* ICLARM is now known as WorldFish Center

Naga - The *ICLARM Quarterly
Vol. 22, No. 3 (July - September 1999)

Fishbyte (Fisheries Section of NTAFP)
“Progress in any field depends primarily on our ability to synthesize previous experience”. This is the opening remark from Hilborn and Liermann’s recent plea for meta-analysis in fisheries, published in a Beverton and Holt Jubilee (40 years young) special issue of Reviews in Fish Biology and Fisheries. Ray Hilborn and Martin Liermann emphasize that fisheries models should strive to incorporate experience and not simply ignore it as most often the case. They find comfort, however, in the pioneering compilations of Daniel Pauly on natural mortality, in Ram Myers and colleagues' stock-recruitment work, and they conclude that the most critical need for meta-analysis is availability of databases, citing FishBase ( as a good example. Another good example is given in this issue of FishByte. Tom Brey of AWI has for years been collecting and analyzing information on productivity of benthic invertebrates and his Opus Major from 1995 is indeed a gold mine for ecological modelers in need of reliable productivity estimates. We are happy to present a Brey potpourri of empirical relationships here. As ecological modeling is becoming more and more useful for fisheries research, the need for information on all aspects of aquatic life is increasing. Reflective of this is that we are including a variety of empirical relationships in the Ecopath with Ecosim software system ( and welcome more inputs from you.

G. Silvestre and V. Christensen

A Collection of Empirical Relations for Use in Ecological Modelling
T.  Brey

This study summarizes previously published and updated empirical relations for the estimation of production/biomass ratios in benthic invertebrates; of natural mortality in benthic invertebrates and finfish; and of respiration from production and vice versa in animal populations. A MS-EXCEL spreadsheet containing these equations is available from the author via Email. They are also included in the Ecopath with Ecosim software.

T. Brey is from the Alfred Wegener Institute for Polar and Marine Research, P.O. Box 120161, D-27576, Bremerhaven, Germany. E-mail:

Escalation in Shrimp Production in the Sierra Leone Industrial Fishery
P.A.T. Showers

Applying Tukey's jackknife method on MSY estimates from the surplus production models of Schaefer and Fox showed that the optimum yield for shrimps in industrial fishery in Sierra Leone is estimated at 2686.8 t with 15822 fishing days.  Annual catch for 1996 was 2788 t, indicating an escalation in exploitation which, if prolonged, could bring reduced productivity as experienced in the fishery some years ago.

P.A.T. Showers is from the Institute of Marine Biology and Oceanography, Fourah Bay College, University of Sierra Leone, Sierra Leone.

Growth and Length-Weight Parameters of Pacific Mackerel (Scomber japonicus) in the Gulf of Guayaquil, Ecuador
E. Cucalón-Zenck

The seasonally oscillating growth parameters and length-weight relationship for Scomber japonicus caught in the Gulf of Guayaquil, Ecuador, were determined based on length-frequency data from 1989 to 1996, using the FiSAT software package of Gayanilo et al. (1996). Estimates of growth parameters are in general agreement with previous studies on the same species. Results also imply that the growth of S. japonicus slows down during the cold season by approximately 50% with respect to the average growth. The mean value of the power b is significantly larger than 3, indicating that the model of allometric growth should be used for the length-weight relationship and calculation of the condition factor.

E. Cucalón-Zenck is from Oceanografia y Pesca Consultores (Fisheries and Oceanography Consulting)PO Box 09-01-4382, Guayaquil, Ecuador. E-mail:

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