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Status of Taal Lake Fishery Resources with Emphasis on the Endemic Freshwater Sardine, Sardinella tawilis (Herre, 1927)
Get PDFAssessment of fisheries in Taal Lake was conducted from 1996-2000 and 2008-2011 to know the status of the commercially important fishes with emphasis on the endemic freshwater sardine, Sardinella tawilis. Results of the fish landed catch survey in 11 coastal towns of the lake showed a decreasing fish harvest in the open fisheries from 1,420 MT to 460 MT in 1996 to 2011. Inventory of fisherfolk, boat, and gear also decreased to 16%, 7%, and 39%, respectively from 1998 to 2011. The most dominant gear is gill net which is about 53% of the total gear used in the lake with a declining catch per unit effort (CPUE) of 11kg/day to 4 kg/day from 1997 to 2011. Active gear such as motorized push net, ring net, and beach seine also operated in the lake with a CPUE ranging from 48 kg/day to 2,504 kg/day. There were 43 fish species identified in which S. tawilis dominated the catch for the last decade. However, its harvest also declined from 744 to 71 mt in 1996 to 2011. The presence of alien species such as jaguar fish, pangasius, and black-chinned tilapia amplified in 2009.
Population parameters of S. tawilis from 2009 to 2011 were estimated using the FiSAT (FAO-ICLARM Stock Assessment Tool) software. The analysis of length frequency data showed an estimated L∞ of 15.40 to 16.36 cm and K value ranged from 0.53 to 0.73. The total mortality (Z) ranged from 3.01 to 5.03, natural mortality (M) from 1.44 to 1.75, fishing mortality (F) from 1.57 to 3.28 and exploitation rate (E) from 0.52 to 0.65. The high values of fishing mortality and exploitation rates indicate unsustainable fishing practices. Conservation and management measures of the fishery resources in the lake were recommended for appropriate action of the Protected Area Management Board (PAMB
Modelling trophic structure and energy flows in the coastal ecosystem of the Persian Gulf using Ecopath with Ecosim
Get PDFIn the present study, the trophic structure for some species of the coastal ecosystem of south of the Qeshm Island was developed using the mass balance modeling software Ecopath (Version 6.5.1). In this model, 33 functional groups including fish, benthos, phytoplankton, zooplankton, seaweed and detritus were simulated. In total, 3757 samples of stomach contents were analyzed based on the weight and numerical methods. Bony fish and crustacean were found to be the main prey in most of the stomach contents. The mean trophic level in the study area was calculated to be 3.08. The lowest trophic level was belonged to Liza klunzingeri, (2.50) and the highest belong to Trichiurus lepturus (4.45). The range of total mortality varied from 1.11 per year for T. Lepturus to 3.55 per year for Sillago sihama. The lowest and highest Consumption/Biomass value was belonged to Trichiurus lepturus (2.94) and Rastrelliger kanagurta (11.60) respectively. In this study, the role of ecological groups in the food web was determined using Keystone Index. The results showed that benthos and subsequently phytoplankton and zooplankton are among the dominant ecological groups in the southern ecosystem of Qeshm Island. The Connectance Index and the System Omnivory Index of this ecosystem were estimated to be 0.14 and 0.15 respectively. Population dynamics studies especially the exploitation rate (E) showed that Pomadasys kaakan, Rastrelliger kanagurta and Sillago sihama are under fishing pressure. Overall, the indices of ecological relationships with the population dynamics parameters showed that the exploitation of the fisheries resources in the study area is not in a good condition. The results of Ecosim model using time series of mean biomass from 2004-2016, showed a decrease in the biomass of Nemipterus japonicus, Otolithes ruber and Rastrelliger kanagurta. In general, the results of this study showed that the current fish harvest on the population of carnivorous species is very high which in long term could decrease the number of fish recruitment and consequently the capacity and sustainability of Qeshm Island fishing. Moreover, the high exploitation of fishing resources in this area could have negative effect on top-down food web and gradually reduce the top predator species, and eventually resulted in changing the trophic level of the species and reduction of the top of the food web species, which could be resulted in damaging of the ecological balance and endangering long-term sustainable utilization
Assessment of dominant species food relation in habitats of commercial shrimp in Hormuzgan Province waters (Persian Gulf)
Get PDFShrimp is one of the most important aquatic animals,that have decreased their stocks in Hormozgan province, especially the eastern province . Evalution of food interaction in shrimp habitats (Estuaries of Tyab, Yek shabeh, Laft and Khouran) was studied with Ecopaht with Ecosim software (ver. 6.5) in Hormuzgan province. After entering the input components (Biomass,P/B and Q/B), model was balanced and outputs were extracted. Results of trophic levels, was close to previous research in these areas for all species in estuaries. Maximum of ecotrophic efficiency was belonged to phytoplankton and other preys that were observed in predator stomachs. Biological future of food web estimated to be threatened based on omnivore index of planktonivore groups. Maximum food competition between the four food models was estimated in detritivores communities in Laft estuary, that may be related to the low density of mangrove in this region. Khamir estuary ecosystem could be more stable, because each impacting group had its own separate ecological niche and special predation territory. key indices in each of four food models were related to phytoplankton communities, this key role has been demonstrated much better in Yek Shovy estuary than others. Future of commercial shrimp stocks will be expected to be in better condition in Khoran estuary compared to other three ones, due to selection of separate ecological niche by predators and High biomass of detritus in this estuary
Study on bioaccumulation of Aldrin, Diazinon and Endrin pesticides in the edible muscle tissues of commercially important fish species of the Anzali Wetland
Get PDFThe objectives of the present investigation were to study the bioaccumulation of Aldrin, Diazinon and Endrin pesticides in the edible muscle tissues of Tinca tinca, Rutilus frisii kutum, Carassius auratus, Cyprinus carpio, Silurus glanis and Esox lucius that were caught at various stations in the west, east and center of the Anzali Wetland and to compare the results with the standards of the World Health Organization (WHO). The concentration of organochlorine pesticide was determined using Gas Chromatography (GC) equipped with an electron capture detector. The concentration of organophosphorus pesticide was determined using Gas Chromatography/Mass Spectrometry (GC/MS). The highest concentration of Diazinon was detected in Esox lucius from the wetland east station (20.25 ppb). Significant differences were not observed in the amounts of Diazinon and Aldrin pesticides in the muscles of fish samples in various stations (P>0/05). The highest amounts of Endrin were observed in the muscle of Cyprinus carpio from the wetland east and west stations which were significantly different compared to that of other fish species (P<0/05). The amount of Aldrin in the Carassius auratus was significantly different compared to that of other fish species (P<0/05). According to the results, the amounts of Aldrin, Diazinon and Endrin were lower than the detection limits of the WHO standards. Therefore, consumers are not at risk from the point of view of food safety
Investigation and determination of some heavy metals in the Aras river fish species in the East Azerbaijan Province (2015-16)
Get PDFThis study was conducted to determine heavy metals (Cu, Mo, As, Hg) in fish species of Aras River (East Azerbaijan) at four stations (From Julfa to 25km after Nourdos border) during four seasons from 2015 to 2016. Thirty eight specimens of fish were collected by using of electrofishing as the main method for sampling. The amounts of heavy metals were measured by using an atomic spectrophotometer in the muscle tissue of specimens. Bioaccumulation factor was also calculated for each species. The amount of bioaccumulation factor for molybdenum was the highest and the arsenic had the lowest amount. The highest concentration of copper was in Barbus lacerta with a mean of 13.6 ± 11.3μg /g dry weight and for the molybdenum, Alburnoides bipunctatus had the highest mean concentration (11.7±4.9) μg / g dry weight. The average concentration of mercury (13.1 ± 1.5 μg / kg dry weight) was highest in Alburnus alburnus. Regarding the arsenic elements, as it was analyzed in a small number of specimens, the highest concentrations were recorded in Alburnoides bipunctatus. According to ANOVA, there were a significant difference between mean concentration of copper in different species (p<0.05) and the Duncan test has distinguished Alburnus alburnus from other species
Comparison of qualitative characteristics of fish paste produced from minced kilka (Clupeonella cultriventris) and silver carp (Hypophthalmichthys molitrix)
Get PDFThe aim of this study was to determine the qualitative characteristics of ready-made fish paste made from minced meat (Clupeonella cultriventris) and silver carp (Hypophthalmichthys molitrix) and its shelf-life at a refrigerated temperature.This compilation was performed in five treatments including amounts 100, 75, 50 and 25 percent of processed fish meat were cured. The treatments were packed in heat-resistant glass after pasteurization. Samples were stored at 4oC for 40 days.The amount of TVB-N in the experimental treatments during the course of the change was increased that this factor varied between15.25-31.25 mg/100 g of meat in experimental treatments. This factor was in the 100% rolled silver carp treatment until the end of the shelf life in the standard range. The amount of tybarbibacteric acid increased during storage period varied between 0.13- 2.11mg malondialdehyde/1000g in experimental treatments, but this factor was in the 100% treatment of silver carp paste after the end of the maintenance period in the standard range (less than 1.8 mg/100gr), in other treatments, after 30 days, was more than standard limitation. The pH changes in treatments did not significantly decrease (P>0.05), this factor varied between 5.05 to 5.93 in the experimental period. Total bacterial counts, psychrophilic bacteria and coliform and molds were not observed in experimental treatments during storage period. Microbial contamination was not observed during the storage period in the refrigerator in the experimental treatments. The taste and texture in silver carp treatment (100%) were better than other treatments. The ash, protein and fat in 5 treatments did not significantly change during storage (p>0.05). The moisture content was not significantly increased in all five treatments during storage (p>0.05). Results showed treatment of processed carp (100%) was better than other treatments (p<0.05)
Efficiency of fishing gear used for king fish fishery with the emphasize on gill nets in Oman Sea- coastal waters of Sistan and Baluchestn Province
Get PDFEfficiency of various meshes of gillnets and trolling gear was investigated for catching kingfish (Scomberomorus commerson) in coastal waters of Sistan and Baluchestan province in 2007. In gillnets with mesh sizes between 57 to 110 mm and netting of monofilamnet and multifilament, the size distribution of kingfish ranged between 40 to 78 cm of fork length, which all specimen caught were immature. In mesh size of 146 mm and 171 mm, the length range of the species was larger, in which the frequency of immature fish for the respective mesh sizes was 19 and 11. In general, most fish was captured by wedging in the all mesh sizes. The size range of kingfish captured by the trolling was between 52 and 147 cm, of which more than 50 percent of caught fish were immature. The proportion of kingfish catches in the gillnets of 57-110 mm mesh sizes is about 13% of the total catch composition, for which the mesh sizes are considered as the dominant gillnets for capturing the species in this area. The conribution of kingfish catches in 133, 146, and 171 mm mesh sizes was 1.1, 52.3 and 18.9% respectively, with a 146-mm mesh size is considered as a dominant gillnet for this species. The implementation of the ban on the use of 57 to 110 mm mesh sizes for exploitation of kingfish is mandatory, which the mesh size of 146 mm and above seems to be appropriate for responsible fishery of the species. However, recommendation of standard mesh size needs to be re-examined in field trials
Assessment of water quality in the Wiśniówka River considering circulation of organic matter
Get PDFVariation of hydrochemical conditions, with special reference to adequacy of waters as fish habitats, was traced based on selected hydrochemical parameters obtained during the studies conducted from February 2013 till February 2014 year. The results were compared with earlier studies. The sources of organic pollution were identified, and the effects of biogenic substances on the biomass, as well as the self-purification capability of the river, were assessed. The total suspension exceeded the requirements for waters which are habitats of both salmonid and cyprinid fishes. Compared to the previous years, the load of organic and inorganic matter in the waters of Wiśniówka River increased; this may have resulted from external inflow, neighbourhood of the hatchery but also, to a small extent, from internal supply. The high availability of nitrogen-(NNH_4+; N-NO_2-, N-NO_3-) and phosphorus-(total phosphorus; P-PO_4 ^3-) based biogenic (substances favoured the biomass production, thus contributing to the increase in organic matter load in the river
Seafood industry: gender inequalities and the path forward
Get PDFA survey among seafood professionals, while revealing gender inequalities across the seafood industry in most countries, also provides pointers for positive change
Mexico: female fishers in Lake Chapala
Get PDFMeet Alejandra and Maria Elena, women fishers from Mexico’s Lake Chapala region, whose work contradicts the belief that fishing is something that only men can d