5
2016); 2.29 (Tserpes and Tsimenides, 2001) and 2.10
(Torcu-Koc et al., 2004), 2.23 (Ilhan et al., 2010) in the
Western Mediterranean. This would indicate that S. cabrilla
of the central coast of Algeria grows faster than in the other
regions. As for variable minimum and maximum lengths
in the different areas, fluctuations in growth parameters
(L ∞ , K) can be explained by variations in the environmental
and the ecological factors (temperature, mortality and
food availability) from one area to another (Korcu-Koc
et al., 2004).
We must consider that different techniques have
been used in the regions studied (Bouain, 1983; Tserpes
and Tsimenides, 2001; Torcu-Koc et al., 2004; Ilhan
et al., 2010; Gordo et al., 2016). The methodology used
in each region also explains the differences between the
obtained results.
The allometry coefficient “b” was 2.963. Similar
results have been reported by Ilhan et al. (2010) and
Moutopoulos and Stergion (2002) in Aegean Sea, by
Gordo et al. (2016) in Portugal and by Rachedi and Dahel
(2019) in the Gulf of Annaba. Unlike those obtained by
Torcu-Koc et al. (2004) in Edremit Bay and by Goncalves
et al. (1997) in Portugal, which showed negative
allometric growth. Ozvarol (2014) in the Gulf of Antalya
presented positive allometric growth for the species
(Table 2). In general, the b parameter is subject to changes
due to sample size, environmental factors and seasonality
(Froese, 2006).
Growth and mortality estimations are important for
understanding population dynamics (Ralston and Williams,
1988). We estimated the natural (M) and total mortality
(Z) at 0.43 and 2.63 yr
-1
, respectively. The estimated M
value was close to the value obtained in other regions.
Gordo et al. (2016) reported a total mortality rate between
0.44 and 0.48 yr
-1
in the eastern Atlantic (Portugal),
Tserpes and Tsimenides (2001) reported 0.35 yr
-1
at the Cretan Shelf (Greece) and Torcu-Koc et al. (2004)
obtained 0.32 yr
-1
in Edremit Bay (Turkey). On the other
hand, the value of natural mortality (M = 0.81 yr
-1
)
obtained by Rachedi and Dahel (2019) in the Gulf of
Annaba was higher than the value obtained in this study.
In fact, according to Sparre and Venema (1996) values of
natural mortality coefficients for the same species may
be different in distinct areas, depending on the density of
predators and competitors whose abundance is otherwise
influenced by fishing activities. Even small changes in
growth parameters could seriously affect the calculated
mortality (Tserpes and Tsimenides, 2001).
The resulting exploitation rate, E = 0.84, is higher
than the optimal value (0.5) mentioned by Gulland (1971).
Hence, the comber stock of this species is overexploited
in the study region. This situation could have an impact
on recruitment if individuals are caught during the
reproduction period (Sossoukpe et al., 2013).
Our study was carried out in order to estimate the
growth and the exploitation parameters of the comber
S. cabrilla from Bou Ismail Bay, Algeria. The determined
parameters are necessary for the stock assessment and
management of this species in the central coast of Algeria.
The inshore fishery for the comber S. cabrilla in Bou
Ismail Bay targets mainly individuals between 14 and
16 cm in total length (59.95%), while larger (24-26 cm)
and smaller individuals (9-11 cm) are caught in smaller
proportions (1.66%). The length-weight relationship of
this species shows that growth in length and weight is
isometric (a = 0.0119, b = 2.96, r² = 0.93). The calculated
exploitation rate (E = 0.84) reflects a possible overfishing
situation. The situation is alarming and the authorities
must act immediately in order to preserve the species in
the central coast of Algeria.
Acknowledgments
The authors are deeply indebted to all those who
helped in collection of fish samples.
References
Bouain, A. 1981. Serranus (Teleostei: Serranidae) of the southern
coasts of Tunisia; size at first maturity, reproduction period.
Cybium, 5(4): 65-75 (In French).
Bouain, A. 1983. Linear growth of Serranus on the southern
coast of Tunisia. Report of the International Commission
for the Scientific Exploration of the Mediterranean Sea,
28(5): 87-91 (In French).
Carpenter, K. E. and De Angelis, N. 2016. The living marine
resources of the Eastern Central Atlantic, vol. 4: Bony
fishes, part 2 (Perciformes to Ttradontiformes) and sea
turtles. FAO species identification guide for fishery
purposes, Food and Agriculture Organisation of the United
Nations, Rome, Italy, p. 2343-3124.
Dieuzeide, R., Novella, M. and Rolland, J. 1959. Catalog of fish
from the Algerian coasts, vol. II: Osteopterygiens. Bulletin
of the work of the Castiglione aquaculture and fishing
station, Algers, 299 pp. (In French).
Djabali, F., Mehailia, A., Koudil, M. and Brahmi, B. 1993.
Empirical equations for the estimation of natural mortality
in Mediterranean teleosts. NAGA, ICLARM Q., 16(1): 35-37.
Fisher, W., Bauchot, M. L. and Schneider, M. 1987. FAO
Species identification sheets for fishing needs (Revision 1),
Mediterranean and Black Sea, Fishing zone 37, vol. II:
Vertebrates. Food and Agriculture Organisation of the
United Nations, Rome, Italy, p. 760-1530 (In French).
Froese, R. 2006. Cube law, condition factor and weight-length
relationships: History, meta-analysis and recommendations.
J. Appl. Ichthyol., 22(4): 241-253. Doi:10.1111/j.1439-04
26.2006.00805.x.
Growth and mortality of Serranus cabrilla
2016); 2.29 (Tserpes and Tsimenides, 2001) and 2.10
(Torcu-Koc et al., 2004), 2.23 (Ilhan et al., 2010) in the
Western Mediterranean. This would indicate that S. cabrilla
of the central coast of Algeria grows faster than in the other
regions. As for variable minimum and maximum lengths
in the different areas, fluctuations in growth parameters
(L ∞ , K) can be explained by variations in the environmental
and the ecological factors (temperature, mortality and
food availability) from one area to another (Korcu-Koc
et al., 2004).
We must consider that different techniques have
been used in the regions studied (Bouain, 1983; Tserpes
and Tsimenides, 2001; Torcu-Koc et al., 2004; Ilhan
et al., 2010; Gordo et al., 2016). The methodology used
in each region also explains the differences between the
obtained results.
The allometry coefficient “b” was 2.963. Similar
results have been reported by Ilhan et al. (2010) and
Moutopoulos and Stergion (2002) in Aegean Sea, by
Gordo et al. (2016) in Portugal and by Rachedi and Dahel
(2019) in the Gulf of Annaba. Unlike those obtained by
Torcu-Koc et al. (2004) in Edremit Bay and by Goncalves
et al. (1997) in Portugal, which showed negative
allometric growth. Ozvarol (2014) in the Gulf of Antalya
presented positive allometric growth for the species
(Table 2). In general, the b parameter is subject to changes
due to sample size, environmental factors and seasonality
(Froese, 2006).
Growth and mortality estimations are important for
understanding population dynamics (Ralston and Williams,
1988). We estimated the natural (M) and total mortality
(Z) at 0.43 and 2.63 yr
-1
, respectively. The estimated M
value was close to the value obtained in other regions.
Gordo et al. (2016) reported a total mortality rate between
0.44 and 0.48 yr
-1
in the eastern Atlantic (Portugal),
Tserpes and Tsimenides (2001) reported 0.35 yr
-1
at the Cretan Shelf (Greece) and Torcu-Koc et al. (2004)
obtained 0.32 yr
-1
in Edremit Bay (Turkey). On the other
hand, the value of natural mortality (M = 0.81 yr
-1
)
obtained by Rachedi and Dahel (2019) in the Gulf of
Annaba was higher than the value obtained in this study.
In fact, according to Sparre and Venema (1996) values of
natural mortality coefficients for the same species may
be different in distinct areas, depending on the density of
predators and competitors whose abundance is otherwise
influenced by fishing activities. Even small changes in
growth parameters could seriously affect the calculated
mortality (Tserpes and Tsimenides, 2001).
The resulting exploitation rate, E = 0.84, is higher
than the optimal value (0.5) mentioned by Gulland (1971).
Hence, the comber stock of this species is overexploited
in the study region. This situation could have an impact
on recruitment if individuals are caught during the
reproduction period (Sossoukpe et al., 2013).
Our study was carried out in order to estimate the
growth and the exploitation parameters of the comber
S. cabrilla from Bou Ismail Bay, Algeria. The determined
parameters are necessary for the stock assessment and
management of this species in the central coast of Algeria.
The inshore fishery for the comber S. cabrilla in Bou
Ismail Bay targets mainly individuals between 14 and
16 cm in total length (59.95%), while larger (24-26 cm)
and smaller individuals (9-11 cm) are caught in smaller
proportions (1.66%). The length-weight relationship of
this species shows that growth in length and weight is
isometric (a = 0.0119, b = 2.96, r² = 0.93). The calculated
exploitation rate (E = 0.84) reflects a possible overfishing
situation. The situation is alarming and the authorities
must act immediately in order to preserve the species in
the central coast of Algeria.
Acknowledgments
The authors are deeply indebted to all those who
helped in collection of fish samples.
References
Bouain, A. 1981. Serranus (Teleostei: Serranidae) of the southern
coasts of Tunisia; size at first maturity, reproduction period.
Cybium, 5(4): 65-75 (In French).
Bouain, A. 1983. Linear growth of Serranus on the southern
coast of Tunisia. Report of the International Commission
for the Scientific Exploration of the Mediterranean Sea,
28(5): 87-91 (In French).
Carpenter, K. E. and De Angelis, N. 2016. The living marine
resources of the Eastern Central Atlantic, vol. 4: Bony
fishes, part 2 (Perciformes to Ttradontiformes) and sea
turtles. FAO species identification guide for fishery
purposes, Food and Agriculture Organisation of the United
Nations, Rome, Italy, p. 2343-3124.
Dieuzeide, R., Novella, M. and Rolland, J. 1959. Catalog of fish
from the Algerian coasts, vol. II: Osteopterygiens. Bulletin
of the work of the Castiglione aquaculture and fishing
station, Algers, 299 pp. (In French).
Djabali, F., Mehailia, A., Koudil, M. and Brahmi, B. 1993.
Empirical equations for the estimation of natural mortality
in Mediterranean teleosts. NAGA, ICLARM Q., 16(1): 35-37.
Fisher, W., Bauchot, M. L. and Schneider, M. 1987. FAO
Species identification sheets for fishing needs (Revision 1),
Mediterranean and Black Sea, Fishing zone 37, vol. II:
Vertebrates. Food and Agriculture Organisation of the
United Nations, Rome, Italy, p. 760-1530 (In French).
Froese, R. 2006. Cube law, condition factor and weight-length
relationships: History, meta-analysis and recommendations.
J. Appl. Ichthyol., 22(4): 241-253. Doi:10.1111/j.1439-04
26.2006.00805.x.
Growth and mortality of Serranus cabrilla