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Inter. J. of Marine Science 2012, Vol.2, No.4, 24-30
http://ijms.sophiapublisher.com
24
Research Report Open Access
Estimation of Important Reproductive Parameters for Management of the
Shoemaker Spinefoot Rabbitfish (
Siganus sutor
) in Southern Kenya
Simon Agembe
Kenya Marine and Fisheries Research Institute, P. O. Box 1881 Kisumu, Kenya
Corresponding author email:
agembesimon@yahoo.com;
Authors
International Journal of Marine Science, 2012, Vol.2, No.4 doi: 10.5376/ijms.2012.02.0004
Received: 11 Sep., 2012
Accepted: 17 Sep., 2012
Published: 19 Sep., 2012
This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any
medium, provided the original work is properly cited.
Preferred citation for this article:
Agembe, 2012, Estimation of Important Reproductive Parameters for Management of the Shoemaker Spinefoot Rabbitfish (
Siganus sutor
) in Southern Kenya,
International Journal of Marine Science, Vol.2, No.4: 24-30 (doi: 10.5376/ijms.2012.02.0004)
Abstract
The Shoemaker spinefoot,
Siganus sutor,
is a member of the family Siganidae, commonly known as rabbitfish. Many
demersal fish populations in the Kenyan waters are heavily exploited, and fishing effort may be above optimum levels for some
species. This study was aimed at determining missing parameters on spawning periodicity and maturity of
S. sutor
for the Kenyan
south coast area of Msambweni, complementing a suite of parallel studies on spawning aggregation based fisheries for this species. A
total of 376 samples were collected over 12 months, including 85 that were collected over four lunar phases in November and
December 2010. Monthly GSI showed two distinct peaks, one in June and July and one in November and January, suggested two
distinct spawning periods within the year. The highest GSI was recorded in November while the lowest values occurred in April
August and September
.
A lunar pattern in ovarian development stage was seen with the highest proportion of ripe ovaries (RI)
observed in the full moon phase, whereas running ripe (RR) or hydrated ovaries dominated samples in the last quarter. Imminent
spawning was confirmed by the presence of hydrated oocytes and post ovulatory follicles, observed primarily during the last quarter
and to a lesser extent during full moon. GSI value Kruskal-Wallis test showed significant differences in GSI between moon phases
(p<0.05). In conclusion, histological analysis of ovaries points to synchronous development of oocytes with moon phases, suggest
that their release takes place over short period of time after the full moon.
Keywords
Shoemaker spinefoot rabbitfish (
Siganus sutor
); South coast of Kenya; Reproductive parameters; Histology; Lunar
phase
Background
The Shoemaker spinefoot,
Siganus sutor
(Figure 1)
,
is
a member of the family Siganidae, commonly known
as rabbitfish. The family is widely distributed in the
Indian Ocean region (Lam, 1974; Randall, 1995) and
is generally regarded as good food fishes in spite of
their relatively small size. Woodland (1990) has described
Figure 1 Illustration of
Siganus sutor
(Source: Woodland, 1984)
13 siganid species that occur in the western Indian
ocean (WIO), including the endemic
S. sutor
. It occurs
in coastal waters to a depth of at least 40 m and is
important to artisanal and commercial fisheries. The
species is caught with a variety of fishing gears
(Woodland, 1984).
Many demersal fish populations in the Kenyan waters
are heavily exploited, and fishing effort may be above
optimum levels for some species (Kaunda-Arara et al.,
2003; McClanahan and Omukoto, 2011). While
S.
sutor
constitutes one of the most commercially
important demersal fish resources in the country (de
Souza, 1988), information on stock status is lacking
and fisheries are not explicitly managed for this
species. Knowledge of important reproductive parameters,
such as the periodicity of manner of spawning can
support management efforts aimed at protecting critical