This article provides a stock assessment for east coast
weakfish, including estimated total landings in 2000, preliminary
estimates for 2000, and additional statistics.
the Stock Assessment (PDF 619.0 KB)
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An update of the stock
assessment and status of
Florida east coast weakfish, Cynoscion regalis
Janaka A. de Silva and Robert G. Muller
Florida Fish and Wildlife Conservation Commission
Florida Marine Research Institute
St. Petersburg, FL
August 29, 2001
Estimated total landings of weakfish in 2000 were higher than
1999 (153,000 pounds vs. 134,000 pounds). The recreational harvest
accounted for 94% of landings and has increased both in number and
proportion since 1999, when it accounted for 87% of landings.
Preliminary estimates for 2000 indicate that the commercial
fishery harvested 9,360 pounds in 639 trips. Commercial weakfish
landings in 2000 were 47% lower than 1999 landings, with 37% fewer
trips being made in 2000.
In 2000, an estimated 161,161 weakfish, weighing 143,265 pounds
were harvested (Type A1+B1 +0.2B2) by recreational fishers. In
terms of weight, the recreational harvest of weakfish in 2000 was
the second highest during the last fifteen years. When comparing
2000 landings to 1999 by numbers of fish, the harvest was 13%
higher than 1999 and 23% higher in terms of weight. Using
standardized trips as an estimate of recreational effort, the
number of trips during which weakfish were harvested increased by
45% over 1999 estimates.
Based on the preliminary catch estimates, the total harvest of
weakfish in Florida was 1.20% of the 1999/2000 average coastwide
landings. However, given the variability associated with the
estimated recreational landings (represented by PSE) the estimate
of Florida's weakfish harvest is not likely to be significantly
different from the 1% de minimis criteria.
Examination of recreational length frequencies indicates that
the 12-inch minimum size that was implemented in 1994 has had
little effect on the size of fish landed. The average percentage of
weakfish less than 12 inches in the recreational sector prior to
the minimum size was 28% (CV = 54%) and 24% (CV = 66%) after its
implementation. For the commercial sector, an average of 30% of
weakfish (CV = 103%) were less than 12 inches before the 12-inch
minimum size was implemented and an average of 31% (CV = 70%) were
To evaluate the efficacy of the bag limit, recreational
intercepts were grouped into two time periods representing pre- and
post-regulations: 1982-1994 and 1995-2000. The standard bootstrap
model was run on intercepts from each of the periods. Based on the
results of the bag limit analysis, 4.4% of trips exceeded the 4
fish bag limit during the post-regulatory period. Furthermore, the
analysis also indicates that the bag limit has reduced the
recreational harvest by about 13%, which is about half of the
Estimates of weakfish fishing mortality rates (F) and population
size from 1986 to 2000 were made using a similar protocol to that
used in the 2000 assessment. For 2001, Integrated Catch-at-Age
Analysis which is a separable virtual population analysis was used.
While the general methodology used in the 2001 assessment was
similar to 2000, three changes were made in the data used in the
analysis. In addition, one of the assumptions made in the analysis
was also changed.
Population size estimates showed that the number of weakfish on
Florida's Atlantic coast increased from 803,610 in 1986 to
1,072,840 in 1993. From 1993, population estimates declined to a
low of 308,640 weakfish in 1996 during the period 1986-2000.
Population estimates in 1997 were 387,900 and increased to 594,520
fish in 2000.
From 1986 to 1993, estimates of fishing mortality rates (F) for
ages 1-5 were variable, fluctuating around an average F of 1.27 per
year. In 1994 the fishing mortality rate abruptly increased to 1.98
per year and has declined following the implementation of the 1995
Constitutional limit to net fishing, minimum size, and bag limit.
While estimates have varied since 1995, recent estimates of F for
1999 and 2000 were 1.21 per year (95% confidence interval
0.89-1.60) and 1.39 per year (95 % confidence interval 0.77-2.58)
respectively. While previous assessments indicated that fishing
mortality estimates for Florida weakfish had been below the yearly
ASMFC target values since 1996, this assessment indicates that the
2000 ASMFC target of 0.50 has been exceeded.
Comparing the population size and fishing mortality estimates
from the present assessment to those in the 2000 assessment
indicated that population estimates follow a similar trend.
However, for the terminal years in the analysis (1998 and 1999)
estimates based on the 2001 assessment indicate lower population
and higher fishing mortality estimates, particularly for 1999, than
do those in the 2000 assessment. Discrepancies in population
estimates and F values in the terminal year are most likely related
to the methodology, which is sensitive to terminal F values that
enable the analysis to be extended to incomplete cohorts, and the
model specifications used in the current analysis.
The primary area for improving the analysis is obtaining better
age information. While the recreational fishery for weakfish has
grown in importance and now accounts for 95% of the harvest, the
biological information that is used in the age analysis is derived
primarily from commercial sources. Weakfish for age analyses need
to be collected from all aspects of the fishery.
For other information:
assessments for finfish and invertebrate
Prior to July 1, 2004, the Fish and Wildlife Research
Institute was known as the Florida Marine Research Institute. The
institute name has not been changed in historical articles and
articles that directly reference work done by the Florida Marine