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Biology 4663: Advanced Elasmobranch Studies > Topic 7: Sharks of The Open Ocean Conservation and Research > Flashcards

Topic 7: Sharks of The Open Ocean Conservation and Research Flashcards

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1
Q

There are fewer shark species in the ____.

A
  • open oceans
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2
Q

Open ocean sharks produce larger/smaller litters in comparison to costal species?

A
  • larger
    L> adaptation to scarce/patchy food sources vs a steady source in costal areas
    **larger the shark = larger litter
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3
Q

Apex predators are mostly sharks in the open ocean or costal waters?

A
  • open ocean
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4
Q

Open ocean sharks are the most common??

A
  • bycatch in fisheries (tuna long lining etc) lack of reliable catch data ( some nations have observers on the boat not all though!! not generalizable due to not every boat having an observer…. )
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5
Q

Open ocean sharks are rapidly increasing or decreasing in numbers? Why?

A
  • decreasing
    L> overfished…..
    *** one of the reasons people have turned to finning shakes is because they have over fished all other fishes….
    L>illegal to rbign fins into port without the body!! BUT o international regulations in open waters where the open ocean sharks are!
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6
Q

What are the main open ocean sharks that are at risk for finning?

A
  • Threshers
  • makos
  • salmon
  • porbeagle
  • silky
  • oceanic whitetip
  • blue
  • pelagic stingray
  • *lamnids: mako, salmon and porbeagle !
  • *pelagic stingray is not used in finning but is a big by catch !( it is pelagic vs being benthic which all other rays are)
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7
Q

Oceanic Whitetip is primarily an ___ ocean shark BUT can be found??? It is the first to be found near what? along with what other species of shark?

A
  • open
  • near islands
  • sea disasters
  • blue shark
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8
Q

Explain the state of historic shark populations!

  • Hammerheads
  • white sharks
  • tiger sharks
  • grey sharks
  • thresher sharks
  • blue sharks
  • mako sharks
  • oceanic whitetip
A
  • 89% gone
  • 79% gone
  • 65% gone
  • up to 83% gone
  • 80% gone
  • 60% gone
  • 5% gone
  • 70% gone
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9
Q

Shark fin trade alone:

  • up to almost __ blue sharks killed
  • up to ___ silky sharks killed
  • over a ____ oceanic whitetips
  • a ____ makos
  • almost ____ threshers
  • *per year!
A
  • 16 million
  • 2 million
  • a million
  • a million
  • 4 million
    • blue and silly = most plentiful open ocean sharks
    • huge waste of meat
  • o one is against fish if it is in usstaibable fashion etc
  • pst of these become bait (Minus their fins)
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10
Q

How many species of sharks and rays have gone extinct in the last 300 years due to over exploitation?

A

32

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11
Q

Smooth blacktip shark found ?

A
  • market in Yemen in 1902 but not identified until 1985
    • in 2008 found in Kuwait market
  • *no idea about population size in open ocean sharks
  • extinction is from a human interaction
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12
Q

Sharks are at risk for extinction due to?

A

life history strategies which low reproductive rates and long time to maturity!
L> over fishing eliminates them before they could mate

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13
Q

Give the life history traits of open ocean sharks!

A
  • litter size
  • birth size
  • gestation period
  • related migrations
  • maturity size and age
  • type of development
  • *these make them more at risk for over fishing!
  • reproductive mode is very important in terms of conservation
  • *development is another big issue with conservation o a shark
  • *Video: tiger beach…no clue they they are there…maybe a cleaning station…shrimp do this?
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14
Q

What are the modes of reproduction?

A
  • oviparous : egg deposits
  • viviparous : live birth
  • Aplacental viviparity with oophagy
    L> all lamniforms
    L> eggs produced with yolk
    L> once yolk depleted, embryo hatch and feed on eggs
    L> yolk stomach (distend
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15
Q

Whats the average litter size of porbeagles?

A

four

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16
Q

Modes of Reproduction:

- Placental vivparity?

A
  • requiem sharks
  • ova ovulated rom single functional ovary and are nourished by yolk
  • when yolk depleted, empty yolk sac forms a placenta like connection to maternal uterine wall
  • nutrient and gas exchange proved
  • new borns retain a faint umbilical scar

**mother may eat the newborns if they do not move up in the food chain quick enough
L> hormone is produced that suppresses feeding in mother
L> stress from trying to catch a pregnant shake can bring on birth
**mostly from fisher data
** a lot of sharks a specially blue sharks will abort a litter because of stress

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17
Q

Average litter of a lemon shark?

A
  • 9 pups
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18
Q

Modes of reproduction:

- Aplacental viviparity with trophonemata ?

A
  • pelagic stingray
  • similar to other stingrays
  • eggs produced in left ovary and move into left uterus
  • egg capsule ruptures and embryo nourished by elk
  • once depleted, female’s uterus forms fingerlike projections that extend into the lumen of the uterus
  • rich nutritious fluid called histotroph produced (uterine milk)
    L> bathed in fluid to ingested or absorb
    ** don’t know much about it but they assume it is similar to other stingrays… difference: once the yolk is depleted it comes out of the capsule but the female uterus ford fingerlike projections (trophonemata) secrete histotroph!
    ** three types found in open ocean
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19
Q

All pelagic species exhibit what reproduction mode??

A
  • viviparous mode
  • unsuitable in open ocean ( eggs would sink and may not survive the pressure or drift off to somewhere else…viviparous makes roe sense in open ocean!)
  • all have low reproductive raters but higher than costal one s
  • lower birth size relative to adult size
  • growth rate slower than coastal species
    L> costal species have larger pups and faster growth rates bc there are more predators in costal areas
20
Q

Similarities among pelagic lamniforms and carcharhinids suggests habitat is a ___.

A
  • strong selection force on reproduction
    L> costal has higher food and predators
    L> more selection pressure to produce larger and faster growing young
  • open ocean, limited resources and dispersal (need to travel great distances)
21
Q

What are the three local Canadian sharks?

A
  • Porbeagle shark
  • blue shark
    -mako shark
    ** targeted for recreational, commercial and by catch! Shark derby’s as well!
  • DFO sanctions them
  • Ecology action centre
  • World wildlife fund
    – tagged sharks tend tos survive better but you are also taking better care..
  • catches have been declining but most tend to be blue sharks!
    L> they are the trophy sharks since mako’s have been fished way over and beyond!
    *derbys = mostly local tourism…not generating a lot of obey
22
Q

The Biology and Ecology of the Porbeagle Shark:

- scientific name?

A
  • lamna nasus
23
Q

The Biology and Ecology of the Porbeagle Shark:

- feed on?

A
  • small schooling fishes such as herring, mackerels, flounders, hakes and cod, small sharks and squid!
24
Q

The Biology and Ecology of the Porbeagle Shark:

- use to be attacked by ___ but now its ___

A
  • direct fisheries

- by catch

25
Q

The Biology and Ecology of the Porbeagle Shark:

- Atlantic population?

A

** populations in the atlantic do not seem to mix! so there are different separate populations (west and east)

26
Q

The Biology and Ecology of the Porbeagle Shark:

- Size and appearance?

A
  • max length: 3m (10-12ft)
  • avg length: 1.5-1.8m (5-6ft)
  • avg weight: 135kg (300lbs)
  • max weight: over 225kg (500lbs)
  • no one really knows the origin of its name
    L> very elongated rostrum
  • very veracious hunters and fast le bagels
    **12fr= prob does not exist due to over fishing
  • avg length in bay of fundy = 7-8ft
    **the ones that come into the bay seem to be more robust and heavier vs open ocean which may be due to the amount of food here…other areas have a longer lifespan
27
Q 
The Biology and Ecology of the Porbeagle Shark:
- Life History:
L> reproduction mode?
L>gestation?
L> litter size? 
L> birth location 
L> reach maturity at?(male vs female) 
L>mate when?
L> life span?
A
  • ovoviviparous in which eggs hatch inside mother
  • 8-9 months(suspected…maybe they reproduce every two years? reproduction cycle may be 1-2 years therefore slow at it)
  • 4 pups born ( 68-80cm in length)
  • swim to Sargasso Sea (south of Bermuda …very warm water which goes against what we believed them to inhabit BUT they got to great depths there where the water would be cooler) to give birth
  • reach maturity at about 2.32-2.59 m for females in Northern hemisphere, shorter in souther hemisphere (~13 years)
  • males about 1.65-2.07m in NW atlantic (~8 years)
  • mate in autumn and winter and give birth in spring/summer
  • may live for 45 years
  • *anything over 7ft= reproducing maturity
28
Q

The Biology and Ecology of the Porbeagle Shark:

- do we ever see bit marks on females in bay of fundy?

A
  • nope …indicating they have’t mated yet
29
Q

The Biology and Ecology of the Porbeagle Shark:

- are we sure about the life span of 45 years?

A
  • no….staining the vertebrae which indicates this…cannot keep them in captivity so we can’t measure them to a newborn!
30
Q

The Biology and Ecology of the Porbeagle Shark:

- can their reproduction rate keep up with over fishing?

A
  • no it may not be able to
31
Q

The Biology and Ecology of the Porbeagle Shark:

- temperature of water they live in usually?

A

5-12 C (only sea surface temp

32
Q

The Biology and Ecology of the Porbeagle Shark:

- tags are all provided by?

A

commercial fisheries not for cience its for fisheries

33
Q

The Biology and Ecology of the Porbeagle Shark:
- Vulnerable to overfishing:
L> Norwegians?

A
  • targeted them and stock collapsed in North Atlantic in 1950s and western North Atlantic in the 1960s
  • *devestated the population
34
Q

The Biology and Ecology of the Porbeagle Shark:
- Vulnerable to overfishing:
L> Norwegians targeted them and stock collapsed in North Atlantic in 1950s and western North Atlantic in the 1960s:
- less than - of virgin biomass ( of the pre 50’s pop)

A
  • 10-20%
35
Q

The Biology and Ecology of the Porbeagle Shark:
- Vulnerable to overfishing:
L> Norwegians targeted them and stock collapsed in North Atlantic in 1950s and western North Atlantic in the 1960s:
- Still fished ___ and ___ via___

A
  • directed and by catch tuna and swordfish)
36
Q

The Biology and Ecology of the Porbeagle Shark:
- Vulnerable to overfishing:
L> Norwegians targeted them and stock collapsed in North Atlantic in 1950s and western North Atlantic in the 1960s:
- has the population recovered?

A

no

37
Q

The Biology and Ecology of the Porbeagle Shark:
- Vulnerable to overfishing:
L> Norwegians targeted them and stock collapsed in North Atlantic in 1950s and western North Atlantic in the 1960s:
- risk status of species?

A
  • vulnerable worldwide, critically endangered in some parts: IUCN especially in Northern Atlantic!
38
Q

The Biology and Ecology of the Porbeagle Shark:
- Vulnerable to overfishing:
L> Norwegians targeted them and stock collapsed in North Atlantic in 1950s and western North Atlantic in the 1960s:
- DFO refuses to list under?

A

SARA= political (legal body in Canada)
L> no directed fisher since 2013(except for spiny dog fish)
-shows how inadequate their plan was
- expects it to recover so do not want to list it
- accepts 4% mortality rate but will take 100 years to recover
L> no body knows for sure how many are there…these numbers are based on traditional fishing biomass
**can catch and keep dead ones but most release live ones

39
Q

The Biology and Ecology of the Porbeagle Shark:
- Vulnerable to overfishing:
L> Norwegians targeted them and stock collapsed in North Atlantic in 1950s and western North Atlantic in the 1960s:
- Exploratory program?

A
  • to help find something else for people to fish
40
Q

The Biology and Ecology of the Porbeagle Shark:

- Norwegians took over ___ metric tons of fish and decimated the population. Why did they give up?

A
  • 8060 metric tons

- none left! it is o longer viable

41
Q

The Biology and Ecology of the Porbeagle Shark:

- In response to fishing, age at maturity declined/increased in both sexes, more in___.

A
  • declined
  • females
  • *reproductive maturity came quicker!
42
Q

The Biology and Ecology of the Porbeagle Shark:
- In response to fishing, age at maturity declined in both sexes, more in females. length at maturity declined in ___ but not in ___.

A
  • males
  • females
  • *fished the larger animals…but caused them good increase in size..therefore reproduction success came to be an issue..so they fished the young ones to keep the big ones reproducing
43
Q

The Biology and Ecology of the Porbeagle Shark:
Satellite Tags:
- revealed possible?

A

pupping grounds

    • stay 500 m under surface t avoid warm water!
  • *where it was tagged and where it travelled= tags info
44
Q

The Biology and Ecology of the Porbeagle Shark:

  • Research in the bay of fundy:
  • Figure 2: Graphs representing the daily depth averages for the four categories of dawn(orange), day (yellow), dusk(red) and night (blue) with standard error bars for each of the four tags 17(a), 18(b), 19(c) and 22(d). Explain graph.
A
  • storm cloud boat: 9 knots
  • st. martins
  • average depths they went
  • up to 900 ft
  • spent a lot of time at depths in 400-500ft deep these sharks tend to spend a lot of time under the water and not at the surface: deciding factor for that type of tag to use on each shark!
    **four individual sharks
  • tags are only on for thirty days
  • temperature
  • speed etc
    >measured these
45
Q

The Biology and Ecology of the Porbeagle Shark:
- Research in the bay of fundy:
_ time they (tags) stayed on the sharks (tags)

A
  • temp range in C
  • gave a profile of the sharks and what they are doing
  • cyclic pattern for some of them
  • certain ays= more active than other s
  • second one: down to 1200ft…these tags do not monitor location so we cannot plot where it actually was…new tags do! what is survival rates of those with it on? all four tags on…all four released…all four survived…one survived for 2 years prior to being tangled up in US
46
Q

The Biology and Ecology of the Porbeagle Shark:
- Research in the bay of fundy:
L> Figure: 6 Average depths for day (yellow0 and night ( black) for 24 hours over the tagging period with associated temperatures during the day ( blue) and at night (purple) for the tag.

A
  • diving depth of one animal - major difference
  • dead? no because shark would sink to the bottom and satellite tag web released very prematurely from the shark being preyed on etc.
  • quite a ways down the water column
    -Graph: fork length cm
  • vertebral age
    L> length increased with age
    L> females are slightly larger
    L> growth rate..ti taper soft once they get to a certain age…around reproductive maturity females the GR slows down…males are not so long after!
    **probably for getting up in the food chain quick as to not be preyed n.

Biology 4663: Advanced Elasmobranch Studies (11 decks)

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