Distribution and Growth of Grey Triggerfish, Balistes capriscus (Family: Balistidae), in Western Gulf of Guinea

The grey triggerfish, Balistes capriscus, resource had declined for nearly two decades in West African waters; its distribution and growth remain to be reported after late 1980s. In order to fill this gap, specimens were collected during small pelagic fish stock assessment surveys in 2005 in coastal waters of Benin, Togo, Ghana and La Côte d’Ivoire (Western Gulf of Guinea) from 17 out of 165 swept-area hauls in depths range of 23–60 m. The modal size classes were 27.0–31.9 cm and 32.0–36.9 cm. The age classes were determined by interpreting growth rings on sections of first dorsal spines. Estimates of theoretical growth in length were obtained by fitting the observed length-at-age data to the standard form of von  Bertalanffy growth equation. The estimated L∞ for B. capriscus was 45.1 ± 1.4 cm and the growth rate, K, was 0.21 yr-1. The phi prime (Ö’) growth performance obtained was 2.63, which is comparable to that obtained in the 1980s on the same fish species in waters of Senegal, La Côte d’Ivoire and Ghana. The results suggest that the growth and distribution of grey triggerfish in the Western Gulf of Guinea had not changed, in spite of the apparent disappearance of the fish species in many areas of the West African coastal waters for nearly two decades

Variability of Otolith Morphology in Major Fish Species in Coastal Waters of Cape Coast-Elmina, Ghana

The fish sagittae otoliths have unique structures for various fish species. These otoliths are very important hard parts in fish for growth and age studies. In this study, sagittae otoliths of major marine finfishes were analysed and compared using descriptive morphological characters. Information obtained was a first step that would lead to future age and growth studies on these fishes for stock assessment in fisheries management. The study was conducted in 2017, and 38 fish species belonging to 21 families were encountered in the beach seine landings (Cape Coast) and artisanal canoe and semi-industrial landings (Elmina), all in the Central Region of Ghana. The fish species and their respective sagittae otoliths were extracted using standard methods and all were digitally photographed. The observed differences among the otoliths were in their overall shape, margins and anterior region that were described to be oblong, obovate, discoid, oval, rhomboidal, anvil-shaped, ovate, circular, triangular, elliptic, spindle-shaped, tear-drop and rectangular. The margins were observed to be irregular, crenate and sinuate for various otoliths. Ranges of fish total lengths and sagittae otolith lengths were presented for various fish species encountered during the study. The largest otolith lengths were recorded in Pseudotolithus senegalensis (82 – 230 mm TL; 4.7 – 8.0 mm OL) and the smallest otolith lengths were observed in Sardinella aurita (76 – 209 mm TL, 1.4 – 3.5 mm OL). The results of these sagittae otoliths descriptions in this study would be a useful information towards ageing of finfishes which is lacking in Ghanaian waters

Length-Weight Relationships and Food Preference of Two Coastal Marine Fishes, Galeoides decadactylus (Polynemidae) and Sphyraena sphyraena (Sphyraenidae) off Cape Coast, Ghana

The food and feeding habits of most commercially important marine fish species in Ghana had not been studied. The aim of the paper was to study the diet spectrum of two coastal fishes of Ghana; Galeoides decadactylus (Polynemidae) Bloch, 1795 and Sphyraena sphyraena (Sphyraenidae) Linnaeus, 1758, both of tropical fish species. Fish samples were obtained in 2011 from sandy beaches near Cape Coast township in the Central Region of Ghana, noted for beach seining. Length-weight measurements were taken from well-preserved fish specimens from which stomachs were extracted for the analysis of the food contents, using frequency of occurrence, numerical and gravimetric methods, as well as index of relative importance. The length-frequency analysis showed a size distribution with a modal size of 11.0–13.9 cm for both species. The length-weight relationships for both fish species showed strong correlation between the weight and length with correlation coefficient (r2) and exponent b for Galeoides decadactylus as 0.9869 and 2.9893, and that for Sphyraena sphyraena as 0.9861 and 2.9094, respectively. Juvenile shrimp and fish fry formed the bulk of the food items in the stomachs of the two fish species. Juvenile shrimps occurred in 77.18% of the stomachs observed for G. decadactylus and accounted for 80.20% of the total number of the food items whilst comprising 63.14% of the weight of food consumed. That of S. sphyraena was, respectively, 66.7% by frequency, 87.0% by numbers and 96.3% by weight. Juvenile shrimp had the highest IRI in the diet of G. decadactylus whereas in S. sphyraena fish fry recorded the highest IRI. Literature evidence showed that the diet spectrum and aspects of growth of the two fish species reported elsewhere in the tropics were comparable to that off the coast of Cape Coast despite the differences in geographical location. The findings in this study will contribute to the knowledge gap on the diet of most commercially important fish species in Ghanaian waters

Growth, Mortality, Sexual Maturity and Exploitation Level of the Golden African Snapper (Lutjanus fulgens, Lutjanidae) in Ghanaian Waters

The golden African snapper, Lutjanus fulgens, is one of the most commercially important demersal species exploited by commercial fishers along the coast of Ghana. Growth and mortality as well as aspects of reproduction of L. fulgens were studied to contribute to the paucity of biological information on the species in Ghanaian waters. Samples were collected along the coast of Ghana from September 2018 to August 2019. Total lengths of L. fulgens sampled ranged between 16.2 and 45.6 cm. Length-weight relationship of the species showed isometric growth pattern. The asymptotic length (L∞), growth coefficient (K) and age at zero length (to) for L. fulgens were estimated as 51.09 cm, 0.47 yr-1 and -0.301yr respectively. Total (Z), fishing (F) and natural (M) mortality rates of L. fulgens were estimated at 2.69 yr-1, 1.91 yr-1 and 0.78 yr-1 respectively. The length-at-first capture (Lc) = 31.51 cm, was slightly lower than the length-at-first maturity (Lm) = 33.7 cm for females. The exploitation ratio (E = 0.71) of the stocks in Ghanaian waters was above the optimal exploitation levels. Peak spawning period was observed from July to September. Mean fecundity was estimated to be 77,833 ± 13,012 eggs (mean ± SE). There was no significant difference observed in the sex ratio between males and females. The findings suggest the stocks are under high fishing pressure and so it is recommended that to avoid exploiting the spawning biomass, closed season could be observed during the spawning periods

Species Diversity and Relative Abundance of Fisheries Resources Found in Beach Seine along the Central Coast of Ghana

The diversity and relative species abundance of fisheries resources were studied from Winneba to Cape Coast on the central coast of Ghana during December 2007 to May 2009. Samples of organisms were collected at random from beach seine landings during the study period. The fishes were counted and identified to the family and species levels. Ecological indices such as Shannon-Wiener diversity index, equitability and Sørenson’s similarity index were used to analyse the data. Specimens from Winneba, Saltpond and Cape Coast comprise 56 species belonging to 30 families. Carangidae, Haemulidae, Clupeidae and Sciaenidae were some of the families, where key species occurred during the study. The relative abundance of key organisms in the beach seine landings include Chloroscombrus chrysurus (26.0%) in 2007, Brachydeuterus auritus (22.8%) in 2008, Ilisha africana (14.7%) in 2008, Sardinella aurita (13.1%) in 2009 and Selene dorsalis (11.2%) in 2007. The organisms that were in low relative abundance were Acanthurus monroviae, Penaeus notialis, Galeoides decadactylus and Trichiurus lepturus. Shannon-Wiener diversity index, estimated in the study, ranged from 2.54 to 2.83. Species equitability range was 0.67–0.77, and the Sørenson’s similarity estimated ranged was 0.66–0.69. The estimations of fish species diversity and equitability were higher (H’ = 2.83; J’ = 0.77) during the 2009 study in the central coast of Ghana. The similarity indicators in the various paired periods during the study showed considerable similarity in the organisms that were exploited by the beach seine in the area. The study explains the linkage between the diversity and relative species abundance of the coastal fisheries resources and offshore marine resources in Ghana, and the need to regulate beach seine operations in order not to over exploit the juvenile stocks

Rapid Assessment of Anthropogenic Impacts of Exposed Sandy Beaches in Ghana using Ghost Crabs (Ocypode Spp.) as Ecological Indicators

We applied a rapid assessment methodology to estimate the degree of human impact of exposed sandy beaches in Ghana using ghost crabs as ecological indicators. The use of size ranges of ghost crab burrows and their population density as ecological indicators to assess extent of anthropogenic impacts on beaches was explored in this study. For each site, three transects were laid perpendicular to the shoreline over a 100 meter distance at 50 m intervals, i.e., at reference points 0, 50 and 100 meter points. Sampling locations were randomly selected along the three transects using a 1 m x 1 m quadrat. Measurements were done twice weekly for a period of four weeks. The results showed that even though the moderately disturbed beach had higher burrow density than the disturbed beach on the average, the difference is not statistically significant (T-test; p > 0.01). However, mean burrow diameter at the moderately disturbed site was statistically found to be significantly larger than for the disturbed site (T-test; p < 0.01). We conclude that burrow sizes is a good estimator for verification of human impacts of exposed sandy beaches. It confirms that burrow density even though an important factor, may not necessarily be a significant estimator of the impacts of human activity on beaches. On this basis, it appears that the estimations of the diameter of burrows of crabs of the Ocypode genera provides a rapid tool for impact verification of sandy beaches and for use in environmental quality monitoring of beach programs in coastal areas

Length-Weight Relationship and Distribution of Tympanotonus Fuscata (Mollusca: Potamididae) in Brenu Lagoon, Ghana

A total of 1894 specimens of Tympanotonus fuscata were obtained by random sampling with Ekman grab from Brenu Lagoon to determine the size distribution of the organism as a result of perceived human predation on the resource in the area. Samples of the edible snail were col-lected monthly from November 2003 to October 2004, and the physico-chemical parameters de-termined for the entire study period. Variations were observed in the quarterly mean density (numbers/cm3) of the snails in all the four sampling stations A to D with values ranging from 18.67±4.81 to 99.00±17.80 at station A, 21.67±7.06 to 29.33±4.41 at station B, 21.70±10.50 to 71.70±12.30 at station C and 9.67±7.22 to 41.30±5.70/ cm3 at station D. There were patchy distri-butions of the snail in the lagoon at replicate stations which might be due to the variation of physical conditions in the water. The height-weight relationship of the snail indicates negative allometric growth with high individual variability and the body weight was most closely related to the shell height (R2 = 0.89). The snails in Brenu Lagoon were not growing to the large size this was observed in size frequency distribution. The modal size class was 1.5 – 1.9 cm. The domination of smaller snail size could be due to human predation pressure on the larger snails and or the effect of physical and chemical factors that prevail in Brenu Lagoon

Preliminary studies on copepod infestation of the garfish (,i>Ablennes hians) landed at Elmina harbour, Ghana

A study was conducted to investigate the degree and effect of copepod infestation of the buccal cavity of the gar fish landed at the Elmina harbour in Central Region of Ghana, on some body parameters and sexratio of the fish. The results indicate that the degree of infestation was significantly high (64.19%) compared to non-infestation (35.81%). The highest infestation (21.30%) occurred in animals with standard length classinterval of 75.0-79.9 cm and the least (3.40%) was in 80.0–84.9 cm. The highest infestation was recorded in the breadth class interval of 60.0-6.9 cm. The least (5.70%) was in 5.0-5.9 cm. The mean standard length of the infested animal was 74.45 ± 6.50 cm, while that of the non-infested was slightly higher (77.45 ± 6.36 cm). Mean body depth of the infested was slightly lower (6.94 ± 0.86 cm) than that of the non-infested (7.08 ± 0.94 cm). Mean condition indices of infested and non-infested garfishes were similar (about 1.42 x 10-1) for each group. Sex ratios of infested (1:1.02) and non-infested (1:1.36) did not differ significantly. Similarly, the standard length-gill length and gill volume of infested and non-infested garfishes were close to each other, but slightly more positive for the non-infested animals. Finally, the results of biochemical composition indicate that the various components did not differ significantly between infested and non-infested. Protein content was high(20.30%), but fat content was rather low (8.50%) for both infested and non-infested garfishes. It is concluded that infestation had no significantly negative effect on the garfish

Sensitive and specific detection of ligands using engineered riboswitches

Riboswitches are RNA elements found in non-coding regions of messenger RNAs that regulate gene expression through a ligand-triggered conformational change. Riboswitches typically bind tightly and specifically to their ligands, so they have the potential to serve as highly effective sensors in vitro. In B. subtilis and other gram-positive bacteria, purine nucleotide synthesis is regulated by riboswitches that bind to guanine. We modified the xpt-pbuX guanine riboswitch for use in a fluorescence quenching assay that allowed us to specifically detect and quantify guanine in vitro. Using this assay, we reproducibly detected as little as 5 nM guanine. We then produced sensors for 2′-deoxyguanosine and cyclic diguanylate (c-diGMP) by appending the P1 stem of the guanine riboswitch to the ligand-binding domains of a 2′-deoxyguanosine riboswitch and a c-diGMP riboswitch. These hybrid sensors could detect 15 nM 2′-deoxyguanosine and 3 nM c-diGMP, respectively. Each sensor retained the ligand specificity of its corresponding natural riboswitch. In order to extend the utility of our approach, we developed a strategy for the in vitro selection of sensors with novel ligand specificity. Here we report a proof-of-principle experiment that demonstrated the feasibility of our selection strategy.United States Department of Defense-Defense Threat Reduction Agency (MIPR HDTRA1620511); Office of Naval Research; Chemistry Department of the U.S. Naval Academ