Disclaimer note - WWF - Pakistan

More documents

Recommendations

Info

Detailed Ecological Assessment Report 2008 – Keenjhar Lake Commonly called Blue crab, this species is undoubtedly the most abundant crab species of the Keti Bunder and suburbs. It prefers to live on sandy bottoms, in lagoon and bay. It hides in the sand when threatened. Large swimmer crabs, carapace with large lateral spines, a series of 8 small anterior spines (on each side of the eyes), spines along the claws. Blue color not always present on legs and claws tips. Carapace is usually 20 cm wide. A spine at distal end of posterior border of mercus of cheliped, front composed of four teeth. 3.7.3 Zooplankton at Keti Bunder Zooplanktons captured during sampling from Keti Bunder were found to belong to the sub-class Copepoda of the class Crustacea. Acartia is the numerically dominant species in the early spring to early summer faunal assemblage in the Keti Bunder area. Phylum Arthropoda Class Crustacea Subclass Copepoda Order Calanoida Family Acartiidae Genus: Acartia Dana, 1846 • Copepoda Copepods, cladocerans and other larval crustaceans make up the microcrustaceans. The free-living copepods, together with the parasitic copepods constitute the Order Copepoda of the Class Crustacea in the phylum Arthropoda. The copepods are the largest and most diversified group of crustaceans. At present they include over 14,000 species, a surely underestimated number, inhabiting marine and fresh waters, semi terrestrial habitats, or living in symbiotic relationships with other organisms. Copepods are an exceptionally important group of freshwater zooplankton. They utilize varieties of food items ranging from detritus; bacteria to a wide array of unicellular and multi-cellular phytoplankton and themselves serve as an excellent food for zooplanktivorous fish. Their nutritional value is higher as compared to that of Rotifera. These play vital role in energy transfer from primary producers to secondary consumers in aquatic ecosystem. Marine copepods are slightly larger than marine rotifers and smaller than newly hatched brine shrimp. 3.7.4 Impact on the ecosystem The invasion of Acartia tonsa into the Arabian Sea has a positive impact regarding its position as a fish food item. On the other hand, increase in its abundance is responsible for the stock decline of Calanipeda aquaedulcis. Similarity of habitat requirements of these two species has strained their competition. 3.7.5 Discussion It has been suggested that the zooplankton abundance allows for the enhanced survival and growth for fish larvae. The zooplankton biomass supports high ichthyoplankton concentrations. Many zooplanktons including the copepods are known to be the important component of the larval fish diets. Predaceous invertebrates preferably prey upon the smaller zooplankton. If the nutrient supply is not continued, the elevated predation by fish larvae also creates food limitation. The predation pressure therefore not only controls the abundance of the WWF Pakistan – Indus for All Programme Page 107 of 188
Detailed Ecological Assessment Report 2008 – Keenjhar Lake zooplankton but can also change the composition and size spectrum of zooplankton community. Zooplankton density and the gill infection of fish are inversely proportional to each other. At a low zooplankton density the fish fingerlings change their feeding behaviour and due to the insufficient zooplankton, they ingest a larger number of fish parasites from the detritus. It is possible that the lower intensity of gill infection at a high zooplankton density could also be explained by the more intensive fish parasite consumption by the copepods. Dodson and Frey (1991) and Williamson (1991) also include keys to identification. The keys for the copepods and cladocerans go only as far as the genus level. Since taxonomy is a dynamic science, names of some groups have changed with time; thus professionals also use a widely scattered primary literature. In Pakistan, however, no profound work has been done regarding the identification and keymaking of the zooplankton and there is dearth of literature which adds to the complications related to the identification of the rich and diverse zooplankton fauna of Pakistan up to the species and, in many cases, even up to the genus level. Zooplanktons are common in the pelagic and littoral regions of ponds, lakes, large rivers, and oceans. In freshwater, these assemblages are dominated by the rotifers and two groups of micro-crustaceans—the four orders of cladocerans and the class Copepoda. The copepods are also dominant in marine environments. The littoral and benthic regions of freshwater and marine environments characteristically hold large numbers of the diverse and ancient micro crustacean class Ostracoda. Most species of these four groups make their living grazing algae from the water column or off surfaces and are, in turn, a vital link for passing energy up the food chain to fish. Zooplanktons occupy an important position in the trophic structure and play a major role in the energy transfer of an aquatic ecosystem. An inadequate knowledge of the zooplankton and their dynamics is a major handicap for better understanding of life processes of fresh water bodies. Such studies have extreme significance and ecological value since eutrophication is bound with the components and production of zooplankton. Among zooplankton, the relative abundance of copepods was dominant in the Keti Bunder. The abundance of crustaceans collected by the plankton net method was found healthier than their usual abundance in polluted areas of the oceans. Detectable changes in the abundance or species composition of zooplankton may reflect fundamental changes in the aquatic environment affecting phytoplankton. In turn, because zooplankton are eaten by larger animals, some of which are of commercial importance, changes in zooplankton communities can provide early indications of forthcoming changes in the food conditions for fish, birds and mammals. As most of the zooplankton are relatively short-lived and have enormously high growth rates, they respond quickly to the environmental perturbations that influence diversity, such as any localized or broad-spectrum pollution, degradation and predation pressure. Crustacean zooplankton growth and development rates are well known to depend strongly on water temperature. The diversity in the stages of life history of the copepods may also be a sensitive early warning of temperature increases in the aquatic ecosystems in response to global atmospheric warming. WWF Pakistan – Indus for All Programme Page 108 of 188
Page 2 and 3:
Disclaimer note This information sh
Page 4 and 5:
Detailed Ecological Assessment Repo
Page 6 and 7:
Page 8 and 9:
List of tables Detailed Ecological
Page 10 and 11:
List of figures Detailed Ecological
Page 12 and 13:
Page 14 and 15:
Page 16 and 17:
Page 18 and 19:
Page 20 and 21:
Page 22 and 23:
Page 24 and 25:
Page 26 and 27:
Page 28 and 29:
Page 30 and 31:
Page 32 and 33:
Page 34 and 35:
Page 36 and 37:
Page 38 and 39:
Page 40 and 41:
Page 42 and 43:
Page 44 and 45:
Page 46 and 47:
Page 48 and 49:
Page 50 and 51:
Page 52 and 53:
Page 54 and 55:
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
Page 62 and 63:
Page 64 and 65:
Page 66 and 67:
Page 68 and 69:
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
Page 78 and 79: Detailed Ecological Assessment Repo
Page 88 and 89: 42 Leiognathus splendens Leiognathi
Page 90 and 91: 64 Rastrelliger kanagurta Scombrida
Page 112 and 113: Mukhtar, 1988 14 Narejo, 1996 Detai
Page 154 and 155: S. No. Detailed Ecological Assessme
Page 168 and 169: Index value 0.96 0.94 0.92 Detailed
Page 170 and 171: Comparison value 0.8 0.7 0.6 0.5 0.
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198 and 199:
Page 200 and 201:
Page 202 and 203:
Page 204 and 205:
Page 206 and 207:
Page 208 and 209:
show all

Disclaimer note - WWF - Pakistan

Create successful ePaper yourself

Delete template?

Save as template?