“Wild fish are a blessing”: changes in fishing practices and folk fish cuisine around Laguna Lake, Northern Philippines

Several coastal communities rely heavily on wild-caught fish for personal consumption and their livelihoods, thus being sensitive to the rapid global change affecting fish availability. However, in the last century, aquaculture has been increasingly adopted. To understand the uses and changes of wild-caught fish, we conducted 30 semi-structured interviews with fishers of Laguna Lake, Philippines. Fishermen, with up to 60 years’ experience, reported catching 31 fish species as a staple food. The taxa with the greatest variety of food uses were the farmed Oreochromis aureus, and the wild Channa striata and Cyprinus carpio. Fish was boiled, fried, grilled and dried, and over 20 different local dishes were reported. Fishers reported that local communities previously relied more on wild fish, while today a greater proportion of consumed fish comes from aquaculture fish species such as Oreochromis aureus and Hypophthalmichthys nobilis. Wild fish remains a crucial aspect of local gastronomic diversity, underpinning the biodiversity of the Laguna Lake, while also representing an important element for food sovereignty. The study stresses the need to sustain local ecological knowledge to ensure the ecological, social and economic sustainability of the communities.

Bioaccumulation of PCBs and PBDEs in Fish from a Tropical Lake Chapala, Mexico

Lake Chapala is the largest natural freshwater reservoir in Mexico and the third largest lake in Latin America. Lakes are often considered the final deposit of polluting materials; they can be concentrated in the organisms that inhabit them, the water, and the sediments. The PCBs and PBDEs are environmental pollutants highly studied for their known carcinogenic and mutagenic effects. PCB and PBDE bioaccumulation levels were determined in Chirostoma spp., Cyprinus carpio, and Oreochromis aureus. In addition, we monitored the concentrations of PCBs and PBDEs in sediment and water from Lake Chapala were monitored. Samples were collected during two periods, in October 2018 and May 2019. The samples were analyzed by gas chromatography coupled with mass spectrometry. Two bioaccumulation factors were determined in fish, one in relation to the concentration of PCBs and PBDEs in sediments and the other in relation to the concentration of PCBs and PBDEs in water. The PCB levels were 0.55–3.29 ng/g dry weight (dw) in sediments, 1.43–2.98 ng/mL in water, 0.30–5.31 ng/g dw in Chirostoma spp., 1.06–6.07 ng/g dw in Cyprinus carpio, and 0.55–7.20 ng/g dw in Oreochromis aureus. The levels of PBDEs were 0.17–0.35 ng/g dw in sediments, 0.13–0.32 ng/mL in water, 0.01–0.23 ng/g dw in Chirostoma spp., 0–0.31 ng/g dw in Cyprinus carpio, and 0.1–0.22 ng/g dw in Oreochromis aureus. This study provides information for a better understanding of the movement, global distribution, and bioaccumulation of PCBs and PBDEs. The results show that the fish, water, and sediments of Lake Chapala are potential risks to the biota and the local human population.

Trophic relationships among fourteen native and non-native fish species in the Shatt Al-Arab River, Iraq

The present study objectified to evaluate the trophic relationships among 14 fish species (10 natives and 4 non-natives) in the Shatt Al-Arab River, considering the trophic niche breadth and the diet overlaps of the species. The food items in the stomach of each species are determined by adopting the index of relative importance (IRI). The dietary analysis revealed a total of 12 types of major food items consumed (which represent >10% IRI). Two species (Oreochromis aureus and Cptodon zillii) were herbivores consumed mostly macrophytes, algae and diatoms. Four species (Planiliza abu, P. klunzengeri, P. subviridis and Osteomugil speigleri) were herbivores mainly fed on diatoms, macrophytes, detritus and algae. Three species (Carasobarbus luteus, Carassius auratus and Cyprinus carpio) were omnivores mostly consumed macrophytes, detritus, diatoms and algae. Two species (Tenualosa illisha and Nematalosa nasus) were filter feeders fed largely on zooplankton, algae, detritus and macrophytes. Three species (Acanthopagrus arabicus, Johnius belangerii and J. dussumeiri) were carnivores mainly preyed on shrimps, crabs and fish. Levin’s index diet breadth analyses divided the studied fish species into three categories; two species with high specialization, five species with low specialization, and seven species with generalization feeders. The dietary composition of fish species exhibited 62 diet overlaps as indicated by the Jaccard index, eight of them high, 36 moderate and 18 low overlaps. Only J. dussumeiri and J. belangerii have no diet overlap with other species. Overall, the study demonstrates that most trophic overlaps between species were moderate, but high degree overlap was between the native species (C. luteus) and invading species (C. auratus) and therefore strengthen earlier conclusions regarding interspecific competition between these two species.

Growth, length-weight relationship, and condition factor of NIFI (Oreochromis sp.) and Srikandi Tilapia (Oreochromis aureus x niloticus) at the grow-out stage in the high salinity brackishwater ponds

Tilapia strain of NIFI (Oreochromis sp.) and Srikandi (Oreochromis aureus x niloticus) are superior strain of tilapia that able to grow well in brackish water ponds. However, an increasing water salinity might have an impact on a series adaptation process on fish that leads to various morphological changes. This study aimed to analyze the growth and length-weight relationship of both tilapia strain in brackishwater pond with salinity of 25-30 ppt. Research was conducted in brackishwater pond in Losari, Brebes Regency. Fish were reared in 5x5x1 m3 hapas installed in the pond for four months. At the end of experiment period, body length and weight measurement were carried out for 26 males and 34 females of NIFI strain and 31 males and 28 females of Srikandi strain. The result showed that the highest growth rate was shown by Srikandi strain and the highest length was shown by NIFI. Positive allometric growth was found in the Srikandi females, while Srikandi males as well as NIFI tilapia males and females showed a negative allometric growth. Length-weight relationship on males and females of NIFI strain followed the formula of W = 0.0583L2,632 and W = 0.0452L2,665, respectively. Whereas, on males and females of Srikandi strain followed the formula of W = 0.0358L2,8545 and W = 0.0287L3,1580, respectively. There was a strong correlation between length and weight of fish from both strains with the R2 value ranged between 0.80 – 0.87. Condition factor of males and females of NIFI were 1.853 and 2.009, while Srikandi tilapia males and females were 2.308 and 2.665, respectively. Red NIFI and Srikandi tilapia are able to adapt in a high salinity level of brackish water pond.

Recent status of exotic tilapia species in Turkey

One of the most controversial issues in Turkey about the occurrence of the exotic fish species belonging to the family Cichlidae. Up to date, starting the 1970’s a total of seven species including Coptodon rendalli, C. zillii, Oreochromis aureus, O. mossambicus, O. niloticus, Sarotherodon galilaeus and Tristramella simonis introduced to Turkey for aquaculture purposes or accidently. Then these species have deliberately released or escaped from research and aquaculture facilities establishing themselves into natural environment of Turkey. In other cases, tilapia have been introduced into new aquatic habitats via aquarists or ornamental fish farmers. There was not any reliable record about establishment of O. mossambicus, S. galilaeus and T. simonis in Turkey. It is observed that now C. rendalli, C. zillii, O. aureus, and O. niloticus and/or hybrids of them exist in the wild water system of Turkey. Another problematic issue is that species identification of specimens found in nature is impossible due to the fact that hybridization of different species of Cichlidae. By the way, the range of the species belonging to the family Cichlidae in Turkey is determined that a need for detailed genetic studies to assess the current status.

Accumulation of heavy metals in tilapia fish species and related histopathological changes in muscles, gills and liver of Oreochromis niloticus occurring in the area of Qahr El-Bahr, Lake Al-Manzalah, Egypt

Accumulation of metals (Fe, Zn, Cu, Mn, Pb, Cd and Ni) in the muscles and gills of Oreochromis niloticus, Oreochromis aureus and Tilapia zillii was assessed based on seven locations in the Qahr El-Bahr area in Lake Al-Manzalah. The average accumulation of metals was in the following order: Tilapia zillii > Oreochromis aureus > Oreochromis niloticus. To determine the risk of fish consumption, the estimated daily intake, carcinogenic, non-carcinogenic and relative risk indices were calculated. The results indicate that the intake of individual metals through the consumption of fish is almost safe for human health, whereas the intake of combined metals poses a high potential health risk to consumers. Assessment of carcinogenic risk of Cd and Ni from the consumption of tilapia species indicates that consumers are at risk of cancer. The contribution of Pb and Cd to the overall relative risk index ranged from 34% to 41%. Of the three species studied, Oreochromis niloticus is relatively safe for consumption as it poses the least health hazard, while Tilapia zillii is more predisposed to accumulate metals in its tissues. Histopathological changes were observed in the muscles, gills and liver of Oreochromis niloticus as a result of heavy metal accumulation in these organs.

Regulatory elements in the upstream region of metallothionein gene in tilapia species

Tilapia is a hardy fish which can survive in water bodies polluted with heavy metals. Metal resistance is conferred by higher expression of metallothionein gene (mt) in many organisms. Level, time and tissue-specificity of gene expression is regulated through transcription factor binding sites (TFBS) which may be present in the upstream, downstream, or even in the introns of a gene. So, as a candidate regulatory region, the 5’upstream sequence of mt gene in three tilapia species, Oreochromis aureus, O. niloticus and O. mossambicus was studied. The targeted region was PCR-amplified and then sequenced using a pair of custom-designed primer. A total of only 2.7% variation was found in the sequenced genomic region among the three species. Metal-related TFBS were predicted from these sequences. A total of twenty eight TFBS were found in O. aureus and twenty nine in O. mossambicus and O. niloticus. The number of metalrelated TFBS predicted in the targeted sequence was significantly higher compared to that found in randomly selected other genomic regions of same size from O. niloticus genome. Thus, the results suggest the presence of putative regulatory elements in the targeted upstream region which might have important role in the regulation of mt gene function. Dhaka Univ. J. Biol. Sci. 30(1): 95-103, 2021 (January)

Fish Assemblages in Iraqi Marine Waters, North West The Arabian Gulf

The composition of fish assemblages in Iraqi marine water was assessed. 91 species belonging to 71 genes and 47 families of Osteichthyes and 13 species of Conderchthyes were collected during the study period from January to December 2018, using trawl net fishing. Three stations were selected, where two new species (Siganus javus and Gobiopsis sp.) and reclassification of Torpedo panthera where identified and two species of freshwater fish (Oreochromis niloticus and Oreochromis aureus) were first recorded in marine waters. The highest numbers of species were 32 and 42 for the first and second stations, respectively, recorded in October , while 55 species were recorded in the third station during August. Leiognathus bindus was the dominant species in the first and second stations, while Ilisha compressa dominated the third station. Carangidae and Sciaenidae were the dominant families in number of species (7 and 5, respectively), whereas 4 species were recorded for Clupeidae, Sparidae, Mugilidae and Gobidiae.

Variations in Hybrid Combinations Lead to Differences in Mitochondrial Inheritance

BackgroundWhile tilapia are the second most farmed group of fish in the world, the Oreochromis niloticus (♀) × Oreochromis aureus (♂) hybrid is one of the most frequently observed tilapia crosses in China. Based on its conservative nature and maternal inheritance pattern, mitochondrial DNA is often used in kinship analysis. Evidence of paternal inheritance has been noted in some animal species. ResultsThe mitochondrial CoI and Cytb genes, and D-loop gene regions of Oreochromis niloticus and Oreochromis aureus fish were sequenced and aligned to their orthogonal and backcrossed offspring. As evidence of paternal mitochondria DNA inheritance was found, the whole mitochondrial genome was then sequenced. Results showed that in the Oreochromis niloticus (♀) × Oreochromis aureus (♂) hybrids, certain fish shared 92.88% of the maternal mitochondria genome, and 99.86% with the paternal mitochondria genome. This implied that there was paternal mtDNA inheritance. However, all Oreochromis niloticus (♂) × Oreochromis aureus (♀) hybrids had 100% identical mitochondria genome with their female parent. ConclusionsThe study showed that while paternal mtDNA inheritance occurred in the Oreochromis niloticus (♀) × Oreochromis aureus (♂) hybrid, this did not happen in Oreochromis niloticus (♂) × Oreochromis aureus (♀) offspring. This implies that in hybrid species, different hybridization combinations might provide an explanation for paternal mtDNA inheritance pattern.