Jones and Wells: Yield modeling for Pogonias cromis 
329 
ings (averaging 37,000 and 26,000 kg respectively), where- 
as New Jersey, Delaware, Maryland, North Carolina, South 
Carolina, and Georgia have average landings of less than 
18,000 kg. In contrast, between 1981 and 1994 recreation- 
al landings averaged 315,000 kg (693,000 pounds) I 2 * * * * * * ' 9 annu- 
ally, 300% higher than the commercial catch. Recreational 
landings north of Cape Hatteras vary from 0.4% to 78% of 
the annual East Coast recreational catch, reflecting varia- 
tions in abundance of older fish and in their seasonal mi- 
gration patterns. 
With its location at the northern end of the range, Ches- 
apeake Bay fisheries target black drum that are primar- 
ily old (26 yr), and large (108.4 cm; 22.1 kg) during a short 
season; most of the catches occur from April to June (Jones 
and Wells, 1998). Large fish enter the Bay in April and are 
caught by the commercial fishery with 33-cm stretch mesh 
anchored and drifted gill nets. Historically, the commercial 
market is local, and fillets and roe are a spring treat for 
residents of the eastern shore of Virginia and Maryland 
during April and May (Jones et al., 1990). Because of this 
limited market that becomes saturated, the price drops 
in late spring and commercial fishermen turn from black 
drum to pursue more profitable fishes. The recreational 
fishery usually begins and ends a month later than the 
commercial fishery, from May to June, and anglers target 
large trophy fish with hook and line. Although the recre- 
ational season is short, it occurs before more popular fish 
enter the Bay, and the fishery supports local business at 
that time. Thus, the black drum fishery is important to the 
economies of two of the poorest counties in Virginia, which 
are located on the eastern shore (Jones et al., 1990). 
In the mid-Atlantic region, the lack of accurate catch and 
effort data from the commercial and recreational black 
drum fisheries makes it difficult to evaluate whether the 
long-term fluctuations in population abundance and the 
current decline in abundance of citation-size fish result 
from natural patterns of dominant year classes or from ex- 
cess exploitation and subsequent population decline. Re- 
ports of catch and effort in the commercial fishery have 
been based, generally, on voluntary reporting. Likewise, the 
difficulty in sampling this short-season and charter-based 
recreational fishery has led to estimates of catch and effort 
that are characterized by extremely broad confidence lim- 
its. Even so, in response to the concerns of Virginia’s recre- 
ational anglers to supposed population decline, commercial 
harvest quotas were imposed on these fisheries in 1992 in 
the absence of any stock assessment ( Commonwealth of Vir- 
ginia, 1992, VMRC regulation 4 VAC 20-320-10 et seq.). 
Yield-per-recruit models can provide the benchmarks for 
assessing growth overfishing (Gulland, 1983; King, 1995). 
I ( continued ) Coastal Resources Division, One Conservation Way, 
Brunswick, GA 31523-8600. 
s Sutherland, D. 1995. 1979-94 Black drum commercial land- 
ings for Atlantic Coast states. Fisheries Statistics Division, 
National Marine Fisheries Service, 1315 East West Highway, 
Silver Spring, MD 20910. 
II Fisheries Statistics Division and Economics Division. 1996. 
Personal commun. Fisheries Statistics Div. and Economics 
Div., National Marine Fisheries Service, 1315 East West High- 
way, Silver Spring, MD 20910. 
Specifically, yield-per-recruit modeling provides reference 
points to theoretically maximize yield from a cohort ( F MAX ), 
or increase the number of trophy-size fish in the population. 
Because F MAX frequently results in unsustainable harvests, 
an ad hoc benchmark (F 01 ) is calculated to provide more 
conservative harvest recommendations. However as impor- 
tant as this modeling is to science-based management, no 
published application of yield-per-recuit models exists for 
black drum from the Chesapeake Bay region. In our study 
we used data from Chesapeake Bay (Jones and Wells, 1998) 
and Florida (Murphy and Taylor, 1989) to evaluate the effect 
of fishing mortality and age at first capture on yield-per- 
recruit models of these fish, especially for management in 
the Bay. Although more accurate stock assessments result 
when catch-age or age-structured models such as ADAPT 
are used, the absence of a time series of aged-catch data 
precludes their use for this fishery. Until such data become 
available, the results of yield-per-recruit models can be used 
now to determine whether regulations such as size limits, 
catch quotas, and effort limitations, which are already in ef- 
fect, are necessary to manage this fishery. 
Materials and methods 
Yield-per-recruit analysis 
The Beverton-Holt yield-per-recruit model (Beverton and 
Holt, 1957) was used to calculate yield-per-recruit curves 
following the formula 
Y / R - Fe 
T T -hKU -l u > 
w Y-Li 
^ F + M + nK 
( 1 ) 
where Y/R 
F 
M 
t c 
t r 
W,, 
*o 
K 
yield-per-recruit in weight (kg); 
instantaneous fishing mortality coefficient; 
instantaneous natural mortality coefficient; 
summation parameter ( C7 0 =l, U y =— 3, U 2 - 3, 
U 3 =- 1); 
mean age (years) at first capture; 
mean age (years) at recruitment to the 
fishing area; and 
asymptotic weight; 
hypothetical age the fish would be zero 
length; and 
the Brody growth coefficient. 
Computations were performed by using a modification of 
the computer program B-H3 available in the Basic Fisher- 
ies Science Programs package (Saila et al., 1988). Parame- 
ters used in these simulations are summarized in Table 1. 
The first two parameters, t Q and K, are derived from the 
von Bertalanffy growth equation for black drum (Jones 
and Wells, 1998): 
1, = 117.3(1- e" (nor "' +2:i ’). (2) 
Because fish aged 1-5 were not available in Chesapeake Bay, 
our estimate of K( 0.105) was smaller than that obtained by 
