View Crossmark dataFrontiers in Life Science, 2015 Vol. 8, No. 1, 71-96, http://dx.doi.org/10.1080/21553769.2014 The fishery, biology, growth and stock structure of Euthynnus affinis is studied in detail. Hooks and lines, gillnets and purse seines are the major equipment used to exploit the fish. Fisheries are sustained mainly by 1-2 year old fishes (34-50 cm). Spawning was observed around the year with peaks during July-August and November-January. The length-weight relationship is 0.0254 L2.889 with no significant difference between males and females. Age and growth are estimated using length based methods. The maximum sustainable yield estimated was higher than the average annual catch, indicating scope for further exploitation. Elevated levels of heavy metals in Euthynnus affinis may be a good indication of pollution of an aquatic ecosystem due to anthropogenic influences. A total of 278 fishes were collected from Karachi coast, Fish Harbor West Wharf, Karachi, for metal (Cd, Pb, Zn and Cu) analysis in the organs of the fish. The metal levels in the sample fishes are in descending order of toxicity Cd > Pb > Zn > Cu. In the risk assessment, we assessed potential human health risks associated with consumption of fish, incorporating information gathered during a year-long, intercept-style creel angler survey and representative heavy metal concentrations in fish tissue. Fishing operations can cause ecological impacts of different types, e.g. by the catches, damage of the habitat, mortalities caused by lost or discarded gear, pollution, and generation of marine debris. Periodic reassessment of the tuna potential is required, with adequate inputs from exploratory surveys as well as commercial landings; this may prevent any unsustainable trends in the development of the tuna fishing industry in the Arabian Sea.

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Abstract. Yousif RA, Choudhary MI, Ahmed S, Ahmed Q. 2020. Review: Bioaccumulation of heavy metals in fish and other aquatic organisms from Karachi Coast, Pakistan. Nusantara Bioscience 13: 74-85. Heavy metals are being utilized in a variety of ways in industries, agriculture, food processing and household in many forms. Metals are unique environmental and industrial pollutants in the sense that they are neither created nor destroyed by human beings but are only transported and transformed into various products. The present study deals with the findings of various investigators on the effect of heavy metals on fish and other aquatic organisms on Karachi coasts of Pakistan. The polluted areas (Rivers and Karachi coasts) receiving effluents from industrial, agricultural, municipal and domestic wastes. The order of abundance of the metals were as fellow; Fe > Zn > Cu > Mn > Cd > Pb > Cr > Ni > Hg > As. Most studies showed that essential metals (Fe, Zn, Cu, and Mn) in aquatic organisms are much high, but the quantities of non-essential metals are found to be less. This review has shown that fish and other aquatic organisms are used as bio-monitoring species in heavy metal pollution. It is suggested that such investigations should be continuous in terms of both human health and determination of metal pollution in aquatic environment.

Length-weight relationships and condition assessment are a common practice in fisheries analyses; however, such information is unknown for most sea cucumber species. The present study investigated length-weight relationships and relative condition indices of four commercially important sea cucumbers: Holothuria arenicola, Holothuria atra, Holothuria pardalis and Holothuria verrucosa. Additionally, the seasonal variations obtained between three climatic seasons (pre-monsoon, monsoon and post-monsoon) were analyzed. The results showed that the four species grow allometrically, with negative allometric b values ranging from 0.84 to 1.74. There were significant differences of length-weight relationships between climatic seasons for H. arenicola and H. atra. The lower b values were observed during post-monsoon and the higher b values during monsoon in three of the four species. During the post-monsoon, the condition of the bigger individuals of H. arenicola and H. atra was lower than that of the small individuals. The differences in length-weight relationships of H. pardalis and H. verrucosa were not significant between climatic events. The higher temperatures occurred during monsoon and the lower during post-monsoon, but these data only showed a significant correlation with the relative condition factor of H. arenicola. Best condition of the individuals of H. arenicola occurred at temperatures between 22 to 31°C. Studies about environmental variables and characteristics of the substratum type are necessary in order to complement the understanding of the length-weight relationships and condition of these species.

The present study was conducted to investigate the contamination of Fe, Mn, Cu, Zn, Ni, Pb, Cd, and Cr in the tissues of commercially important fish Thunnus tonggol and to evaluate risks to human health associated with seafood consumption. The results from this study showed that the concentrations of all metals measured except Cr were relatively high in the liver compared to the muscle, gills and gonads. High concentrations of Cr were present in the kidneys. Fe had the highest concentration compared with other metals tested in all tissues of followed by Cu and Zn. the present study revealed that all metals except Cu and Cd concentrations in the muscle tissues were lower than the maximum permissible limit as recommended by the international regulations. However, the estimated the Provisional Tolerable Weekly Intake (PTWI) of Cu is below the established PTWI. The data indicate that the examined fish were polluted with Cd. It was also found that levels of the metals in other tissues in some samples were higher than the recommended concentrations. However, consumers do not consume the liver, kidney, gills and gonads.

Two specimens of a species herein identified as Holothuria (Lessonothuria) insignis Ludwig, 1875 and a single specimen identified as Holothuria (Lessonothuria) lineata Ludwig, 1875, were collected from the intertidal zone at low tide from two coastal localities in Karachi (Buleji and Sunahri). This paper briefly documents their morphology and habitat characteristics and formally resurrects H. (L.) insignis from the synonymy of H. (L.) pardalis Selenka, 1867, based on the observations of the ossicles assemblage deduced from current material, syntype, some material at the NHMUK (Natural History Museum,UK), and literature. H. pardalis is also commented on and compared with its related congeners in Pakistan, in tabular form. A key is presented of all species of the Lessonothuria group currently recognized in WoRMS.

Nowadays metal bioaccumulation in holothuroids is increasing and is a cause of worry owing to toxicity. In the present study the concentrations of mercury (Hg) were measured in holothuroids (Holothuria (Thymiosycia) arenicola Semper, 1868, Holothuria (Lessonothuria) pardalis Selenka, 1867, Holothuria (Lessonothuria) verrucosa Selenka, 1867 and Holothuria (Halodeima) atra Jaeger, 1833) collected during different seasons (pre-monsoon, monsoon, and post-monsoon) in 2015 at Buleji and Sunehri coasts of Karachi, Pakistan. Hg concentrations of tentacles were higher than those in muscle, tentacle and gut tissues of the pre-monsoon, monsoon and post-monsoon. The lowest Hg concentrations were found in muscle tissues at all seasons in Buleji and Sunehri coasts. The mean levels in the muscle tissues were 0.018 mg/kg dry wt. for H. arenicola, 0.024 mg/kg dry wt. for H. verrucosa, 0.026 mg/kg dry wt. for H. pardalis and 0.036 mg/kg dry wt. for H. Atra. The results indicate that according to the European Union legislation the Hg amounts in all tissues of holothurians is much lower than permitted levels. In terms of Estimated Weekly Intakes, this current work also proved that there was no likely health hazard to consumers on account of intake of sea cucumbers under the current consumption rate in Buleji and Sunehri coasts of Karachi, Arabian Sea.

Plastic material dominates our life and accordingly, it dominates the environment as a pollutant. Pakistan coasts are facing with plastic pollution problem like the rest of the world. The number and types of microplastics found in sea water and sediment samples from 25 locations along the Arabian Sea coast of Pakistan were explored in this study. The results of the present study show that the region is under a high pollution from microplastics. Microplastic abundance in seawater was found as mean 582.12±246.14 particle. L-1 and in sediment samples was mean 987.40±617.06 particle.kg-1 dry sediment. Microplastic concentration was maximum in Manora both seawater and sediment samples. Fibers were major contribution to total microplastics, up to 99% of all samples both seawater and sediment samples.