Summary of Research on Spiny Dogfish in North Carolina by Rulifson and Colleagues, 19972003

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Summary of Research on Spiny Dogfish in North
Carolina by Rulifson and Colleagues, 1997-2003

• Mark-recapture, with population estimate for
  1997-2000 exploitable stock.
• Population estimate for spiny dogfish south of
  Cape Hatteras, NC during winter 1999 using area
  swept method.
• Biological characterization of overwintering
  dogfish north and south of Cape Hatteras, 1998-99.

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Spiny Dogfish, Squalus acanthias
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Spiny Dogfish Tagging Studies15,106 over 6-7
years

• Hickman et al. (2000)
• Thorpe and Beresoff (2000)
• Rulifson et al. (2000)
• SEAMAP Winter Tagging Cruises
• 1997, 1998, 1999, 2000, 2002, 2003
• Canada Nova Scotia 1996

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16th Annual Cooperative Winter Tagging Cruise
Cooperators

• U.S. Fish and Wildlife Service
• NOAA Fisheries
• Atlantic States Marine Fisheries Commission
  (ASMFC)
• NC Division of Marine Fisheries
• MD Department of Natural Resources
• South Atlantic Fisheries Management Council
• East Carolina University

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R/V Oregon II

• Owned by NOAA
• Commissioned in 1967
• 170 ft. long, 34 ft wide, 14 ft draft.
• 950 gross tons
• 17-18 Crew
• 12 Scientists

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Internal anchor tag
Single-barb dart tag with canula
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2003-Spiny Dogfish
8,940 measured, sexed
2,986 tagged released
(33.4)
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Witnessing the birth of a spiny dogfish pup
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Recaptures as a function of distance from NC
tagging sites (through 2000)
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Distance from NC Release Site vs Days at Large
Longest time for at-large is currently 2,350 days
from Canada release (96) and recapture (03)
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Recaptures by Lat.-Long.
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Recapture Mode

• Gill net 73
• 7.0 inch (10)
• 6.5 inch (35)
• 6.0 inch (35)
• 4 3/8 inch
• 4.0 inch
• 3 inch
• croaker net

• Trawl 11.1
• Rod and reel 7.4
• Longline 6.2
• Handline 1.2
• Dropnet 1.2

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Release Mode Recapture Rate
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US East Coast Overwintering Release Sites
Figure 1. Mark and release locations of spiny
dogfish captured off the North Carolina Outer
Banks during the 1997-98 and 1998-99 winter
commercial fishing seasons. The range of Seamap
Cruises in 1997 and 1998 are marked with C97-1
and C97-2, and C98-1 and C98-2, respectively and
fish were caught by trawl. Fish collected during
the FRG studies were collected by sink gillnet
(red-lined area).
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Scientific Sink Gillnet LocationsWinters 1997-8,
1998-9
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Spiny Dogfish Population Estimate Cape
Hatteras to Cape Fear, NC (Newman, Moore, and
Rulifson 2000)

• Sonar and Loran (GPS) survey to identify
  aggregations of spiny dogfish.
• Experimental gillnets deployed for 45 minutes
  within the aggregation.
• Outline of aggregation marked with Loran
  coordinates.

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Area Swept Method Using Scientific Gill Net Sets
Figure 4. Area of a spiny dogfish aggregation
located in Raleigh Bay during Set 8, between Core
Banks and Cape Lookout Shoals, March 10, 1999.
Estimated area 15,138.49 hec scale 1458,824.
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Figure 5. Area of a spiny dogfish aggregation
located in Long Bay during Set 2, between Frying
Pan Shoals and Shalotte Inlet, February 16, 1999.
Estimated area 1,634.22 hec scale 1365,000.
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Figure 6. Area of spiny dogfish aggregation
located in Onslow Bay during Set 4, between
Topsail Island and Carolina Beach Inlet,
February 18, 1999. Estimated area 30,521.47
hec scale 1445,462.
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Figure 7. Area of a spiny dogfish aggregation
located in Onslow Bay during Set 5, between
Beaufort Inlet and Bogue Inlet, February 19,
1999. Estimated area 5,505.42 hec scale
1279,683.
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Assumptions

• All nets fished at 100 efficiency
• All nets were set for approximately the same
  time
• Dogfish were uniformly distributed within the
  cluster
• Fish were not highly mobile during the study,
  remaining in the same general cluster area
• Only those dogfish within 25-50 yds (i.e., 5,000
  10,000 yds2) of the net were captured
• None of the fish captured and released was
  recaptured in subsequent samples (i.e., 100
  bycatch mortality as per NMFS designation) and
• Estimated surface area of the dogfish aggregation
  accurately described the cluster size.
• Fish leaving from natural mortality and entering
  the commercial fishery were equal and stable
  during this period.

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Spiny Dogfish Population Size
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Dogfish Summary Data South of Cape Hatteras
 
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Dogfish Lengths South of Cape Hatteras
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Dogfish Reproductive Stage South of Cape Hatteras
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Bycatch in Scientific Sink Gillnets, Cape
Hatteras to SC
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Are the Overwintering Populations in North
Carolina North and South of Cape Hatteras two
Separate Populations, or One Extended Population?
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Population Size Class Structure
Hatteras-Kitty Hawk, 98-99
Hatteras-SC, Feb-Mar 1999
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Population Age Class Structure
Hatteras-Kitty Hawk, 98-99
Hatteras-SC, Feb-Mar 1999
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Von Bert Growth Estimations
Hatteras-Kitty Hawk, 98-99
Hatteras-SC, Feb-Mar 1999
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Age to Maturity
Hatteras-Kitty Hawk, 98-99
Hatteras-SC, Feb-Mar 1999
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Fecundity
Hatteras-Kitty Hawk, 98-99
Hatteras-SC, Feb-Mar 1999
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Supporting Mark-Recapture Information

• Dogfish tagged off Cape Hatteras to Kitty Hawk
  and north have been recaptured at the northern
  end of the range (Gulf of Maine).
• Dogfish tagged south of Cape Hatteras have been
  recaptured at the northern end of the range (Gulf
  of Maine).
• One dogfish tagged during SEAMAP cruise (north of
  Cape Hatteras) was recaptured near Wilmington
  (south of Cape Hatteras)

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Spring migration, summer habitat
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Fall migration
Overwintering
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Second unit stock?
First unit stock
Unsampled extension

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Conclusions about North Carolina Dogfish

• Overwintering migratory stock of the U.S. Eastern
  Seaboard
• Dogfish aggregations south of Cape Hatteras
  represent a small but important part of the
  overwintering population
• Similar demographics
• Tag return confirmation
• Tag returns suggest that Cape Cod shelf area is
  the northern terminus for U.S. eastern Seaboard
  stock minimal mixing between U.S. and Canadian
  dogfish.