Maximum sustainable yield estimates of Ladypees, Sillago sihama (Forsskål), fishery in Pakistan using the ASPIC and CEDA packages

• Published in: Journal of Ocean University of China Vol. 11; no. 1; pp. 93 - 98
• Main Authors: Panhwar, Sher Khan, Liu, Qun, Khan, Fozia, Siddiqui, Pirzada J. A.
• Format: Journal Article
• Language: English
• Published: Heidelberg SP Science Press 01-03-2012; Springer Nature B.V
• Subjects: Biomass; Carrying capacity; Coefficient of variation; Doctor Forum; Earth and Environmental Science; Earth Sciences; Estuaries; Fish populations; Fisheries; Marine; Meteorology; Oceanography; Sillago sihama; Sustainability; Sustainable yield; ISW, Pakistan; CEDA; ASPIC; Pakistan; surplus production models
• ISSN: 1672-5182; 1993-5021; 1672-5174
• DOI: 10.1007/s11802-012-1880-3

Using surplus production model packages of ASPIC (a stock-production model incorporating covariates) and CEDA (Catch effort data analysis), we analyzed the catch and effort data of
Sillago sihama
fishery in Pakistan. ASPIC estimates the parameters of
MSY
(maximum sustainable yield),
F
msy
(fishing mortality),
q
(catchability coefficient),
K
(carrying capacity or unexploited biomass) and
B1/K
(maximum sustainable yield over initial biomass). The estimated non-bootstrapped value of MSY based on logistic was 598 t and that based on the Fox model was 415 t, which showed that the Fox model estimation was more conservative than that with the logistic model. The
R
2
with the logistic model (0.702) is larger than that with the Fox model (0.541), which indicates a better fit. The coefficient of variation (cv) of the estimated
MSY
was about 0.3, except for a larger value 88.87 and a smaller value of 0.173. In contrast to the ASPIC results, the
R
2
with the Fox model (0.651–0.692) was larger than that with the Schaefer model (0.435–0.567), indicating a better fit. The key parameters of CEDA are:
MSY, K, q
, and
r
(intrinsic growth), and the three error assumptions in using the models are normal, log normal and gamma. Parameter estimates from the Schaefer and Pella-Tomlinson models were similar. The
MSY
estimations from the above two models were 398 t, 549 t and 398 t for normal, log-normal and gamma error distributions, respectively. The
MSY
estimates from the Fox model were 381 t, 366 t and 366 t for the above three error assumptions, respectively. The Fox model estimates were smaller than those for the Schaefer and the Pella-Tomlinson models. In the light of the
MSY
estimations of 415 t from ASPIC for the Fox model and 381 t from CEDA for the Fox model,
MSY
for
S. sihama
is about 400 t. As the catch in 2003 was 401 t, we would suggest the fishery should be kept at the current level. Production models used here depend on the assumption that CPUE (catch per unit effort) data used in the study can reliably quantify temporal variability in population abundance, hence the modeling results would be wrong if such an assumption is not met. Because the reliability of this CPUE data in indexing fish population abundance is unknown, we should be cautious with the interpretation and use of the derived population and management parameters.