Effect of seismic operations on cetaceans sightings off-shore Akwa Ibom State, south-south, Nigeria

The possible behavioral and physical problems involving cetaceans and marine seismic surveys have attracted the interest and concern of several authors. However, studies on cetaceans frequenting Nigerian waters have not been detailed in literature. This research work is appropriately driven by these requirements. Opportunistic data was collected on board six different marine vessels belonging to ExxonMobil. Data collected were analyzed using descriptive statistics, t-test and ANOVA at p=0.05. A total of 8,327 hours 36 minutes observation effort was accomplished during twenty-six months, representing almost 800 km2 of coverage. Two hundred and eighty-three (283) sightings were recorded comprising of 189 (66.78%) sightings of whales and 94 (33.22%) sightings of dolphins. Four species of cetaceans were identified, bottlenose dolphins (Tursiops truncatus) were the most abundant followed by pantropical spotted dolphins (Stenella attenuata). These two species occurred throughout the sampling months, while the predominant whales specie were the humpback whale (Megaptera novaeangliae) and killer whales (Orcinus orca) which seem to be present in just a part of the year. Whales were sighted more when the guns were active. Conversely, less of the dolphins were sighted while the guns were active. There were significant differences (P=0.05) regarding the air-gun operational state between the number of whales and dolphins sightings. The result suggests that swimming behavior was dependent of air-gun operational state.Keywords: Cetaceans, seismic survey, Sightings, Akwa Ibom state, south-south Nigeria

Length- weight relationships, condition factor (K) and relative condition factor (Kn) of Sparids, Dentex congoensis (Maul, 1954) and Dentex angolensis (Maul and Poll, 1953), in Nigerian coastal water

Length-weight relationship and condition factors were estimated for Dentex congoensis and Dentex angolensis of the family sparidae trawled from Nigeria Coastal water in 2009. A total number of 534 specimens ranging from 7.2 – 3.0 cm in total length and 5.4 – 489.8 g in weight were analyzed. The lengthweight relationship is shown by the following equations: LogW –1.610 + 2.791logL (Dentex congoensis) and LogW = -1.558 + 2.776logL (D angolensis). The two species studied exhibited negative allometric growth (b < 3) with the mean b = 2.78 at p < 0.001. The correlation coefficient (R) values were 0.91 (Dentex congoensis) and 0.98 (D angolensis). The condition factor (K) and relative condition factor (Kn) were determined for each species separately. The condition factor (K) obtained for Dentex congoensis and Dentex angolensis were between 0.86 – 8.04 with mean value of 2.48 ± 0.58 and between 2.06 – 6.13 with mean value of 2.79 ± 0.42 respectively. The relative condition factor (Kn) values were 1.28 ±1.09 (Dentex congoensis) and 1.66 ± 2.44 (Dentex anoglensis). The maximum ‘Kn’ values were recorded during the length at first maturity and there was a general decreased in relative condition factor (Kn) with increase length for the two species

Occurrence of finfish communities in trawl hauls of Atlantic Ocean in Badagry coast, Nigeria

Thirteen trawl hauls were conducted at depths ranging from 10 m – 100 m. Fifty six finfish families were observed, comprising ninety seven species from eighty two genera. Ten commercially important finfish families were identified out of which the Haemulidae had the highest number of occurrence and distribution with catch per unit area (CPUA) of 36.17 Kg/Km2. The Carangidae with CPUA of 22.09 Kg/Km2 was the lowest in abundance and distribution of the important finfish families. The total biomass estimate of finfishfrom the entire survey area under investigation was 440 tons (t). The middle stratum, S2 (30 m – 70 m) had the highest biomass followed by the land adjoining stratum, S1 (10 m -30 m) and the least stratum biomass wasobtained from the farthest stratum, S3 (70 m – 100 m). Fishing is optimized in the middle stratum, S2