Aspects of Population Dynamics of Tiger Tooth Croaker, Otolithes ruber (Bloch and Schneider, 1801) from Northwest Arabian Gulf, Iraq

The present study consists of the growth, mortality, relative yield recruit and virtual population analysis of tigertooth croaker, Otolithes ruber from Iraqi marine waters, northwest Arabian Gulf between February 2020 and January 2021. Analysis of population dynamics employed methods fitted in FiSAT II software using pooled length-frequencies. A total of 3835 individuals of O. ruber ranged from 17.0 to 60.0 cm have been collected. The exponent (b) of the length-weight relationship was found to be 2.755. The von Bertalanffy growth parameters (L∞ and K) were estimated as 68.5 cm and 0.36, respectively, while the growth performance index (Ø') was 3.228. The total mortality (Z) was calculated as 1.10, while the natural and fishing mortality rates were 0.69 and 0.41, respectively, and the current exploitation rate (Ecurrent) was 0.38. Fish were recruited to the fishery at a mean size of L50= 20.55 cm. The recruitment pattern of O. ruber was continuous throughout the year with two major peaks. The analysis of yield-per-recruit (Y/R’) indicates that the current exploitation rate was below the biological target reference points (E0.1 = 0.40 and Emax= 0.53), refer to the stock of O. ruber is underexploited. The 27 cm length group was more vulnerable to fishing and more harvested according to virtual population analysis. sLength at first capture was higher than the length at first maturity of the species in the region. For management purposes, more yields could be obtained by increasing the mesh sizes of the nets employed in the fishing of the species.

Stock assessment of the Tigertooth croaker, Otolithes ruber (Bloch & Schneider, 1801) from the commercial prawn trawl fishery by-catch in coastal Kenya

Commercial bottom prawn trawling has been reported to generate a higher proportion of by-catch of up to 70% in Kenya. The Tigertooth croaker, Otolithes ruber is one of the species caught in large quantities as commercial by-catch and also by artisanal fishers. This has led to growing concern that the species could be at risk of over-exploitation. The purpose of this study was to carry out a stock assessment of O. ruber. Stock assessment parameters were estimated using ELEFAN with the generic algorithm as included in the R package TropFishR. The length-converted catch curve and the length-based yield per recruit model were employed. The exploitation rate (F/Z = 0.71) indicates that the stock is overfished based on the length-converted catch curve. The current fishing mortality (F = 2.3) based on the catch curve is larger than the reference level ( = 1.1) based on the yield per recruit analysis and also indicates that the stock is overfished (= 2.09). To reverse the current trend of exploitation, improved management of the stock is required, which should include further studies on other by-catch species and the generation of data to capture the whole fishery for a better estimation of stock status.

Reproductive Biological Performance of Otolithes ruber (Bloch and Schneider 1801) in San Miguel Bay, Philippines

The tigertooth croaker, Otolithes ruber (Bloch and Schneider 1801), was studied to determine its reproductive biology characteristics for 34 months from March 2015 to November 2017. A total of 7,977 individuals were sampled and the measured total lengths (TL) ranged from 8.1 cm to 32.1 cm (16.70 ± 2.53 cm ) and 10.0 cm to 33.5 cm (17.95 ± 2.95 cm) for male and female, respectively. The length-weight relationship can be summarized as W = 0.00521 L3.18 and W = 0.00837 L3.01 for female and male, respectively. The length at first maturity of this species was determined to be 13.95 cm, which is smaller compared to other studies. The overall sex ratio of this species was 1:0.8, with males dominating the female sex (P < 0.05, X2 = 64.3). In addition, synchronized development of male and female gonads was observed. It was also verified that mature individuals were present all throughout the study period indicating that this species spawn continuously and the presence of juveniles during the sampling period indicated continuous recruitment. Mean monthly GSIs indicate July to November as the main spawning season of this species. The in-site occurrence of mature and juvenile stocks in the bay further implicates that San Miguel Bay is a nursery ground for this species. The fecundity varied between 3,420 to 422,100 with an average fecundity of 86,142 eggs. Lastly, the spawning potential ratio is still above the limit reference point (SPR = 0.36), indicating that the stock can still replenish their biomass.

Identification and authentication of commercial mi-iuy croaker (Miichthys miiuy) products by two PCR-based methods

Mi-iuy croaker (Miichthys miiuy) is one of the most important ingredients of Korean cuisine and thus has the highest economic value. However, the similar morphological traits among croaker fish belonging to family Sciaenidae are often exploited for seafood fraud. In this study, M. miiuy-specific primer set was designed and further improved by the development of a rapid and cost-effective duplex PCR method. The specificity of M. miiuy-specific duplex PCR was tested using 22 seafood species, and no cross-reactivity was observed. The sensitivity of the PCR assay was found to be 0.1 ng/µL. For the first time, labeling compliance of 43 commercial m-iuy croaker products was verified using both full DNA barcoding and M. miiuy-specific duplex PCR methods. For species identification, BOLDSYSTEMS and GenBank database were screened with the consensus sequences of each PCR product as a query. This identification result was further confirmed using the M. miiuy-specific duplex PCR method. The findings of this study revealed that principal species substituted were law croaker (Pseudotolithus senegallus, n=4), bigeye croaker (Micropogonias megalops, n=3), whitemouth croaker (Micropogonias furnieri, n=1), and tigertoothed croaker (Otolithes ruber, n=1). A significant percentage (21%) of mislabeling was present in commercial mi-iuy products sold on the South Korea market.

Stock identification of tiger tooth croaker Otolithes ruber (Schneider, 1801) along the Indian coast using truss network analysis

The tiger toothed croaker Otolithes ruber (Schneider, 1801) of the family Sciaenidae is a demersal fish that contributes significantly to the marine landings of India. To identify stock units of O. ruber based on body shape morphometry, truss network analysis was carried out based on specimens collected from four selected locations, two each from east coast (Digha and Chennai along Bay of Bengal) and the west coast (Cochin and Ratnagiri along Arabian Sea) of India. A total of 20 truss distances along the fish surface, including head, mid body and posterior region were measured and transformed measurements were subjected to factor analysis and discriminant function analysis. The bivariate plot score of factor analysis indicating two distinct stocks on both the coasts may be the consequence of geographical isolation and different environmental conditions along the Bay of Bengal (east coast) and Arabian Sea (west coast). The Ratnagiri and Cochin population showed considerable mixing which indicated the presence of a unit stock along the west coast. However, existence of strong morphometric differentiation between Digha and Chennai populations indicated two separate spawning populations in the Bay of Bengal. In the cross-validation of Discriminant function analysis, the most well classified group was Digha population (97.85%). The present study suggests the possible existence of three stocks of O. ruber, one in west coast (Cochin and Ratnagiri) and two in east coast (Digha and Chennai) which can be considered while formulating effective management strategies for the species.

Heavy metals analysis in some freshwater and marine fish species from markets of Lahore, Pakistan

Muscle portion of 72 fish samples of eight selected species, four from marine (Pampus Chinensis, Otolithes ruber, Trachipteridae and Oncorhynchus tshawytscha) and four from fresh water (Labeo rohita, Catla catla, Rita rita and Walago atu) fishes were collected from three superstores in Lahore, Pakistan. The prepared fish samples were analyzed for determination of Chromium (Cr), Lead (Pb) and Cadmium (Cd) concentrations by using the inductively coupled plasma (PerkinElmer, Model: Optima 7000DV ICP-OES). It was found that Cd (0.294±0.001 mg/kg) concentration was the highest in Labeo rohita collected from Metro Superstore while the lowest level (0.023±0.000 mg/kg) was in the Oncorhynchus tshawytscha of the same superstore. Species wise concentration of Cd varies significantly. Concentration of Cr (0.172±0.001mg/kg) was the highest in Oncorhynchus tshawytscha collected from Main Fish Market of Lahore while the lowest level (0.002±0.001mg/kg) was in Labeo rohita collected from Hyperstar superstore. Concentration of Pb (0.057±0.000mg/kg) was the highest in Oncorhynchus tshawytscha collected from Metro Superstore while the lowest (0.012±0.001mg/kg) in Otolithes ruber of the same superstore. Species wise concentration of Pb varies non-significantly. Origin wise t-test shows that: a) Cd concentrations vary significantly, while Cr and Pb concentrations vary non-significantly when marine and fresh water species were compared. b) The range of Pb (0.011-0.057 mg/kg) and Cr (0.002-0.172 mg/kg) was within limits and of Cd (0.023-0.297 mg/kg) was higher than the WHO international standards (0.123 mg/kg for Pb, 0.050 mg/kg for Cd and 0.1 mg/kg for Cr) in most of the fish species of main Fish Market Lahore, Hyperstar and Metro store.