen et al. 2002)?

Answer 23

• between 210-230 cm FL

- 218 cm FL is size at 50% maturity

Question 24

What is the female age at maturity in NW Atlantic (Jensen et al. 2002)?

Answer 24

13 years

Question 25

When is the expected mating season in the NW Atlantic (Jensen et al. 2002)?

Answer 25

Fall (September-November)

Question 26

When is the expected pupping season in the NW Atlantic (Jensen et al. 2002)?

Answer 26

Spring (April-June)

Question 27

What is the average litter size in the NW Atlantic (Jensen et al. 2002)?

Answer 27

4 pups (range 3-6)

Question 28

What did Jensen et al. (2002) suggested the reproductive cycle was in the NW Atlantic? Why

Answer 28

1 year

-most/all females were reproductively active

Question 29

How long is gestation in the NW Atlantic (Jensen et al. 2002)?

Answer 29

8-9 months

Question 30

What is the geographic range of porbeagles in the NW Atlantic?

Answer 30

Flemish Cap and Grand Banks to GOM (rarely south to NJ) and the Sargasso Sea

Question 31

What was the size at 50% maturity for males based on in the NW Atlantic (Jensen et al. 2002)?

Answer 31

clasper condition

Question 32

What was the depth range of porbeagles in the NE Atlantic during the winter (Saunders et al. 2011)?

Answer 32

0-700 m

Question 33

What was the temp range of porbeagles in the winter in the NE Atlantic (Saunders et al. 2011)?

Answer 33

9-17C

Question 34

Describe the vertical movement behaviors in the NE Atlantic winter (Saunders et al. 2011).

Answer 34

• inter-individual variation
• shallower at night than day
• transition in diving behavior when moved off shelf

Question 35

Describe migration pattern of porbeagles in winter in NE Atlantic (Saunders et al. 2011).

Answer 35

Located at shelf break or off shelf areas during autumn and winter, some individuals migrate south

Question 36

What may drive residency behavior in porbeagles?

Answer 36

High localized food availability

Question 37

What might drive migrations of porbeagles?

Answer 37

• searching for better feeding environment
• searching for mates
• gestation grounds

Question 38

How does vertical movement change when porbeagles move off the shelf?

Answer 38

stay deeper in the water column and rarely come to surface

Question 39

What could be the driver of diel vertical migration for porbeagles?

Answer 39

distribution of planktivorous fish that feed on diel vertically migrating zooplankton

Question 40

What was the size range of porbeagles tagged by Skomal et al. 2021?

Answer 40

128-154 cm FL

Question 41

Describe the horizontal migration of juvenile porbeagles in the NW Atlantic by Skomal et al. 2021.

Answer 41

Shelf oriented in summer and fall with more offshore movement in winter. Started to move back onto the shelf in Spring.

Question 42

What was the temperature range of porbeagles tagged by Skomal et al. 2021?

Answer 42

2-26C but 97% of time spent between 6-20C

Question 43

Describe the seasonal vertical movement patterns of porbeagles tagged by Skomal et al. 2021.

Answer 43

• Shallower distribution when on shelf with less pattern
• Diel vertical migration when offshore, some stayed deeper than 200 m (when in warm waters of Gulf Stream), others stayed above 200 m (when north of Gulf Strem)

Question 44

What factors are suspected to drive juvenile porbeagle seasonal horizontal and vertical movements in NW Atlantic (Skomal et al. 2021)?

Answer 44

• foraging behavior mediated by temperature

- although they have broad thermal tolerance, likely movements driven by optimal temperature range

Question 45

Why should the western and eastern North Atlantic porbeagle be managed as two separate stocks when they are genetically related?

Answer 45

• migration rates are low (2-12 individuals per year) enough that recruitment recovery from the other side of the ocean would not likely occur
• a much higher number of individuals migrating would be required to promote recovery of a depleted stock