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

1. 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.

2. Spiny Dogfish, Squalus acanthias

3. Spiny Dogfish Tagging Studies~15,106 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

4. 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

5. 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

6. Internal anchor tag Single-barb dart tag with canula

7. 2003-Spiny Dogfish 8,940 measured, sexed 2,986 tagged & released (33.4%)

8. Witnessing the birth of a spiny dogfish pup

9. Recaptures as a function of distance from NC tagging sites (through 2000)

10. 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)

11. Recaptures by Lat.-Long.

12. Recapture Mode • Trawl 11.1% • Rod and reel 7.4% • Longline 6.2% • Handline 1.2% • Dropnet 1.2% • 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”

13. Release Mode – Recapture Rate

14. 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).

15. Scientific Sink Gillnet LocationsWinters 1997-8, 1998-9

16. 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.

18. “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 = 1:458,824.

19. 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 = 1:365,000.

20. 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 = 1:445,462.

21. 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 = 1:279,683.

22. 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.

23. Spiny Dogfish Population Size

24. Dogfish Summary Data – South of Cape Hatteras

25. Dogfish Lengths South of Cape Hatteras

26. Dogfish Reproductive Stage South of Cape Hatteras

27. Bycatch in Scientific Sink Gillnets, Cape Hatteras to SC

28. Are the Overwintering Populations in North Carolina North and South of Cape Hatteras two Separate Populations, or One Extended Population?

29. Population Size Class Structure Hatteras-Kitty Hawk, 98-99 Hatteras-SC, Feb-Mar 1999

30. Population Age Class Structure Hatteras-Kitty Hawk, 98-99 Hatteras-SC, Feb-Mar 1999

31. Von Bert Growth Estimations Hatteras-Kitty Hawk, 98-99 Hatteras-SC, Feb-Mar 1999

32. Age to Maturity Hatteras-Kitty Hawk, 98-99 Hatteras-SC, Feb-Mar 1999

33. Fecundity Hatteras-Kitty Hawk, 98-99 Hatteras-SC, Feb-Mar 1999

34. 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)

35. Spring migration, summer habitat

36. Fall migration Overwintering

37. Second “unit stock”? First “unit stock” Unsampled extension

38. 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.