Quality attributes,polycyclic aromatic hydrocarbon,and heavy metal profile of traditional drum-smoked Guinean barracuda fish from Lagos State,Nigeria

This study was carried out to assess the quality attributes, polycyclic aromatic hydrocarbon (PAH), and heavy metal profile of traditional drum-smoked Guinean barracuda fish from Lagos State, Nigeria. Fresh Guinean barracuda fish (60) samples were obtained from 20 different fish-processing centers. The fresh fish samples were smoked with traditional drum kiln. The fresh and smoked fish samples were analyzed for proximate composition, quality indices (peroxide value (PV), thiobarbituric acid (TBA), total nitrogen base-nitrogen (TVB-N), trimethylamine acid (TMA), and free fatty acid (FFA)), PAH, heavy metals, and microbiological (coliform, fungi, Listeria monocytogenes (LM), Salmonella paratyphi (SP), and Staphylococcus aureus (SA)) analyses. The results revealed that the mean moisture, protein, fat, crude fiber, ash, and carbohydrate contents of traditional drum-smoked fish samples were in the range 10.93–14.15%, 51.97–60.96%, 11.34–15.99%, 1.74–2.99%, 1.12–1.56%, and 7.70–17.99%, respectively. The values of PV, FFA, TBA, TVB-N, and TMA were in the range of 8.21–10.19 meq.peroxide/kg, 1.13–1.80%, 1.03–1.19 mgMol/kg, 17.29–19.36 mgN/kg, and 2.12–2.68 mgN/kg, respectively. The results of PAH compounds in the traditional drum-smoked fish samples showed that 10 of the 16 PAH compounds detected were above the 5.0 µg/kg B(α)P maximum permissible levels stipulated by EU Regulation 1881/2006. The concentrations of Hg, Pb, Cd, and Cr in the smoked fish samples ranged from 0.001 to 0.0027 µg/g, 0.0013 to 0.0028 µg/g, 0.0014 to 0.0028 µg/g, and 0.0621to 0.0796 µg/g, respectively. The results of microbiological analysis revealed the presence of LM and SA in the traditional drum-smoked fish samples. The study concluded that traditional drum-smoked fish may constitute higher risks (chemical and microbiological) and public health concerns to consumers.     

Rapid proliferation of the parasitic copepod,Salmincola californiensis (Dana), on kokanee salmon,Oncorhynchus nerka (Walbaum), in a large Colorado reservoir

Ecologically and economically valuable Pacific salmon and trout (Oncorhynchus spp.) are widespread and susceptible to the ectoparasite Salmincola californiensis (Dana). The range of this freshwater copepod has expanded, and in 2015, S. californiensis was observed in Blue Mesa Reservoir, Colorado, USA, an important kokanee salmon (O. nerka, Walbaum) egg source for sustaining fisheries. Few S. californiensis were detected on kokanee salmon in 2016 (<10% prevalence; 2 adult S. californiensis maximum). By 2020, age-3 kokanee salmon had 100% S. californiensis prevalence and mean intensity exceeding 50 adult copepods. Year and kokanee salmon age/maturity (older/mature) were consistently identified as significant predictors of S. californiensis prevalence/intensity. There was evidence that S. californiensis spread rapidly, but their population growth was maximized at the initiation (the first 2–3 years) of the invasion. Gills and heads of kokanee salmon carried the highest S. californiensis loads. S. californiensis population growth appears to be slowing, but S. californiensis expansion occurred concomitant with myriad environmental/biological factors. These factors and inherent variance in S. californiensis count data may have obscured patterns that continued monitoring of parasite–host dynamics, when S. californiensis abundance is more stable, might reveal. The rapid proliferation of S. californiensis indicates that in 5 years a system can go from a light infestation to supporting hosts carrying hundreds of parasites, and concern remains about the sustainability of this kokanee salmon population.     

Control of the bass tapeworm, Proteocephalus ambloplitis (Leidy), with mebendazole

Abstract. Mebendazole (methyl-5-benzoyl benziraidazole-2-carhamate) was shown to have anthelmintic activity against larvae of Proteocephalus ambloplitis (Leidy) in implantations were found to be highly effective. A single intraperitoneal injection of 200 mg/kg or a capsule implantation of 200 mg/kg of mebendazole each reduced the infection by 95 % after 6 weeks. Oral treatment for 14 consecutive days at 100 mg/kg/ day reduced I he infection by 90%. Intraperitoneal injection of 200 mg/kg of mebendazole ever, did not interfere with spawning and reproduction of largemouth bass; however fish injected with 300 mg/kg produced no fry. Haematocrit, total haemoglobin, total serum protein and histological changes were not evidenl in treated fish.     

Preferred temperature of grass carp, Ctenopharyngodon idella (Valenciennes), and brema carp, Megalobrama amblycephala (Yih), (Pisces, Cyprinidae) in horizontal and vertical gradients

The preferred temperatures of grass carp, Ctenopharyngodon idella (Valenciennes), and brema carp, Megalobrama amblycephala (Yih), were determined individually and together in both horizontal and vertical gradients. No significant difference was found by two methods between the preferred temperatures in either species of carp (28.0-28.5 ^oC) when the fish were placed individually. However, when the two species of carp were placed together, C. idella was displaced thermally, preferring a temperature of 23.5 ^oC, which was significantly lower than that obtained when it was held separately. This suggests that, if both species of carp are placed in ponds forming part of a Chinese polyculture system, C. idella will seek out a lower temperature as a mechanism to avoid competition, and therefore, the growth of this species will be reduced.     

Light and electron microscopic evidence of white spot disease in the giant tiger shrimp, Penaeus monodon (Fabricius), and the kuruma shrimp, Penaeus japonicus (Bate), cultured in Taiwan

Since 1992, mass mortalities among cultured giant tiger shrimp, Penaeus monodon (Fabricius), and kuruma shrimp, Penaeus japonicus (Bate), have been observed in Taiwan. The condition is known as 'white spot disease' (WSD), based on the characteristic white spots on the cuticle of diseased shrimp. With the scanning electron microscope, two sizes of white spots were observed. Each spot represented a protrusion on the inside surface of the carapace. The composition of white spots was similar to that of the cuticule, most calcium, as determined with an energy dispersive spectrometer. Histological studies of moribund, infected specimens revealed degenerated cells, characterized by hypertrophied nuclei, in various meso- and ectodermal tissues. Infected tissues included cuticular epidermis, connective tissue, lymphoid organ, antennal gland, and haematopoietic, gill and nervous tissue. Nuclei were Feulgen-positive and no occlusion body was found in the necrotic tissue. Transmission electron microscopy revealed the presence of rod-shaped and enveloped virions in the hypertrophied nuclei. The virions measured 298 ± 21 × 107 ± 8 nm in the giant tiger shrimp and 248 ± 12 × 104 ± 8 nm in the kuruma shrimp. In an experimental infection trial, cumulative mortality was 40% within 14 days under stress conditions. No mortality was observed in controls or in non-stressed infected shrimp. Experimental infections show that environmental stressors such as ammonia may enhance the severity of WSD virus infections in cultured shrimp.     

Lymphocystis infection in snakeskin gourami, Trichogaster pectoralis (Regan), (Anabantidae)

Abstract. A lymphocystis infection is described from aquarium-held snakeskin gourami, Trichogaster pectoralis (Regan). The cytoplasm of the hypertrophic cells revealed virus particles of extended hexagonal profiles with thin two-layered capsids. Subsequent examination of the fish 4 months later revealed hypertrophic cells showing varying degrees of collapse and degradation. The virus particles loading such cells were of regular hexagonal profiles with thick three-layered capsids.     

Quantifying the dietary niacin requirement of the Indian catfish, Heteropneustes fossilis (Bloch), fingerlings

A growth study was conducted to determine the dietary niacin requirement of the Indian catfish, Heteropneustes fossilis (Bloch), fingerlings (Mean weight 9.41 ± 0.18 g). Semi‐purified diets with five levels (0, 5, 10, 20 and 40 mg kg^?1 diet) of supplemental niacin were fed to H. fossilis for 15 weeks. Each diet was fed to three replicate groups of fish. Results indicated that the highest (P < 0.05) weight gain was for the fish fed the diet supplemented with 20 mg niacin kg^?1, followed by fish fed the diets with 40, 10 and 5 mg niacin kg^?1, and the lowest in fish fed the unsupplemented control diet. Patterns of specific growth rate (SGR) and protein efficiency ratio (PER) were similar to those of the weight gain. Survival of fish fed the control diet and niacin‐supplemented diet was 58% and 91–100% respectively. Niacin deficiency signs such as anaemia, anorexia, lethargy and skin haemorrhage were observed in fish fed the control diet. The haematocrit values (Ht) were higher (P < 0.05) in fish fed the diets supplemented with niacin than in fish fed the control diet. The hepatosomatic indexes (HSI) of fish fed with or without niacin‐supplemented diets were not significantly (P > 0.05) different from each other. Both body protein and lipid content were higher (P < 0.05) in fish fed the diet supplemented with 20 and 40 mg niacin kg^?1, respectively, than those fish fed other diets. The niacin content in liver significantly (P < 0.05) reflected the supplementation level in the diet and ranged from 29.11 to 40.31 mg g^?1 tissue. The associated liver niacin content for growth was about 47 μg g^?1 tissue. Quadratic regression analysis showed that the dietary niacin requirement for maximal growth of H. fossilis under these experimental conditions was about 25 mg kg^?1 diet.     

Fishery of the mangrove oyster, Crassostrea gasar, Adanson (1757), in the Lagos area,Nigeria

The mangrove oyster, Crassostrea gasar, constitutes an important source of animal protein among some communities in the Lagos area. This paper summarises present knowledge of the fishery of the mangrove oyster in the Lagos area, highlights its prospects, and suggests how oyster production for consumption can be improved.     

Feeding sequences (rotifer and dry diet), survival, growth and biochemical composition of African catfish, Clarias gariepinus Burchell (Pisces: Clariidae), larvae

The suitability of the freshwater rotifer Brachionus calyciflorus as starting food for the larviculture of African catfish, Clarias gariepinus Burchell, was investigated through studies of growth and fatty acid profiles in relation to different feeding sequences combining live food and dry diet in various proportions and during different mixed feeding periods. The best results for survival were observed when rotifers were supplied during the first week of feeding, i.e. sequences R₂ (exclusive supply of rotifers, then dry diet from day 8, onwards) and R₅ (50% rotifers+50% dry diet until day 7, then dry diet 100%), reaching 99.2% and 96.3%, respectively. The specific growth rate of larvae was largely dependent on the duration of preliminary feeding with the rotifers. A feeding with rotifers as a unique food source did not produce satisfactory growth during the first week of feeding. A precocious weaning showed that the highest growth rate and protein efficiency ratio (PER) can be obtained by feeding the larvae rotifers in association with a dry diet. The best PER and protein productive value (PPV) were recorded with feeding sequences R₂ and R₅. On the other hand, the series of polyunsaturated fatty acids was characterized by a relatively constant concentrations, and represented about 11.6% of the total fatty acids in sequence R₂ because of the presence of the acids of the linoleic series, which apparently originated from the food. The R₅ regime provided larvae with significant amounts of highly unsaturated fatty acids, such as linolenic acid C18:3n-3.     

Feeding selectivity of the seahorse,Hippocampus kuda (Bleeker), juveniles under laboratory conditions

This study examined the feeding selectivity of Hippocampus kuda juveniles under captive conditions and evaluates different food organisms that could be used to improve hatchery‐rearing of this species. Newly born H. kuda were reared for 10 days in 60‐L capacity tanks and fed rotifers (Brachionus rotundiformis), zooplankton (mostly Pseudodiaptomus annandalei and Acartia tsuensis) alone or both food sources. The size and amount of food ingested increased as seahorses grew. Selective feeding of seahorses appeared to change as they develop, preferring copepod adults over nauplii and rotifers. A. tsuensis was highly selected by juveniles over P. annandalei. Specific growth rate in terms of body weight (SGR‐BW, 15% day^–1) was the highest and mortality rate (9% at day 10) the lowest in seahorses fed a mixed food sources. Slowest growth rate (0.3% day^–1) and highest mortality rate (60% at day 7) were observed in seahorses fed rotifers alone. These results indicate that copepods are suitable food for seahorse juveniles, but a mixture of food organisms in the rearing tank environment enhances survivorship and growth of H. kuda, thus potentially providing a source of cultured rather than wild specimens for characterizing the life history of this threatened species.     

Diet of the largemouth bass, Micropterus salmoides (Lacepède), in Lake Naivasha, Kenya

Abstract The major food items of adult largemouth bass, Micropterus salmoides (Lacepède), in Lake Naivasha, Kenya are not markedly different from those in its native range. Although insects and their larvae are major components of the diet for both temperate and equatorial populations of juvenile bass, the equatorial population also eats Procambarus clarkii (Girard), juvenile fish and aquatic weeds. In temperate populations they also eat crustaceans, rotifers and oligochaetes. The frequency of occurrence of the major prey organisms in the stomachs of M. salmoides varies seasonally with population peaks in these organisms. Similar to North American populations, the Naivasha population feeds during the day between dawn and dusk. In contrast to temperate populations, the population of M. salmoides in this equatorial lake feeds throughout the year, with feeding intensity correlated with water temperature.     

Pathological findings in southern bluefin tuna, Thunnus maccoyii (Castelnau), infected with Cardicola forsteri (Cribb, Daintith & Munday, 2000) (Digenea: Sanguinicolidae), a blood fluke

Gills, heart ventricles and a limited number of other organs were collected from wild and captive southern bluefin tuna, and examined histologically for eggs of Cardicola forsteri . A limited number of entire hearts from farmed tuna were also examined, some of which yielded adult flukes within the ventricles. No adult flukes or their eggs were found in wild tuna. In infected farmed fish, fluke eggs impacted in the afferent filamentary blood vessels where they provoked a marked, but variable, inflammatory response, resulting in nodular gill lesions. No eggs were found on the efferent side of the gill vasculature, or in the compacta of the ventricle, which is supplied with blood from coronary vessels. The infection does not appear to cause mortality in farmed tuna.