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The larvae of crustaceans, including those of brachyuran crabs, are a significant part of zooplanktonic communities constituting an ecologically important fraction of the pelagic communities. The present study describes taxonomic studies on three megalop stages of Portunus pelagicus (Linnaeus, 1758), Charybdis feriatus (Linnaeus, 1758) and Carcinus maenas (Linnaeus, 1758) belonging to family Portunidae collected from Indus deltaic creek system. Zooplankton samples were collected from three locations: Shahbandar 24°15’48.083’N, 67°90’15’333’E, Ketibandar 24°9’16.06’N, 67°27’7.64’E and Korangi creek 24°48’18.80’’N, 67°12’30.31’E during April to October 2018. No data available on taxonomic studies of portunid megalops upto species level from Paksitan, hence this is a first attempt to examine and to describe taxonomic features of megalops collected in the zooplankton samples. This study will contribute to the scientific knowledge on megalops taxonomy and identification as well as be useful for future research by taxonomists and biologists.

One of the essential factors to be addressed in the development of aquaculture is the feeding regime. This study was investigated to assess the effects of feeding rate on growth performance, feed utilization, chemical body composition survival rate, cannibalism and morphological indices of Asian Seabass, Lates calcarifer. Intended for the trial, one hundred forty sea bass individuals with an average weight 5.47 ± 0.11 g were randomly distributed in 4 concrete tanks (914 cm × 183 cm 122 cm) each; length × width × depth) and volume 18,399 L, for total 68 days. The fishes were fed with a pelleted diet containing 46% crude protein for different feeding groups designated as (T1, T2, T3 and T4). The feed was supplied with a rate of (T1) 3%, (T2) 4%, (T3) 6%, and (T4) 9% of fish biomass per day and feeding frequency were maintained three times per day to all the groups. At the end of the trial water physicochemical parameters was in acceptable range for Asian sea bass growth. The average daily weight gain (g), weight gain (g) and specific growth rate (%) was significantly higher (p

To estimate the growth parameters, the non-seasonal von Bertalanffy and Hoenig seasonal von Bertalanffy models were fitted to the length frequency data of Holothuria atra and H. arenicola obtained from coastal areas of Karachi in the northern Arabian Sea, Pakistan between January and December 2014. The Hoenig seasonal von Bertalanffy growth parameters were estimated as L∞=36.1 cm total length (TL), K=0.75 year-1 for H. atra and as L∞=34.9 cm TL, K=0.70 year-1 for H. arenicola. H. atra individuals reached 73.9% of their maximum total length at the one year old. For H. arenicola it was calculated as 72.7%. Monthly mean growth rate of H. atra at the same ages was calculated higher than H. arenicola. The seasonal oscillation in growth rate for H. atra (C=0.50) was larger than it was for H. arenicola (C=0.37). The time of the year when the growth is slowest corresponded to the middle of April (WP=0.30) in H. atra and at the beginning of August (WP=0.60) in H. arenicola may be the result of the extended both reproduction and poor nutrition periods due to monsoonal effects on the marine environment. The relatively high growth rates (K>0.7 year-1) of these two species may have important implications for high survival rate, particularly in environmental condition where cause biological stress and marine confusion but may also increase their potential as a candidate species for aquaculture.

In this study, muscle samples collected from Planiliza subviridis (Valenciennes, 1836) and Ellochelon vaigiensis (Quoy & Gaimard, 1825) caught on the Balochistan coast (Damb Harbor) between January and December 2015 (during the northeast monsoon, post-monsoon and pre-monsoon seasons, and the southwest monsoon) were analyzed to determine concentrations of heavy metals: iron, zinc, copper, manganese, cadmium and lead by an atomic absorption spectrophotometer, expressed per unit of dry weight of each sample. The average measured level of Fe, Zn, Cu, Mn, Cd and Pb for P. subviridis was 26.70 ± 11.49 μg g−1, 13.82 ± 4.56 μg g−1, 1.66 ± 0.84 μg g−1, 0.24 ± 0.10 μg g−1, 0.06 ± 0.07 μg g−1 and 0.17 ± 0.14 μg g−1, respectively. The average level of the same metals for E. vaigiensis was 29.26 ± 10.18 μg g−1, 18.85 ± 6.28 μg g−1, 2.18 ± 1.01 μg g−1, 0.32 ± 0.14 μg g−1, 0.25 ± 0.11 μg g−1 and 0.30 ± 0.12 μg g−1, respectively. The highest Pb accumulation (0.56 μg g−1 and 0.61 μg g−1) detected in P. subviridis and E. vaigiensis is above the limit value (0.50 μg g−1) reported by FAO, hence the accumulation of Pb in these two fish species should be monitored in the future.

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.

Salinity is one of the most critical environmental parameters regarding fish physiology, modifying food intake and growth performance in many fish species. The present study has investigated the effects of different salinity levels on growth performance, feeding and survival of Asian seabass Lates calcarifer juveniles. Asian seabass juveniles were reared at 0, 5, 22, 36, and 42 ppt salinity. One five hundred ninety-eight fish individuals with an average weight 1.2 ± 0.11 g were randomly distributed (166 fish/Tank) in 5 concrete tanks (30×6×4 feet) each; length × width × depth) and volume 19,122 L, for total forty days. Initially feeding rate of 6% biomass per day with 42% crude protein-containing diets daily. The feeding rate adjusted according to fish biomass every week. The results showed that salinity level had a significant effect on the weight gain, average daily weight gain, specific growth rate, feed conversion ratio, survival rate, total biomass and health indices (p < 0.05). The highest WG (39.11±1.49 g), ADWG, (1.00±0.12 g), SGR (8.74±0.03 % d-1) and lowest FCR (0.96±0.20) observed with T3 (22 ppt salinity) treatment, which was significantly higher compared to other treatment groups (p < 0.05). Among the health indices, the highest hepatosomatic index and viscerosomatic index found with 22 ppt salinity treatment, which was also significantly higher than the other treatment groups (p < 0.05). No significant differences were found among the treatments in terms of survival rate (p > 0.05), but the maximum survival rate (98.89±0.0 %) in T3 (22 ppt) and T2 (5 ppt). The maximum level of crude proteins (19.99±1.4%) was found in the whole-body biochemical composition (% of wet weight) of Asian sea bass juveniles in T3 treatment group reared at 22 ppt salinity. The second-order polynomial regression showed that 20 ppt salinity is optimum for the best growth of Asian sea bass. Thus, our present work would provide valuable information to the fish farmers for culturing the sea bass as well as its management along the inland and coastline of Pakistan.

The conventional taxonomy on sea cucumbers is challenging due to their morphological complexity. Molecular investigation of the class Holothuroidea was initiated for further clarity regarding the systematics and taxonomy of this class. A molecular phylogeny of the Holothuroidea was constructed by using maximum likelihood methods, and this unveiled variation in the existing taxonomic classification, which is largely based on the morphology of calcareous parts. H. pardalis and H. cinerascens from Pakistan was identified morphologically but no information was found with regard to molecular identification. This is the first research describing the molecular identification of H. pardalis and H. cinerascens based on 16S rRNA and COI genes from the Karachi Coast of Pakistan. Comparisons of mitochondrial 16S rRNA and COI to accessioned sea cucumber sequences on GenBank confirmed H.pardalis’ and H. cinerascens identity. This study is the first to report on molecular identification of H.pardalis and H. cinerascens based on the 16S rRNAand COI gene from the Karachi Coast, Pakistan.

To estimate the growth parameters, the non-seasonal von Bertalanffy and Hoenig seasonal von Bertalanffy models were fitted to the length frequency data of Holothuria pardalis and H. verucosa obtained from coastal areas of Karachi during January and December 2018. The Hoenig seasonal von Bertalanffy growth parameters were estimated as L∞ = 18.0 cm total length (TL), K = 1. 00 year-1 for H. pardalis and as L∞ = 18.0 cm TL, K = 0.86 year-1 for H. verrucosa. H. verrucosa individuals reached 68.9% of their maximum total length at the one year old class. For H. pardalis it was calculated as 54.2%. The seasonal oscillation in growth rate for H. pardalis (C = 0.90) was larger than it was for H. verrucosa (C = 0.18). The slowest period of growth corresponded to June in H. verrucosa and February in H. pardalis may be the result of the extended both reproduction and poor nutrition periods due to high rainfall regime. The relatively high growth rate (K) of these species may have important implications for their survival, mainly in environments where conditions cause biological stress and oceanic disturbances but may also increase its potential as a candidate for aquaculture.

In this review, the chemicals, some of the most important of which are heavy metals and their accumulation level in Mackerels, Tunas, and Bonitos in mainly the Arabian Sea and coastland in other seas were reviewed and compared.

An experiment of a-sexual reproduction by fission was conducted on sea cucumber, Holothuria (Lessonothuria) verrucosa (Selenka, 1867) for 98 days. Anterior fission was observed on Day 1 with the formation of fission on the body of the sea cucumber. Initial length of 14 cm and weight of 21 g was measured at Day 1 in an aquarium under laboratory condition. Complete fission was observed on Day 7 of experiment by formation of 2 specimens; A and P. Initial length and weight for A was 4.5 cm and 3.18 g, while P was 9.5 cm and 17.30 g respectively. Increased weight for specimen A was observed on Day 20 with the first observation of the formation of anal pore. Tentacles started to form on specimen P on Day 34. Complete formation of anus on specimen A was seen on the 98th day of experiment with final weight of 3.84 g and length of 4.6 cm. Large growth of tentacle was also seen on Day 98 of the experiment with a final weight of the specimen P as 17.56 g and length as 9.7 cm.

A preliminary study was conducted on the occurrence and abundance of zooplankton in the Karachi backwaters. Zooplankton sampling was conducted on monthly basis and the study was carried out on the basis of three seasons including pre-monsoon (January to May), monsoon (June to September) and post-monsoon (October to December) from a permanent station Napier Mole bridge (24 o 50’34’’.90 N, 66 o 59’17’’.55 E) during June 1996 to May 1998. The hydrographic parameters including air temperature ( o C), water temperature ( o C), salinity (ppt), dissolved oxygen (mg/L), pH, and transparency (cm) were recorded. Total 14 groups of zooplankton were recorded; hydromedusae, copepoda, mysids, amphipoda, acetes, lucifer, chaetognath, penaeid pl, caridean pl, zoea, megalopa, squilla larvae, fish larvae, fish eggs and others. Pre-monsoon season shows highest number of individuals and copepods were found to be the dominant group in all seasons. Zooplankton diversity, equitability and margalef index were measured seasonally. Highest shannon – wiener diversity index H' = (1.83), equitability E= (0.69) and margalef species richness Index d= (1.37) were measured in post-monsoon season. Statistical analysis (ANOVA) was performed in between seasons and zooplanktonic groups. No significant difference (at P>0.05, 0.148) was observed between zooplankton and seasons.

Concentrations of heavy metals Cd, Fe, Pb, Cu, Zn, Ni, Co, Cr and Mn in muscles, liver, kidney and gills of marine and native commercial fish of Chacunda gizzard shad Anodontostoma chacunda collected from Karachi fish harbour were determined to conduct a health risk assessment for people by the Atomic Absorption Spectrophotometer. The obtained results were expressed mg/kg dry weight. Results showed that Fe and Zn concentrations were the most abundant among all tissues whereas Cd and Pb levels were the lowest. The data obtained in this study were compared with the international maximum permissible values. The estimated values of all metals in muscles of fish in this study were below the permissible limits. Generally, risk values for the measured metals do not pose unacceptable risks at mean ingestion rate for edible tissues. It can be concluded that the heavy metal levels in edible parts of A. chacunda have no hazards for consumers

Objective: To determine heavy metal concentrations in holothurians (Holothuria arenicola, Holothuria pardalis, Holothuria verrucosa, Holothuria atra, Ohshimella ehrenbergii, Holothuria cinerascens, Stolus buccalis and Holothuria leucospilota), sediments and sea water samples from both Buleji and Sunehri coasts bordering Northern Arabian Sea during January to December 2014 and to assess the level of bioaccumulation using bioaccumulation factors. Methods: Fe, Mn, Zn, Cu, Cd and Pb levels were determined by Perkin Elmer AAnalyst 700 Atomic Absorption Spectrophotometer. Biota concentration factor (BCF) and biota sediment accumulation factor (BSAF) were also calculated. Results: The mean concentrations of heavy metals in body wall of sea cucumber ranged from 0.11 to 2.67, 0.43 to 8.93, 14 to 73, 0.76 to 7.12, 0.52 to 3.02 and 11 to 46 µg/g dry wright for Cd, Cu, Fe, Mn, Pb and Zn, respectively. The greatest biota-sediment bioaccumulation factor (BSAF) value for Zn (3.29) was observed in H. leucospilota at Buleji during pre-monsoon, indicating the species as microconcentrator. The BSAF values for Cd in sea cucumber ranged from 0.042 to 1.492. Conclusions: The results suggested that the studied sea cucumber species ranged from being microconcentrators to deconcentrators. The BSAF values of Cu, Fe, Mn and Pb were low, indicating the species as deconcentrators. Zn in all species from Sunehri coast is “very bioaccumulative” (BCF > 5 000) during all sampling periods. Cu, Fe, Mn and Pb can be considered “bioaccumulative” (BCF < 5 000).

In this study the amounts of mercury (Hg) were determined in tentacles and muscle tissues of O. ehrenbergii and S. buccalis from two coastal sites of Karachi; Buleji and Sunehri during Southwest monsoon (August and September) and Northeast monsoon (December and January) seasons of the year 2018. The mean amounts of Hg in edible tissues of sea cucumbers were as follows: O. ehrenbergii (0.0176 mg/kg dry wt.) and S. buccalis (0.0155 mg/kg dry wt.). Hg amounts in muscles of both species are much lower than the maximum permissible limits (0.5 mg/kg wet wt.). Estimated Daily Intakes for adults consuming O. ehrenbergii and S. buccalis are lower than published RfD values. Total Target Hazard Quotient (TTHQ) values (0.00787) are also lower than 1, it may be concluded that the consumption of these sea cucumbers from Karachi, do not pose any health hazards to human as Hg amounts were concerned. Higher Education Commission of Pakistan

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.

In the present study, Scomberomorus commerson was collected during the period 2006-2011 in order to pro- vide information on the concentrations of eight heavy metals present in this marine species commonly consumed by the population and to have knowledge whether these levels may constitute a hazard to consumers. Liver showed high concen- trations of metals in the tissues and organs. Fe is the most accumulated in all tissues and organs. The highest mean con- centration of Fe (608.93+113.22 µg/g), Mn (9.79+4.22 µg/g), Cu (38.57+16.62 µg/g), Zn (53.25+26.50 µg/g), Ni (3.22+1.13 µg/g), Pb (1.20+0.64 µg/g), Cd (2.03+0.91 µg/g) and Cr (1.93 + 0.87 µg/g) was determined in liver of fish. The order of abundance of the metals in the fish samples based on concentrations in the muscle tissues analysed were as follows: Fe>Zn>Cu>Mn>Ni>Cd>Pb≥Cr. For the toxic metal, Pb was found to have lower concentration of the mean val- ues than the permissible limits set by FAO/WHO. However, Cd level was higher than the permissible limit and it can be concluded that the contamination of Cd in S. commerson may pose threat for the importers due to high per capita con- sumption of the fish.

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 . a renicola , 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.