| Naga
- The *ICLARM Quarterly
Vol.
22, No. 3 (July - September 1999)
Fishbyte
(Fisheries Section of NTAFP)
Editorial
“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 (www.fishbase.org) 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 (www.ecopath.org)
and welcome more inputs from you.
G.
Silvestre and V. Christensen
*ICLARM
A
Collection of Empirical Relations for Use in
Ecological Modelling
T.
Brey Abstract
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: tbrey@awi-bremerhaven.de
Escalation
in Shrimp Production in the Sierra Leone Industrial
Fishery
P.A.T.
Showers
Abstract
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
Abstract
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: ecucalon@gu.pro.ec
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