Food and feeding habits of Lagocephalus sceleratus (Gmelin, 1789) in some areas of the eastern coast of Libya (Published)
The puffer fish Lagocephalus sceleratus (Gmelin, 1789), family Tetraodontidae, is a Lessepsian species which has invaded the Eastern basin of the Mediterranean Sea. The present work is the first study that gives an account of length-weight relationship, condition factors and feeding habits of L. sceleratus in the eastern coast of Libya.L. sceleratus were randomly sampled monthly during January to December 2015 from the artisanal catch of Ain El-Ghazala lagoon (a total of 146 specimens) and Derna coast (22 specimens) on eastern Libya. Ain El- Ghazala fish had total length ranging from 19.5 to 73.4 cm corresponding to total weight of 149.3 to 4000.5 g. Total length of Derna L. sceleratus ranged from 49.5 to 73.4 cm corresponding to total weights of 1657.2 to 4011.8 gm. The length (L) weight (W) relationship W = 0.01881 *L2.8774, n = 146, R2 = 0. 7135 reflects a near isometric growth for Ain El- Ghazala fish (b = 2.8774). Fulton and Clark condition factors (KF and KC) of Ain El- Ghazala L. sceleratus were high in spring (1.34 and1.23 consecutively) and summer (1.43 and 1.21) and low in winter (1.21 and 1.13) and autumn (1.25 and 1.16).Mollusks (72.5%), supplemented by crustaceans (17.4%) and fishes (10.2%), composed the diet of Ain El-Ghazala L. sceleratus. Mollusks dominated the diet in all seasons, followed by crustaceans, then fishes. Feeding intensity was high during spring (83.5%) and autumn (72.6%) and low in winter (41.6%) and summer (28.3%). Uptake of mollusks decreased as L. sceleratus size increased, while that of crustaceans and fishes increased. Derna L. sceleratus of all sizes (49.5-73.4 cm) fed only on fishes (100%).
Preliminary Investigation of Length-Weight Relationship and Condition Factor of Periwinkle (Tympanotonus Fuscatus, Linnaeus 1758) From Okrika Estuary, Niger-Delta Area of Nigeria (Published)
Assessment of length-weight relationship and condition factor of a commercially important mollusc species, Periwinkle, Tympanotonus fuscatus, from Okrika estuary was conducted from October, 2015 to February, 2016. A total of 120 samples of the species were hand-picked from the mangrove ecosystem of Okrika. The results obtained showed that the gastropod species had negative allometric growth patterns with a growth exponent, b value of 2.18. This value was confirmed as negative allometric, because it was significantly different (p<0.05) from 3 when a t-test was carried out. The mean condition factor, K of the species was 18.9, which indicated that they were in good condition during the sampling period. This study recommends that further research needs to be conducted because the sampling duration was one-third of a year (4 months). Also efforts should be taken to reduce the pollution load in order to safe-guard this valuable resource for the local population.
Length-Weight Relationship, Condition Factor and Food and Feeding Habits of Seriola Dumerili (Risso, 1810, Carangidae) In Al-Hamama, Eastern Libya Mediterranean Sea (Published)
Stomachs of 235 pre-adult (PA) and 111 adult (A) Seriola dumerili obtained monthly from Al-Hamama (eastern Libya Mediterranean Sea) artisanal catch during November 2012 to October 2013 were examined to study food and feeding habits of the fish. The length-weight relationships of “PA” and “A” were W = 0.0437L2.819, n = 235, R2 = 0.99 and W = 0.019L2.873, n = 111, R2 = 0.99, indicating isometric growth. Annual ranges of monthly values of Fulton (KF) and Clark (KC) condition factors were 2.35 to 3.1 and 1.71 to 2.52 for “PA” and 0.98 to 1.44 and 0.69 to 1.22 for “A” in order. Relationships of both factors with fish length and months and seasons of the year were established. “PA” KF and KC recorded highest values in autumn and spring, which coincided with the period of highest degree of stomach fullness. “A” KF and KC recorded highest values in spring and summer, which coincided with the period of stomach fullness in spring and the spawning season in summer. Food items of “PA” according to order of importance were crustaceans, mollusks, polychaetes, sea grass and bony fish. Those of “A” were bony fish, mollusks, crustaceans, sea grass and polychaetes. Dependence of “PA” on crustaceans, mollusks and bony fish increased with increasing fish length while that on the other items decreased. Dependence of “A” on bony fish and mollusks increased with increasing fish length while dependence on the other items decreased. “PA” prefers feeding on crustaceans and sea grass in summer, on mollusks and bony fish in spring and on polychaetes in autumn. “A” prefers bony fish in autumn and summer, mollusks and polychaetes in spring, crustaceans in winter and sea grass in summer. Monthly and seasonal feeding intensity were established. The feeding intensity was high during autumn and spring for “PA” and moderate to high during all seasons for “A”.
Length-Weight Relationship and Growth of the Striped Seabream Lithognathus Mormyrus (Linnaeus, 1758) From Al Haneah Fish Landing Site, Mediterranean Sea, Eastern Libya (Published)
Length-weight relationship and growth characteristics of the striped Seabream Lithognathus mormyrus (Linnaeus, 1758) was established using 164 fish collected from Al-Haneah (eastern Libya, Mediterranean Sea) artisanal catch during March to October 2015. The power relationship between total weight (W in gm) and total length (L in cm) for L. mormyrus was highly isometric: W = 0.0132L^3.0008 (R2 = 0.8291). The length based von Bertalanffy equation of the order: Lt = L∞ (1 – exp (-K (t –t0 ))) was Lt = 30.465 (1 – exp (-0.159 (t + 2.5435))). The weight based equation was Wt = 374.2523 (1 – exp (- 0.159 (t + 2.5435))) 3.0008. The growth index was low: ɸ = 2.169.