Journal of Fisheries

Microbiological assessment of Nile tilapia Oreochromis niloticus collected from different super shops and local market in Dhaka, Bangladesh

2020-06-28T13:50:20+00:00

The present study was conducted to detect the bacterial contamination of Nile tilapia Oreochromis niloticus collected from super shops and local market of Bangladesh. The sample specimens were collected from three super shops in Dhaka city viz. Agora, Shwapno and Prince Bazar and one local market (Savar Bazar). Samples were analysed to determine some pathogenic bacterial genera through the isolation and enumeration from different organs. The isolates were identified as Escherichia coli, Salmonella spp., Shigella spp. and Vibrio spp. by conventional culture method, biochemical tests and PCR assay. Total Viable Bacterial Counts (TVBC) were also determined. Fishes were found to be contaminated within a range between 6×10⁴ to 1.6×10⁶ cfu g^–1. The load of E. coli and Shigella spp. were higher than that of Salmonella spp. and Vibrio spp. in all the studied samples. The study concludes that more precautions are required for personnel hygiene during fish processing and handling in order to prevent assemblage of pathogenic bacteria in super shops as well as local fish markets of Bangladesh.

Population dynamics of bearded croaker Johnius dussumieri (Cuvier, 1830) from Pakistani waters

2020-06-07T20:55:34+00:00

In this study the length frequency data of 2510 bearded croaker Johnius dussumieri (Cuvier, 1830), collected from the coast of Pakistan during 2015, were analysed. Total length of the specimens (male and female combined) varied from 4 to 25 cm with dominant individuals ranged between 12 and 15 cm whereas the body weight varied between 3 and 155 g. The length frequency data were analysed for the estimation of population dynamics and the power coefficient b of length weight relationship was estimated as 2.83. Other measurements were as follows: asymptotic length, L_∞= 26.25 cm; growth coefficient, K = 1.00 year^–1; total mortality, Z = 2.43 year^–1; and natural mortality, M = 1.82 year^–1. The fishing mortality (F) and exploitation ratio (E) were 0.61 year^–1 and 0.251 respectively. The Biological Reference Points (BRPs) with Gulland method for this fishery (F_opt) was estimated 1.82 year^–1 which is higher than current fish mortality. Therefore the present study shows that the J. dussumieri fishery is safe in Pakistan.

Seasonal variation of cladocera in a perennial pond, Ambajogai (Maharashtra), India

2020-05-29T12:17:07+00:00

A systematic investigation on seasonal variations of cladocera in Udayan Sarovar, a perennial pond near Swami Ramanand Teerth Mahavidyalaya at Ambajogai (Maharashtra, India) was carried out for a period of one year from June 2018 to May 2019. A total of 9 species of cladocera were identified. The cladoceran diversity fluctuated seasonally and the maximum number of 240 organisms L^–1 was recorded during month of April and minimum number of 22 organisms L^–1 during the month of September.

Age, length-weight relationships and condition factors of endemic Antalya barb Capoeta antalyensis (Battalgil, 1943)

2020-05-27T11:54:47+00:00

The aim of this study was to determine the length-weight, length-length relationships (LWR and LLR) and condition factors of Antalya barb Capoeta antalyensis, an endemic species to Turkey. The specimens (N = 125) were caught using the gill nets in the Sorgun Dam (Aksu, Isparta). The age of the study specimens varied between one and six years. The total length and body weight of the specimens varied from 17.7 – 36.7 cm and 57.03 – 526.91 g respectively. A negative allometric growth (b = 2.7743) was recorded for the species whereas the LWR and total length (TL) – fork length (FL) equations were W = 0.0203 × TL^2.7743 (R² = 0.95) and TL = 0.402 + FL × 1.061 (R² = 0.99) respectively. The condition factor was determined for every specimen. In light of the results obtained in the study this species may be considered for aquaculture ensuring sustainable population in the wild. This study provides new information that can play an important role in the sustainable management this species.

Behavioural differences between breeding and nonbreeding pairs of protandry monogamous false clown anemonefish Amphiprion ocellaris

2020-05-25T10:00:03+00:00

Anemonefishes are some of the most popular marine ornamental fishes. Due to the adverse impacts of commercial fishing on the wild populations of anemonefishes, a more suitable and efficient captive breeding programme must be promoted. In the wild, anemonefishes are protandrous sex-changing fish, but when two immature individuals with ambisexual gonads are raised together in captivity, the two differentiate directly into a male and a female, to form a breeding pair. However, not all the formed pairs spawn, explaining the great care required in captive breeding. This behaviour appears to be counter-adaptative, as anemonefish social groups form randomly in the wild, and such phenomenon would disturb their breeding success. This study evaluated the behavioural and physiological differences between breeding and nonbreeding pairs of false clown anemonefish Amphiprion ocellaris under captive conditions. Behavioural observations revealed that nonbreeding females monopolized the shelter provided, whereas breeding females allowed breeding males to use the shelter and the pair frequently stayed together in the shelter. Both nonbreeding and breeding females possessed mature ovarian tissue and similar level of plasma estradiol concentrations, but nonbreeding males had a smaller amount of testicular tissue and lower plasma 11-ketotestosterone levels compared to breeding males.