Population demographics of southern flounder in the New River, North Carolina gill net fishery
- UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
- William E. Smith (Creator)
- Institution
- The University of North Carolina Wilmington (UNCW )
- Web Site: http://library.uncw.edu/
- Advisor
- Ken Pollock
Abstract: The North Carolina (NC) fishery for southern flounder (Paralichthys lethostigma)
is currently listed as overfished by the North Carolina Division of Marine Fisheries, and
in 2005 management changes were enacted in the fishery in order to achieve a 2005
reduction in fishing mortality. Virtual Population Analysis models are currently used to
assess fishing mortality (F) in the NC southern flounder stock, but direct estimates may
be more accurate. Direct estimates of F in the New River, NC gill net fishery for
southern flounder were obtained for years 2005 and 2006 using tag-returns and
accounting for return rate, tag retention, and mortality due to tagging. Annual estimates
of F and their probability distributions, F2005 = 1.02 (SE = 0.095) and F2006 = 1.54 (SE =
0.222), indicated a high probability that F attained the targeted fishing mortality of Ftarget
= 0.95 in 2005 and a very low probability (p=0.0068) that F attained the target in 2006 in
the New River gill net fishery. High interannual variability in F was found, which agrees
with recent stock assessments. The results suggest that under the current regulations, F
will potentially continue to exceed the target in some NC estuaries, and additional
management measures may be necessary in order to reduce F to the target in all systems
in which the fishery is executed.
Recoveries of previously tagged fish were used in a catch composition analysis of
the length frequency, size at age, and maturity of southern flounder harvested in the New
River gill net fishery, demonstrating the potential effects of the fishing strategy on longterm
yield. Examination of the length frequency distribution indicates that approximately
36% of the catch is composed of sub-legal southern flounder that are discarded, with
unknown consequences on mortality. It appears that the fishery is targeting age-1 southern flounder (88% total catch), and all age-0 and age-1 fish exhibited above average
growth for southern flounder in NC. 28% of females captured in the months previous to
the spawning season were distinguishable as mature, and approximately 19% of the catch
may have had the opportunity to spawn in the spawning season previous to their capture,
suggesting that much of the catch is immature. Recent evidence suggests that a high
removal rate of fast-growing, immature animals can have deleterious effects on long-term
yield in the fishery. Yield per recruit analysis and maturity schedules demonstrated that
delaying age at entry into the fishery until age-2 may potentially provide higher, more
stable yields that are robust to interannual variability in fishing mortality, while also
allowing more fish to spawn before becoming subject to the fishery.
Population demographics of southern flounder in the New River, North Carolina gill net fishery
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Additional Information
- Publication
- Thesis
- A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirement for the Degree of Masters of Science
- Language: English
- Date: 2009
- Keywords
- Southern flounder--North Carolina--New River, Southern flounder--North Carolina--Population, Flatfish fisheries--Environmental aspects--North Carolina--New River
- Subjects
- Southern flounder -- North Carolina -- New River
- Southern flounder -- North Carolina -- Population
- Flatfish fisheries -- Environmental aspects -- North Carolina -- New River