Open Access Original Research Article

Sexual Dimorphism in Erpetoicthys calabaricus from a Mangrove Creek, Nigeria

I. E. Asuquo, M. A. Essien-Ibok

Asian Journal of Fisheries and Aquatic Research, Page 1-9
DOI: 10.9734/ajfar/2018/v2i328689

Sexual dimorphism of E. calabaricus is presented based on the examination of external morphology of the fish. Females had very pointed anal fins which joined the caudal fin smoothly with fewer than 10 spikes. Males had broader anal fin clearly separated from the caudal fin with between 9 and 12 spikes on the fin. Colour dimorphism in males tended towards an olive green, whereas the females had a light yellow-brown colour. Paired t-test showed that active females were slightly heavier than similarly-sized males. Length frequency distribution showed the largest fish was 39.9 cm TL female, while the smallest fish (TLmin) was 21 cm TL male. Sex ratio was in favour of males giving a male: female ratio of 1: 0.79 which was different from the expected 1: 1 ratio (χ2 = 9.110, df = 1, p < 0.05). The smallest female and male were 21.7 cm and 21 cm TL, thus delineating minimum sizes in the population. Largest female and male fishes measured 39.9 cm and 39.7 cm TL. Median sizes were 28.0 cm (females) and 29.0 cm (males).

Open Access Original Research Article

Preliminary Trials on Hatchery and Larval Development of the Sea Cucumber, Holothuria scabra (Jaeger 1883), in the Sultanate of Oman

Khalfan M. Al-Rashdi, Michel R. Claereboudt, Igor Eeckhaut

Asian Journal of Fisheries and Aquatic Research, Page 1-9
DOI: 10.9734/ajfar/2018/v2i330009

Although sea cucumber Holothuria scabra has always been part of the traditional exploitation of the benthos of Mahout Bay in the Arabian Sea, the foreign demand for the product and its high price have put increased pressure on the resource leading rapidly to overfishing. Aquaculture of this species has developed as a response to the overfishing problem but has not been yet studied in Oman. As a first step to evaluate its potential for aquaculture in Oman it was thus necessary to conduct hatchery trials. Four hatchery trials were conducted to evaluate the quality of the local broodstock, the response and efficiency of in-vitro maturation and fertilization and the success of larval development and rearing. Collected animals of 200-600 g were transported by road for 5 hours with zero evisceration to the Hatchery station. In-vitro maturation and fertilization success of more than 90% were achieved using the maturation inducing fractions (MIF) method leading to the development of mature eggs and normal embryos larvae. Auricularia larval stages were completed within 15 days and fed normally on microalgae Phaeodactylum tricornutum, Chaetoceros sp. and Nanochloropsis sp. Average settlement rate and size for pentactula juveniles were closely to 9% and 0.5 mm, respectively, nearly one month post-fertilization (PF). However, a high mortality of 70% was observed during early larval development caused by ciliated protozoans and copepods attack. The culture of H. scabra population in Oman is thus promising but further research is needed to ensure higher survival rates, particularly in the early larval stages where adequate water filtration and sterilization is essential.

Open Access Original Research Article

The Effect of Partial Replacement of Fishmeal with Citrullus lanatus and Moringa oleifera Seed Meals on Growth Performance of Clarias gariepinus (Burchell, 1822) Juveniles

F. E. Avwemoya, F. Eze

Asian Journal of Fisheries and Aquatic Research, Page 1-8
DOI: 10.9734/ajfar/2018/v2i330010

Four experimental diets were formulated to contain Citrullus lanatus, Moringa oleifera seed meal, Citrullus lanatus and Moringa oleifera seed meals as partial replacement for fishmeal (Treatment 2, 3 and 4 respectively) and Treatment 1 as control, which included fishmeal and soy bean meal as the protein sources. The fed were to one hundred and twenty (120) African catfish (Clarias gariepinus) of mean weight of 25±5.0 g and mean length of 14±2.0 cm in replicates for 10 weeks growth period. The results obtained showed that fish fed treatment 3 had highest mean weigh gain. More so, treatment 1 had the highest percentage weight gain and specific growth rate. Treatment 4 had the highest food conversion ratio and treatment 1 had the highest length increase. The result of the economic analysis of the four treatments showed the treatment 4 and 3 are the cheapest while treatment 1 is the most expensive. All the treatment diets showed that growth due to the different protein sources were not significant (p>0.05). The result of this study therefore revealed that partial replacement of fishmeal with Moringa oleifera seed meal can be used in the diet of Clarias gariepinus juveniles.

Open Access Original Research Article

Implications of Seagrass Ecosystem Degradation on Marine Resources and People’s Livelihood: A Case Study from Komave Village, Fiji

Lionel Joseph, Priyatma Singh, Ajay Ashneel Singh, Kushaal Raj, Anish Maharaj

Asian Journal of Fisheries and Aquatic Research, Page 1-13
DOI: 10.9734/ajfar/2018/v2i330011

Tropical coastal zones have rich marine ecosystems; however, they have been enduring severe environmental hazards, particularly from anthropogenic activity and the effects of climate change. Seagrass ecosystem is one of the most productive yet undervalued marine ecosystems. The residents of Komave village, located on the mainland of Fiji have witnessed marked losses in seagrass cover over the last decade. Several of the village men in Komave are unemployed and rely on the coastal resources through fishing, livestock and agricultural farming for their socioeconomic livelihood. This research explores the impact of loss of seagrass cover on the villagers’ livelihood. This paper highlights the observations and experiences of the Komave villagers, in light of the interviews and discussions carried out at the community. A random sampling method was also used over a period of two years (March, 2015 – April, 2017) to monitor the seagrass habitat. The possible anthropogenic and natural factors contributing to the loss of Seagrass were gotten from the interviews and sampling physical environment. The nitrate content analysed from the random samples, reported values from 190 mg/L to a maximum value of 362.8 mg/L. It was also revealed that the areas where nitrate concentrations were greater than 300 mg/L, there was 0% sea grass cover in total, which confirms that if high levels of nitrates are present, sea grass cover is highly impacted. This paper concludes by providing recommendations for managing seagrass to enhance fisheries productivity in this tropical coastal community.

Open Access Original Research Article

Comparative Assessment of Single and Joint Toxicity of Bulk and Nano Scale Heavy Metals (Al2O3, CuO and SiO2) Using Haematological Parameters as Biomarker in Juvenile African Catfish (Clarias gariepinus)

Tam-Miete D. Briggs, Nnamdi H. Amaeze, Henry E. Obanya

Asian Journal of Fisheries and Aquatic Research, Page 1-17
DOI: 10.9734/ajfar/2018/v2i330013

Global technological advancement has resulted in the gradual replacement of traditional bulk size compounds with nano-sized ones with diverse useful characteristics. This study is focused on the toxicological assessment of three nano-metallic oxides (SiO2, Al2O3 and CuO) in comparison with their equivalent bulk sizes using African Catfish (Clarias gariepinus). The study involved sub-lethal exposures to binary mixtures of selected ratios (1:1; 2:1 and 1:2) of the respective metallic bulk and nano oxides as well as their triple mixture (1:1:1) for 28 days. The catfishes after 28 days were subsequently subjected to haematological tests (Haemoglobin, Packed Cell Volume, Red blood cells, Platelets, Neutrophils, Lymphocytes, Mean cellular volume, Mean Cell haemoglobin, and Mean Cell haemoglobin Concentration). The results of the haematological assessment indicated that most of the nano-sized oxides showed no significant difference (P>0.05) compared to control whereas the bulk sizes either showed no difference or decrease in the count compared to control. In most of the binary mixtures, catfishes exposed to bulk sizes had lower levels of the haematological parameters but there was no overall trend. The introduction of nanoscale metallic oxides into production activities should be with caution since they may have a similar mode of toxicity to the existing bulk sizes.