Ehrhardt and Deleveaux: Fishing capacity in a trap fishery for Panulirus argus 
189 
3 The monthly net revenue generated on a per 
trap day per trip basis under each of the 
above scenarios was estimated as the differ- 
ence between the monthly value of the catch 
per trap day per trip and the average cost of 
operating per trap day per trip based on the 
2003-04 census. Total revenue for the season 
was simply the product of the average revenue 
per trap day per trip and the average number 
of traps serviced per trip and the average 
number of trips per season. 
In the analyses pertaining to a fishery-wide scale 
the case scenarios were as follows: 
1 The catch per trap per trip referred to the fol- 
lowing three conditions: if fishing took place 
during the season with the highest (1997- 
98), or the lowest (2001-02), stock abundance 
during the TCP, or with the stock abundance 
of the season just prior to the implementation 
of the TCP (1991-92), and 
2 The catchability coefficient condition resulted 
from the number of traps operated in the fish- 
ery that corresponded to the three CPUE 
scenarios expressed above. 
Year 
Figure t 
Number of traps under the Trap Certificate Program (O) and 
catchability coefficient trend (•) for spiny lobster (Panulirus 
argus) in the Florida fishery from 1991 to 2002. 
Thus, it was possible to use the value per kilogram 
landed per trap day per trip and the cost per trap day 
per trip data to simulate the financial consequences 
for a maximum range of catchability and abundance 
combinations. 
Results 
Trap catch efficiency 
The assumption that the trap catchability would increase 
with the reduction of traps used in the Florida lobster 
fishery was verified during the TCP (Fig. 1) The trap 
soaking time was found to vary throughout the fish- 
ing season, with an increasing trend as the fishing 
season progressed and local population abundance was 
depleted. The soaking time also varied among fishing 
seasons (Fig. 2) as a consequence of differences in sea- 
sonal abundance. Therefore, the catch per trap day per 
trip was standardized to the changing seasonal soak- 
ing time. For this purpose an average monthly soaking 
time was estimated for every month in each season from 
the records in the trip ticket database. The resulting 
CPUE was consequently the average catch in numbers 
per trap day per trip. The seasonal CPUEs are plotted 
in Figure 3 where a persistent pattern of stock deple- 
tion is observed. A consistent fit of the depletion model 
was obtained for most years (Fig. 3) when the monthly 
natural mortality rate (M) commonly used in Caribbean 
spiny lobster assessments (FAO, 2001) was 0.0317 (or 
0.38 annually). The overall fit resulted in a residual 
sum of squares (RSS) of 1.277. 
O) 
c 
cd 
O 
c n 
18 
16 
14 
12 
10 
8 
6 
4 
2 
0 
Aug 
• 1997-1998 Highest-abundance 
2001-2002 Lowest-abundance 
Sep Oct Nov Dec Jan Feb 
Fishing season 
O 
Mar 
Figure 2 
Average trap soaking time in number of days for fish- 
ing seasons with highest spiny lobster stock abundance 
(1997-98) (•) and lowest stock abundance (2001-02) (O) 
in the Florida fishery. 
The 1991-92 fishing season had a higher stock abun- 
dance than the 2001-02 fishing season (which actually 
had the lowest abundance observed during the study 
period). The catchability coefficients were lowest dur- 
ing the 1991-92 seasons when the number of traps op- 
erating in the fishery was at the highest level. Mean- 
while the highest catchability coefficient was found 
in the 2001-02 season when the fewest traps were 
used in the fishery. Figure 4 clearly shows a negative 
functional correlation between the historic trends in 
