The Role of Fecal Pellets in the Flux of Carbon to the Sea Floor on a River-Influenced Continental Shelf Subject to Hypoxia.

The Louisiana continental shelf near the Mississippi and Atchfalaya River deltas is a stratified and highly productive coastal system characterized by the largest hypoxic (dissolved oxygen $\u3c$2 mg l\sp{-1}) zone in the western Atlantic Ocean. Carbon export from surface waters in the form of sedimenting zooplankton fecal pellets was examined to determine its importance in the formation and maintenance of oxygen deficiency in the bottom waters. Two sediment traps (5-6 and 15 m) were deployed in 1991 and 1992 in 20 m water depth within an area of chronic and seasonally severe hypoxia. I determined the fecal pellet number and carbon flux, and total carbon flux from the surface waters, the percent primary production exported as fecal pellets, and the potential for fluxed fecal pellet carbon to support bottom water hypoxia. I also quantitatively sampled the water column at discrete depths for fecal pellets and zooplankton to determine potential source organisms and their seasonal, diel and spatial variation. The highest densities of total organisms, copepods and copepod nauplii occurred during March and April (1992), when chlorophyll a concentrations in surface waters were highest, and decreased in summer and fall. The abundance of fecal pellets was positively correlated with total organisms, copepods and copepod nauplii, the likely source of fecal pellets. The fluxes of total particulate material, organic carbon, organic nitrogen, fecal pellet carbon and phytoplankton carbon varied similarly between seasons, and was lowest in summer and highest in spring. The fluxes were greater in 1991 than in 1992. Seasonal variations in fecal pellet number and carbon flux were positively correlated with indicators of high surface water productivity in 1991, but not in 1992. The flux of fecal pellets from surface to bottom waters accounted for 55% of the particulate material exported vertically, exceeded phytoplankton carbon fluxes, and was high enough to deplete the bottom water oxygen reserves in spring. The results support the hypothesis that the development of summer hypoxia is associated with the decomposition of organic matter accumulated in spring primarily by the sedimentation of a phytoplankton bloom via fecal pellets, and not as intact phytoplankton cells

Allometric growth pattern, sexual dimorphism and size at the onset of sexual maturity in Opusia indica (Brachyura: Ocypodoidea: Camptandriidae) from mangrove areas of Pakistan

Size at sexual maturity and patterns of somatic growth are important aspects of reproductive history of crab. The main purpose of this study is to provide an estimate for the onset of morphological sexual maturity in mangrove crab, Opusia indica from a population located in Korangi creek intertidal mud flat (Karachi, Pakistan) based on relative growth. The crabs were monthly collected through quadrat method from March 2001 to February 2002. A total of 1702 crabs was obtained, of which 764 were males, 939 were female. The morphometric measurement of carapace, abdomen, cheliped and male gonopod was related to carapace width. Based on carapace width males were significantly larger than female, indicating sexual dimorphism. The size at onset of sexual maturity in males was estimated as 5.51 mm carapace width and 5.3 mm carapace width in females. The positive allometric growth of female abdominal width were likely related to the incubation process

Construction of earthen structure as a sexual signals in the fiddler crabs

We studied the reproductive behavior and the construction of an earthen structure in the four species of fiddler crab with reference to their habitat. Males of the Uca sindensis and U. iranica inhibit on open mudflats, construct the pillar and semidome structures at or near to the burrows openings. These structures perform the function to attract females, who wandering on the surface between male burrows for mating as well as provide protection or hiding object against the avian predator to mates. There were no earthen structures were observed in U. urvillie and U. annulipes, which inhibit among the vegetation. The well-marked intersexual different arrangement of mudballs was observed in U. annulipes. The earthen structures (pillar and semidome) and mudballs arrangements help courting females to assess the quality of mate as well as internal conditions of the burrow

Diversity and distribution of mangrove crabs in three intertidal areas of Balochistan, Pakistan

The mangrove crab diversity and densities were studied by transect analyses from three coastal sites (Bhaira, Dam and Miani) of Balochistan. Among all the macrofauna inhabiting in the mangrove swamps, some brachyuran crab species are among the most important taxa with regard to species diversity and distribution The brachyuran crabs were collected from the low tide level to high tide level. Diversity and distribution of crabs were significantly different between the sites and among tidal levels. A total of 14 species of brachyuran crabs was recorded belongs to the family Ocypodidae, Macrophthalmidae, Dotillidae, Camptandriidae, Grapsidae and Xanthidae. The 11 species were from the Bhaira mangroves, while 10 species were recorded in Miani mangroves. The abundance of crabs varied between the tide levels among three habitats

Tidal induced variation in the distribution, abundance and diversity of mesozooplankton along the Karachi coast, Pakistan

Temporal variations in biomass, abundance, diversity and species composition of mesozooplankton in relation to the tidal state were studied. Mesozooplankton sampling was carried out twice at the ebb and flood tides at fixed stations closed to Phitti creek (P) and Manora channel (M) near the Karachi coast during February 1999. The average percent abundance of mesozooplankton was high at ebb tide i.e., 66% and 63% whereas, low on flood tide i.e.,34% and 37%, at both stations respectively. However, there were no differences in species composition with tidal fluctuations at both sites. The mesozooplankton community was typically composed of 22 groups, out of which copepod was the most abundant group (comprising % of the total zooplankton) at both sites. During the flood tide high diversity 0.11 ± 0.021 was observed in Phitti creek, but no difference was observed at Manora channel. The species richness was high (2.30 ± 0.01273 and 2.38 ± 0.502) in the Manora channel at both ebb and flood tides, respectively, whereas the dominance values were high at Phitti creek. Complete randomized design ANOVA showed that there was no significant difference in abundance of mesozooplankton between stations and tides nested in stations, but the difference was significant for the diversity and equitability. On the short temporal scale the tidal cycle additionally determines changes in the zooplankton composition

Effect of similar feeding regime on growth and body composition of Indian major carps (Catla catla, Cirrhinus mrigala and Labeo rohita) under mono and polyculture

Growth performance and body composition of yearling Indian major carps (Catla catla, Cirrhinus mrigala and Labeo rohita) was evaluated in semi-intensive (mono and polyculture) systems for 90 days. Prior to stocking, all ponds were fertilized with organic and inorganic manures. This application was repeated every two weeks throughout the study period. Supplementary feed containing 35% protein was applied daily at 3% of wet body weight. In trial 1, all the three species gained significantly higher weights with experimental feed (F1) versus control group (F0). There was non-significant difference observed among species. In trial 2, non-significant difference was observed for net weight gain among species and between feeds. The feed conversion ratio (FCR), protein efficiency ratio (PER), protein utilization (PU), gross nitrogen retention efficiency (GNRE%) and gross energy retention efficiency (GERE%) were found non-significantly different among species in both trials, except GNRE% in polyculture, where L. rohita showed significantly higher values than its counterparts. No significant difference was observed in body composition and mineral contents among species and between feeds in both trials. In conclusion, all the three fish species performed well under monoculture system with 35% protein diet and showed significantly higher growth than the control, compared to polyculture, without any significant effect on body composition.Keywords: Artificial feed, Indian major carps, growth, proximate composition, nutrient retention efficiency, cost effectivenes

Feeding Diversity of Finfish in Different Wild Habitat

Sonmiani Bay has unique faunal diversity and distribution especially finfish as mangroves provides an imperative ecosystem which offer the shelter and protection to the associated organisms and care of their juveniles in bay limits. This study aimed to evaluate the diversity pattern according to physical and physiological responses and feeding habits (carnivorous and herbivorous) of finfish species in accordance with current habitat conditions in the Sonmiani Bay. A total of 4499, individuals of comprising 155 finfish species that represent 50 families were captured by these four (beach seines, purse seines, gill nets, and cast nets) nets during a twelve-month survey in a year. The distribution pattern of finfishes captured classified into four groups (tidal visitors, permanent residents, partial residents, and seasonal visitors) according to their patterns of distribution. Understanding of the true feeding behavior of organisms needs a more reliable and functional approach. The feeding ecology is not only functional for food and feeding behavior of fish as usually described by various tools and techniques of analytical research to take up more reliable details to explain the feeding biology in fish but also the indicator of habitat quality and status

Zonal Distribution and Population Biology of Ilyoplax frater (Brachyura: Ocypodoidea: Dotillidae) in a Coastal Mudflat of Pakistan

Zonal distribution and population biology of Ilyoplax frater were studied in a mangrove mudflat area of Pakistan. The crabs were collected from Korangi creek through transect and quadrat method from low tide level to high tide level. Two transects were delimited in a mangrove area of Korangi creek (24o79’N/ 67o20’E). On each transect, three 0.25 m quadrats were sampled at three tidal levels on a monthly basis during low tide periods from March 2001 to February 2002. A total of 1124 crabs were obtained, of which 482 were males and 642 were females. Density of crabs varied between 0 and 90 /m2. The density and size distribution varied and showed significant differences from low to high tide level, and were positively correlated with the percent moisture, percent organic matter and sediment grain size. The carapace width (CW) ranged from 2.5 to 11.5 mm for male and 2.5 to 11.0 mm for female and was not significantly different. The overall sex ratio did not differ significantly from the expected 1:1 throughout the year in small crabs but was significantly different in adult crabs (c2 = 49.73) with more male crabs. Size frequency distribution showed recruitment of juvenile crabs (< 4 mm) nearly throughout the year except during June and July. Presence of ovigerous females in all months with seasonal peaks in September, October, December and May indicates seasonal continuous breeding. Weight of egg mass increases with weight of ovigerous females and show positive linear relationship. The estimated mean diameter of egg was 2.83+ 0.25 mm, and the average number of eggs was 3065+ 902 [Current Zoology 56(2): 244–251, 2010]

Temporal and spatial variations in the species composition, distribution, and abundance of Copepods in mangrove creek area along the Karachi coast, Pakistan

61-69Among different groups of zooplankton collected from Korangi-Phitti mangrove creek area, copepods contributed maximum numerical abundance up to 68% and 75% at S1 and S2, respectively. Twenty one species of copepod, pertaining to fourteen genera and thirteen families were identified from the sample, Difference in diversity of copepod species among seasons with highest density in post monsoon at both stations was recorded. Acrocalanus longicornis, Paracalanus sp., Acartia sp., Temora sp., Oncea sp. and Coryceaus sp. were observed as the dominant and abundantly found copepod species throughout the study period. The highest diversity and equitability was observed in pre monsoon at both stations followed by north east monsoon and south west monsoon. Biomass and species diversity are in inverse relationship