Formation of Biogenic Amines in Delayed Salt-Cured Whole and Gutted Indian Oil Sardines (Sardinella longiceps)

The formation of biogenic amines in Indian oil sardines (Sardinella longiceps) collected from the Tuticorin coast of South India and treated with delayed salt-curing was investigated. Sardines were wet salt-cured in whole and gutted forms and examined in fresh and after 6, 9, 12, and 15 h delayed conditions at ambient temperature (32 ± 2°C) at four stages of salt-curing process for quality parameters and formation of biogenic amines. Moisture content decreased from 76% to 11.3% in salting followed by drying. Similarly, water activity reduced from 0.96 to 0.74 in salt-cured sardines. In contrast, total volatile base nitrogen content increased from 79 to 3,590 mg kg^–1 in salt-cured sardines. Halophilic count of sardines was higher (8 log cfu g^–1) after salting and decreased in drying stages. The 15 h delayed salt-cured whole sardines had higher histamine contents (1,568.27 mg kg^–1), cadaverine (4,059.84 mg kg^–1), putrescine (1,604.95 mg kg^–1), and tyramine (862.94 mg kg^–1) on the final day of drying. Whole sardines had higher biogenic amines and halophilic bacterial counts than the gutted sardines. The whole and gutted sardines salt-cured up to a delay of 6 and 12 h, respectively, at ambient temperature yielded the acceptable quality products with respect to biogenic amines.     

Oil sardine (Sardinella longiceps) off the Malabar Coast: density dependence and environmental effects

Marine fish stocks are known for extensive variation in landings, with temporal fluctuations attributable to density-dependent as well as environmental effects. In this paper we analysed a 44-yr time-series of oil sardine Sardinella longiceps landings from the Arabian Sea off the Malabar Coast of India. Density dependence was detected in the landings of oil sardine, reinforcing the potential for sustainable yields. Significant environmental factors (precipitation and sea level reflecting the strength of upwelling) during the monsoon period (June–August) are hypothesized to affect the dynamics of landings by influencing spawning and recruitment success. Together, density dependence and environmental variability during the monsoon explained 80% of the among-years variance in landings. Our results have important consequences for understanding catch variability and are potentially useful for facilitating management of this commercially important fishery.     

Fishery resources and economic gain in three mangrove areas on the south-east coast of India

Abstract The fishery resources and fishing income in three different mangrove areas were evaluated. The mangrove-rich area provided high catches of shellfish and finfish and yielded high fishery income, compared with the mangrove-poor areas. Luxuriant mangrove areas supported a catch of 11 kg shellfish ha⁻¹ day⁻¹ and 4.5 kg finfish ha⁻¹ day⁻¹, corresponding with an economic gain of US$ 14 (Rs 603.7) day⁻¹ for shellfish and US$ 3 (Rs 130.5) day⁻¹ for finfish. The value of maintaining mangroves to ensure better fishery resources and to support coastal economies was identified. Management practices for conserving and enhancing mangroves and associated fishery resources are suggested.     

Effects of increasing protein level on the performance,enzyme activity and body composition of the Brazilian sardine,Sardinella brasiliensis (Steindachner, 1879)

A six‐week growth trial was performed to estimate the dietary protein requirements for maximum growth of juvenile Brazilian sardine (Sardinella brasiliensis) based on growth performance, feed utilization, body composition and digestive enzyme activity. Six isoenergetic diets were formulated to contain protein levels that increased from 250 to 500 g/kg. Each diet was randomly assigned to triplicate groups of 160 fish with mean initial body weight of 0.93 ± 0.13 g, which were fed four times a day to apparent satiation. Growth tended to increase with the increase in the dietary protein level up to 400 g/kg. Total protein intake was indirectly correlated to apparent protein utilization. No significant differences in whole‐body composition were found between fish fed the different protein levels. Acid protease and neutral lipase activities did not show significant differences among the different protein dietary groups. Alkaline protease activity increased in fish fed up to 350 g/kg of protein and amylase activity in fish fed up to 400 g/kg. Using polynomial regression, 367 g/kg was estimated to be the optimum dietary protein requirement for maximum weight gain of juvenile Brazilian sardines.     

Incidence of white muscle disease, a viral like disease associated with mortalities in hatchery-reared postlarvae of the giant freshwater prawn Macrobrachium rosenbergii (De Man) from the south-east coast of India

Incidence of post‐larval mortalities of 30–100% was reported from commercial freshwater prawn, Macrobrachium rosenbergii (De Man) hatcheries in Andhra Pradesh and Tamil Nadu (south‐eastern states of India) since 2001. Infected postlarvae (PL) exhibited clinical symptoms with lethargy, anorexia and whitening of abdominal muscles and the disease was identified as white muscle disease (WMD). The waterborne infection of WMD was induced in the laboratory by exposing uninfected and healthy M. rosenbergii PL to the filtered muscle homogenates of the naturally infected PL, resulting in mortality that reached 99% within 10 days post infection. Histopathological examination of the infected animals revealed highly necrotic musculature. Degenerated muscle areas showed aggregations of melanized nuclei, many of which looked like inclusion bodies. Bacteriological examination of affected PL showed the presence of Staphylococcus spp. as a predominant organism, while laboratory challenge of healthy PL with this bacterial isolate did not reproduce WMD.     

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.     

Nutritional Evaluation of Indian Ocean Swimming Crab,Charybdis smithii (Portunidae), an Unconventional Crab Resource from the Indian Coast

Investigations were carried out to determine the nutritional profile of Indian Ocean swimming crab Charybdis smithii, which is emerging as an unconventional resource in trawl discards of India. The average protein content was 9.38 g/100 g, fat 0.86 g/100 g, ash 0.34 g/100 g, fiber 0.13 g/100 g, and carbohydrate 1.8 g/100 g. One-way analysis of variance showed no significant variations of constituents except in dry matter and carbohydrate between sexes. Macronutrients, Na (317.1, 327.6/100 g), K (148, 177.40 mg/100 g), Ca (187.90, 285.80 mg/100 g), and Mg (34.31, 41.49 mg/100 g), showed significant variation between sexes. The composition of micronutrients in male and female were Cu (0.28, 0.15 mg/100 g), Fe (0.57, 0.71 mg/100 g), and Zn (1.71, 2.75 mg/100 g). Mineral content showed significant difference between sexes. Amino acid analysis showed that 12.04 and 11.47 g/100 g essential amino acid glycine was present in male and female, respectively, and lysine concentration was 13.96 and 12.65 g/100 g, respectively. The nutritional profile of the species was determined the first time and shows that it is comparable with any other edible crabs and could be exploited as a commercial resource to supplement nutritional demand.     

Gametogenesis and spawning in the carpet-shell clam, Ruditapes decussatus (L.) (Mollusca: Bivalvia), from the Atlantic coast of Morocco

Abstract. Aspects of gametogenesis of the carpet-shell clam, Ruditapes decussatus (L.), in two lagoons on the Atlantic coast of north Morocco were studied during December 1986 to February 1988. The clams sampled did not show any sign of hermaphroditism and the percentage of males was 42%. The gonads started developing in mid-winter and were ripe in spring. Successive spawnings and reconstitution of gametes look place simultaneously starting from May up to the end of September. Two major spawning periods were noticed: a partial one in May-June and a complete spawning in August-September. From October to December the gonads were at resting stages. In coastal ecosystems where freshwater input is a very important factor, gametogenesis may be affected if clams are exposed to low salinities (less than 15%) for prolonged periods.     

Ichthyophonus hoferi Plehn & Mulsow in British Columbia stocks of Pacific herring, Clupea pallasi Valenciennes, and its infectivity to chinook salmon, Oncorhynchus tshawytscha (Walbaum)

Pacific herring, Clupea pallasi Valenciennes, collected from three areas of coastal British Columbia were screened for Ichthyophonus by histological examination. The infectivity of Ichthyophonus to juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum), was examined in laboratory studies. Ichthyophonus was detected in a total of 82 of 356 herring from all three areas. Prevalence in 2000 and 2001 ranged from 10.5 to 52.5% and was significantly lower in more northern (Hecate Strait) samples. Ichthyophonus was detected by histological examination in chinook salmon following oral or intraperitoneal (i.p.) exposure to homogenates of infected herring tissue. Infections in Yukon stock chinook salmon were occasionally associated with mortality and with inflammation in all tissues examined. Infections were detected significantly more frequently in the caecal mesenteries of i.p.-infected compared with oral-infected chinook salmon. The distribution and prevalence of Ichthyophonus isolates among diverse host species may assist in stock identification and in an improved understanding of trophic interactions.     

Determination of appropriate age and stocking density of vundu larvae, Heterobranchus longifilis (Valenciennes 1840), at the weaning time

Two experiments were conducted in order to determine the appropriate age and stocking density of vundu catfish Heterobranchus longifilis at the weaning time. In the first experiment, five triplicate groups of 100 larvae (initial mean weight=3.4 mg) per aquaria were stocked from first feeding [day 3 post‐hatch (p.h.)] to day 30 p.h., and then weaned, on days 3 (W3), 5 (W5), 8 (W8) and 14 (W14), and an unweaned group (An). Significant differences were observed in growth, survival, cannibalism, coefficient of weight variation and body composition among larvae weaned at different ages and the control group. The later the larvae were weaned, the better were the growth performances [final mean weight: from 65.1 to 201.1 mg and specific growth rate (SGR): from 11.0 to 15.2% day^?1] and the survival (from 36.5% to 74.3%). The experiment with stocking densities of 5, 10, 25 and 50 larvae L^?1 showed that increasing the stocking density decreased growth performances and weight variation but improved the survival rate of larvae. The best growth performances (SGR=13.4 and 11.4% day^?1) with the lowest survival rates (70.3% and 77.3%) were observed in larvae stocked at densities of 5 and 10 larvae L^?1 respectively.     

Genetic basis of pectoral fin deformities in the African catfish Clarias gariepinus (Burchell, 1822), Heterobranchus longifilis (Valenciennes 1840) and their hybrids

Morphological aberrations of the pectoral fins in nine mating combinations involving Clarias gariepinus (Burchell, 1822), Heterobranchus longifilis (Valenciennes, 1840) and their hybrids were investigated to determine the level and genetic basis of occurrence. The highest mean percentage survival in a Clarias× Clarias group was 75%, whereas the least mean percentage survival was 2% in the same group. The least mean percentage survival (40.3%) in the remaining three groups occurred in the cross of female hybrid (right pectoral fin absent) × male C. gariepinus (right pectoral fin absent). A maximum of nine types of aberrations was observed in the four mating groups – double dorsal fin, curved posterior dorsal fin, spineless right pectoral fin, right pectoral fin absent, left pectoral fin absent, rudimentary pectoral fin, both pectoral fins absent, double anal fin and curved anterior dorsal fin. These nine aberration types were recorded in the Clarias× Clarias group, with a total frequency ranging from 7.14% to 75.00%. The least number of aberrations was observed in the hybrid ×Clarias group (double dorsal fin and both pectoral fins absent) with a frequency range of 1.47–5.55%. No aberration was observed in two crosses involving female hybrid (right or left pectoral fin absent) × female C. gariepinus (normal). The level of aberrations in some of these crosses indicates the involvement of genotype rather than the influence of environment.     

Modelling of nitrogen loads from the farming of yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

Farming of yellowtail kingfish ( Seriola lalandi , Valenciennes, 1833) in the coastal waters of Australia is a relatively new aquaculture industry, and little is known about the magnitude of nutrient discharges from individual pens. In this work, we modelled the flow of nitrogen for each of two commercial pens in Fitzgerald Bay, upper Spencer Gulf, South Australia. The fish were fed commercial pellets with feed conversion ratios (FCRs) between 3.0 and 3.2 (dry weight feed/wet weight growth). These high values of FCR were reflected in the high nitrogen loads to the environment (176–195 kg N tonne⁻¹ growth) and a small retention of nitrogen in fish growth (14–16% of feed inputs). Considering an annual production of 2000 tonnes, total loads to the environment can reach 391 tonnes N year⁻¹. Eighty-two per cent of these loads are expected to be lost to the water column as dissolved wastes. The high nutrient loads and the importance of dissolved wastes compared with other aquaculture species, such as salmon and trout, reflect the distinctly higher metabolic rates of this pelagic predatory species. The nature of the wastes suggests low localized impacts at current production levels, but regional effects remain unknown.     

Pathology and mass mortality of Pacific oysters, Crassostrea gigas (Thunberg), in 2005 at the East Frisian coast, Germany

In 2005, Pacific oysters, Crassostrea gigas , were collected from May to September along the East Frisian coast and processed for histology. Because of mass mortalities in September, additional samples of moribund oysters and apparently healthy blue mussels, Mytilus edulis , were subjected to virological and ultrastructural investigation. The oysters displayed a variety of pathological conditions including viral gametocytic hypertrophy which is reported here for the first time from the German coast. Haemocyte aggregations in the digestive tract, in the intestinal mucosa and submucosa, in the mid-gut gland and in the ventricle of the heart were commonly observed at some stations. In association with mass mortalities, severe gill necrosis occurred which may have contributed to the high mortality rates. Total mortality rates of up to approximately 60% were seen. All size classes and thus age classes of oysters were affected, with highest mortality rates within the youngest age classes which had just reached sexual maturity (shell lengths <40 mm). The smallest dead oysters had shell lengths of 10 mm. The phenomenon was mainly restricted to C. gigas stocks in harbours, probably because of favourable conditions for infection, i.e. limited water exchange, less food availability, reduced oxygen content and higher pollution levels.     

On condition index and percentage edibiliy of the shortneck clam Paphia malabarica (Chemintz) from estuarine regions of Ratnagiri,west coast of India

Paphia malabarica is an important clam species, which has formed vast beds in the Kalbadevi estuary (Shirgaon creek) and Kajali estuary (Bhatye creek), Ratnagiri. They are exploited here commercially throughout the year for local as well as external markets due to the heavy demand. This study was undertaken to assess seasonal variations in the quality of the meat of clams by estimating the condition index and percentage edibility. Higher values were recorded during the monsoon (June–August). A rapid decline was observed in the edibility values from November onwards. Higher condition index and percentage edibility were recorded from June to November, indicating the high quality of clam meat.     

Studies on pathogenicity and prevalence of white spot syndrome virus in mud crab, Scylla serrata (Forskal), in Zhejiang Province, China

Mud crab, Scylla serrata (Forskal), is the most commercially important marine crab species in China. In recent years, serious diseases have occurred in major mud crab culture regions in SE China. PCR detection of white spot syndrome virus (WSSV) in diseased mud crabs collected from Zhejiang Province during 2006–2008 showed a prevalence of 34.82%. To study the pathogenicity of WSSV to mud crab, healthy mud crabs were injected intramuscularly with serial 10‐fold dilutions of a WSSV inoculum. The cumulative mortalities in groups challenged with 10^?1, 10^?2, 10^?3 and 10^?4 dilutions were 100%, 100%, 66.7% and 38.9% at 10 days post‐injection, respectively. All moribund and dead mud crabs except the control group were positive for WSSV by PCR. Based on the viral load of the WSSV inoculum by quantitative real‐time PCR, the median lethal dose (LD50) of WSSV in S. serrata was calculated as 1.10 × 10⁶ virus copies/crab, or 7.34 × 10³ virus copies g^?1 crab weight. The phenoloxidase, peroxidase and superoxide dismutase activities in haemolymph of WSSV‐infected moribund crabs, were significantly lower than the control group, whereas alkaline phosphatase, glutamate‐pyruvate transaminase and glutamic‐oxaloacetic transaminase were higher than in the control group. WSSV was mainly distributed in gills, subcuticular epithelia, heart, intestine and stomach as shown by immunohistochemical analysis with Mabs against WSSV. The epithelial cells of infected gill showed hypertrophied nuclei with basophilic inclusions. Numerous bacilliform virus particles were observed in nuclei of infected gill cells by transmission electron microscopy. It is concluded that WSSV is a major pathogen of mud crab with high pathogenicity.     

Full‐length cloning and phylogenetic analyses of translationally controlled tumour protein and ferritin genes from the Indian white prawn,Fenneropenaeus indicus (H. Milne Edwards)

Elucidation, through molecular analyses, of bacterial afflictions in commercially important aquaculture‐reared shrimps is pivotal for the prevention and/or control of disease outbreaks. In this study, we examined the phylogenetic relatedness and compared the possible immune‐related functional roles of both translationally controlled tumour protein (TCTP) and ferritin genes with previous studies. Both TCTP and ferritin genes were substantially upregulated in the Indian white prawn, Fenneropenaeus indicus (H. Milne Edwards), post‐larvae following bath challenge with the virulent strain of bacteria, Vibrio harveyi D3. Full‐length cloning of these genes by rapid amplification of complementary DNA ends ‐polymerase chain reaction (RACE‐PCR) yielded 727‐base pair (bp)‐long TCTP and 1212‐bp‐long ferritin gene sequences. Their open reading frames (ORFs) were 507 and 510 bp, respectively. The TCTP‐ORF coded for 168 amino acids with three substitutions at positions 37, 141, 155, and the ferritin ORF coded for 170 amino acids with no species‐specific substitutions. Phylogenetic analysis suggested the closest relatedness of both TCTP and ferritin from F. indicus to Chinese white prawn, Fenneropenaeus chinensis (Osbeck). In addition to reporting the full‐length sequences of these immune‐relevant genes, this study highlighted their conserved natures, which perhaps make them important defence‐related proteins in the innate immune system of F. indicus.     

Characterization of cellulase-producing bacteria from the digestive tract of tilapia, Oreochromis mossambica (Peters) and grass carp, Ctenopharyngodon idella (Valenciennes)

Isolation and characterization of cellulase‐producing aeorobic bacterial flora in the intestine of omnivorous tilapia (Oreochromis mossambica) and phytophagous Chinese grass carp (Ctenopharyngodon idella) have been carried out using selective carboxymethylcellulose‐agar (CMC‐agar) medium. The cellulolytic activity was measured both qualitatively and quantitatively. It was found that the ability of different strains in degrading cellulose varies within a wide range. Among the strains isolated from the gut of each test fish, TM1 and CI3 isolated from O. mossambica and C. idella, respectively exhibited maximum cellulolytic activity (67.02 and 35.8 U mL^?1 respectively). Pure cultures of these strains were selected for morphological, physiological and biochemical characterization. On the basis of these tests, the isolated strains were identified as Bacillus circulans (TM1) and Bacillus megaterium (CI3). Both the strains are rod‐shaped, motile and show better temperature (15–42°C) and pH (5–11) tolerance. The selected strains were further quantitatively assayed for amylase and protease activities. Maximum amylase and protease activities were exhibited by TM1 and CI3 respectively. Information generated from the present study might contribute towards better‐feed formulation incorporating plant ingredients.     

Identification and pathogenicity study of emerging fish pathogens Acinetobacter junii and Acinetobacter pittii recovered from a disease outbreak in Labeo catla (Hamilton, 1822) and Hypophthalmichthys molitrix (Valenciennes, 1844) of freshwater wetland in West Bengal,India

The disease outbreaks in aquaculture system of wetlands are the major cause of fish mortality. Among various bacterial septicaemic diseases, fish mortality caused by Acinetobacter spp. is recently reported in different fish species. Fish disease outbreak was investigated in a wetland of West Bengal, India to identify the aetiological factors involved. The moribund fish were examined and subjected to bacterial isolation. Two bacterial causative agents were identified as Acinetobacter junii and Acinetobacter pittii by biochemical characterization and 16S rRNA gene amplification. Both the isolates were oxidase‐negative, nitrate‐negative, catalase‐positive and indole‐negative. The molecular identification using 16S rRNA gene sequencing and phylogenetic tree analysis further confirmed the two Acinetobacter spp. with 97%–99% similarity. The antibiotic resistance patterns of these two bacteria revealed that both of them were resistant to β‐lactam, cefalexin, cephalothin, amoxyclav, cefuroxime, cefadroxil, clindamycin, vancomycin and penicillin. In addition, A. pittii was also resistant to other antibiotics of cephams group such as ceftazidime and cefotaxime. In the challenge experiment, both A. junii and A. pittii were found to be pathogenic with LD₅₀ of 1.24 × 10⁵ and 1.88 × 10⁷ cfu/fish respectively. Histopathological examination of gill, liver and kidney revealed prominent changes supporting bacterial septicaemia. The investigation reports for the first time on concurrent infection by A. junii and multidrug‐resistant (MDR)‐A. pittii as emerging fish pathogens to cause severe mortality in Labeo catla and Hypophthalmichthys molitrix in a freshwater wetland.