Porbeagle Flashcards
(45 cards)
Describe the relationship between the NW and NE Atlantic porbeagle (movement, genetics).
- 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
Describe the first record of transatlantic migration by porbeagle.
- 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
Describe the use of Irish waters by porbeagles.
- 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
high seas
international open waters
Approximately what percentage of time is spent on high seas where they are largely unregulated and unmonitored?
Approximately 92% of time
regional fisheries management organizations (RFMOs)
quai-cooperative alliances among countries that agree to work together toward a common goal
-ex: ICCAT
When are spatial or seasonal fishery closures not effective?
when the target species and bycatch species share the similar habitat and prey items
What fishery accounts for the most shark bycatch?
Pelagic longline fisheries
How was overall mortality estimated by Campana et al. 2016?
sum of PRM for injured and healthy sharks (weighted by the relative frequency of each category) plus frequency of dead sharks (capture mortalities)
What was the hooking mortality of porbeagles in the PLL fishery estimated by Campana et al. 2016?
44%
What was the PRM for healthy porbeagles caught in PLL fishery by Campana et al. 2016?
10%
What was the PRM for injured porbeagles caught in PLL fishery by Campana et al. 2016?
75%
What was the overall PRM for porbeagles in the PLL by Campana et al. 2016?
27.2%
Which species had the highest total fishing mortality (mako, blue, porbeagle) by Campana et al. 2016?
porbeagle
What was the total fishing mortality for porbeagles in PLL fishery by Campana et al. 2016?
59.1%
Why might porbeagles be most effected by PLL fishing in Campana et al. 2016?
- lamnids have high MR and high O2 requirements
- reduced ability to ram ventilate while hooked may not provide enough O2
What was the seasonal migration of mature female porbeagles in the southern hemisphere (Francis et al. 2015)?
- moved to lower latitudes during winter and spring and higher latitudes during summer
- hypothesized to have reproductive source
Explain the vertical movement pattern of porbeagles in the southern hemisphere (Francis et al. 2015)?
Diel vertical migration
- dive deeper during the day
- diel vertical migration less consistent when in shallower waters above the continental shelf
How did Francis et al. 2015 suggest the southern hemisphere could reduce porbeagle bycatch?
limit PLL fishing to daylight hours when porbeagles are too deep to be caught
Describe the relationship between the N Atlantic and southern Hemisphere porbeagle.
- 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
What is the male size at maturity in NW Atlantic (Jensen et al. 2002)?
- between 162-185 cm FL
- 174 cm FL is size at 50% maturity
What is the male age at maturity for the NW Atlantic (Jensen et al. 2002)?
8 years
What is the female size at maturity in NW Atlantic (Jensen et al. 2002)?
- between 210-230 cm FL
- 218 cm FL is size at 50% maturity
What is the female age at maturity in NW Atlantic (Jensen et al. 2002)?
13 years
