Zooplankton diversity in Philippine Lakes

Sustainable fisheries development partly depends on the availability of adequate zooplankton as principal food items of early life history stages of economically important fish species as well as of the adults of some species such as clupeids (e.g., Sardinella tawilis of Lake Taal in Batangas). The broad characteristics of the composition of freshwater zooplankton (Rotifera, Cladocera and Copepoda) of natural and man-made lakes in the Philippines are compared with those of the Oriental Region, in particular, and other tropical regions, in general. Two species of calanoid copepods are endemic, a somewhat remarkable occurrence considering that calanoids are represented by only five known species in the Philippines and absent in many large tropical lakes. Daphnia, which almost invariably influences food-web interactions and structures of plankton communities in temperate lakes, still has to be recorded

Translocation of the clupeid Sardinella tawilis to another lake in the Philippines: A proposal and ecological considerations

The dwindling commercial catch of Sardinella tawilis (Clupeidae), locally known as 'tawilis', reported in recent years by local fisher folk in Lake Taal, Batangas, Philippines, could be a result of the interaction of factors such as over fishing, destructive fish-capture techniques, changes in water quality, and others. Like the rest of the handful of endemic freshwater fish species in the Philippines, S. tawilis is threatened with depletion of its stocks, if not with extinction in the near future. A conservation strategy that could be considered is the translocation of 'tawilis' to another lake in the Philippines, whose ecological features closely resemble those of Lake Taal and where 'tawilis' would receive socio-economic and cultural acceptability. Cases of clupeid introductions - natural and man-made, successes and failures - are presented from published literature. Special attention is given to the case of a well-planned trans-country (Thailand-to-Indonesia) attempt to introduce a clupeid fish. The broader questions of biodiversity, endemicity, conservation, and fish community structure in Lake Taal (and elsewhere) must be underpinned by sound basic taxonomy and ecology

Autoecology of an endemic calanoid copepod: The first step in biodiversity conservation in Lakes

Abstract only.Copepods, specifically calanoid copepods, play an important role in the productivity of aquatic ecosystems since they serve as a crucial link between primary producers and carnivores. In tropical reservoirs and lakes, they are not only a major source of food for many invertebrates and zooplanktivorous fish, but also good biological indicators. Calanoid/cyclopoid-cladoceran ratio is used in limnological studies as an indicator of water quality. In the past, studies in the Philippines on copepods and other freshwater zooplankton have dealt only on their taxonomy and distribution. Filipinodiaptomus insulanus is a calanoid copepod recognized as endemic to the country with its distribution restricted to the areas of Bulacan, Laguna and other parts of Rizal. Furthermore it is the only calanoid copepod found in the La Mesa Reservoir in Novaliches, Quezon City. This paper is a synthesis of three studies of F. insulanus obtained from La Mesa Reservoir. It aims to provide additional baseline information about the organism, particularly on its postembryonic development, feeding habits, and density fluctuations of its life history stage in the reservoir

Impact assessment of cage culture in Lake Taal, Philippines

Abstract only.The environmental impact of cage culture on water quality of Lake Taal was assessed from March 1996 through February 1997. Three stations were considered namely: Balas, which serves as station 1 (non-cage area) and Sampaloc and Laurel, stations 2 and 3 (cage areas), respectively. Monthly water samples with two replicates were collected using a van Dorn sampler at 0, 5, 10 and 15-m depths in all stations. Below surface water from the inside of the cages was also collected. Water temperature, water transparency, pH, and conductivity were determined in situ. Dissolved oxygen, chloride, NO3, NH3, PO4, and total P were analyzed in the laboratory. Phytoplankton density and algal biomass (through cholorophyll a) and primary productivity indices were determined with the light-and-dark bottle method. Of the water quality parameters, conductivity and DO had significant differences between non-cage and cage areas. Conductivity gave significant difference (P<0.01) between control and cage area during the wet season. Highest conductivity value (2100 µ S/cm) was observed in station 3. Mean values of DO gave significant differences (P<0.05) in the different stations throughout the study period. A decrease of DO to 2.5 mg/1 was observed below 10-m depth around the cage areas. Analysis indicates that cage culture leads to oxygen depletion in the water column. The presence of cage structures decreased the flow rate resulting to weak circulation. The reduced water circulation in effect decreased the supply of oxygen and removal of toxic waste metabolites from the vicinity of the fish farm, and reduced the supply of plankton. These results suggest that the impact of cage culture in Lake Taal is minor but can alter the lake ecosystem if not properly managed. Zoning and continuous water quality monitoring are needed

Some limnological features of the northern shore areas of Volcano Island, Lake Taal

Abstract only.Physico-chemical and biological features of the northern shore areas of Volcano Island, Lake Taal observed at monthly intervals from four stations during the period 1994 and 1996 indicate varied microhabitats inhabited by a variety of plants and animals. Physico-chemical characteristics of surface waters were: temperature, 28-35°C; dissolved oxygen content, 3.5-6.2 ppm; pH, 7.5-8.9; salinity, 0-24 ppt; and conductivity, 1.6-4.3 S cm-1. Substratum types were mainly sandy with pebbles or rocks or sandy-muddy. Characteristic submerged plants were the eelgrass Vallisneria gigantea and filamentous green algae. In the eelgrass region, atyid shrimps, mostly Ciridina gracilirostris, commonly occur. Snails such as Melanoides costellaris and Terebia granifera were the most abundant benthic animals collected. Other invertebrates identified from core samples were Corbicula manilensis, annelids, crustaceans and chironomid larvae

Fish in a man-made lake: what is there to eat? (Ecological studies in La Mesa Reservoir)

Abstract only.Since 1975, a number of ecological studies have been done in La Mesa Reservoir (also known as La Mesa Dam or La Mesa Lake). Eight species of fish are known to occur in the lake; of these species, one is stocked to control the proliferation of algae. The plankton community of the reservoir has been found to be remarkably diverse, with at least 62 species of zooplankton and possibly 70 species of phytoplankton. The high biological diversity is due to this lake being a protected area as it is Metro Manila's main source of drinking water. A confluence of several factors that preserve this condition of high aquatic biodiversity is possible: (1) Little perturbation in its water quality and its watershed occurs. (2) During high water levels, numerous coves and embayments and the moderate depths create a myriad of ecological niches and refuges for the aquatic biota. (3) Plankton diversity is likely enhanced by abundance of edible algal species (for herbivorous zooplankton) and only occasional moderate algal blooms. (4) Low fish predation tolerates large-sized species in the plankton, i.e., Filipinodiaptomus insulanus, a copepod endemic to only a few large areas in Luzon. (5) Nuisance algae are controlled by stocking of tilapia fry and the occasional use of algicide (CuSO4)

Fisheries in the floodplain lakes of Agusan marsh and its implications for sound management

Yearlong assessment of the artisanal fishery from the three floodplain lakes of Ticgon, Dinagat, and Mihaba in Agusan Marsh, a declared national priority protected area, was done using length-weight frequency analyses. Results showed that the catch on economically-important fishes such as Cyprinus carpio and Trichogaster pectoralis in Lakes Ticgon and Mihaba did not suggest growth overfishing. The regulated mesh size allowed in the area is, to some extent, effective. However, Oreochromis niloticus and Trichogaster pectoralis caught from Lake Dinagat were found to have sizes below the optimum and with size less than its length at first maturity. This assessment has a very profound implication to the conservation efforts in the area considering that fishery in the marsh is a cheap source of protein for the local communities. Yet, the continuity of the said regulations remains a formidable challenge for some reasons: community in the marsh is dispersed; the area is so vast with lots of entry and exit points making monitoring a tedious and expensive job; and unabated electrofishing, although declared an illegal activity, is still more profitable than mere use of fishing gears

Preliminary observations on the diel vertical migration of crustacean zooplankton in aquaculture and aquaculture-free areas of Lake Taal, Philippines

Freshwater zooplankton in tropical caldera lakes with intensive aquaculture are exposed to physical, chemical, and biological influences that have differences with other lake types. This study compares the diel vertical migration of crustacean zooplankton between aquaculture and aquaculture-free areas in a tropical caldera lake (Lake Taal, Philippines). Environmental conditions showed little variation in both basins, and crustacean zooplankton showed similar DVM patterns. Wind-induced water movements, volcanic inputs and zooplankton exposure to similar levels of predation influenced zooplankton DVM in the lake. The zooplankton DVM patterns confirm that there is homogeneity in zooplankton composition and distribution in aquaculture and aquaculture-free areas

Variations in microcrustacean (Crustacea: Cladocera, Copepoda) assemblages from selected groundwater-dependent ecosystems in the greater Luzon and Mindoro Island faunal regions (Philippines): insights to tropical groundwater ecology

<p>In the Philippines, the ecology of microcrustaceans from groundwaters and their dependent ecosystems remain poorly understood, yet knowledge about this group can elucidate patterns in groundwater biodiversity to develop sound conservation policies. In this study, microcrustaceans were studied by collecting samples from 102 groundwater-dependent ecosystems, including 51 artesian wells, 23 caves, 14 springs, and 14 piped groundwater pumps during the dry (Nov 2014 to Apr 2015) and wet (May–Oct 2015) seasons. Results indicate the presence of 21 species from Cladocera and Copepoda, including 2 obligate stygobionts and 19 species consist with surface water and facultative stygobiotic taxa. Significant differences in microcrustacean assemblages were noted among types of groundwater-dependent ecosystems (<i>P</i> < 0.05), wherein wells and caves harbored more abundant assemblages with higher total species richness; however, no significant variations were observed between seasons (<i>P</i> > 0.05). Furthermore, principle component analysis revealed that sampling sites were highly characterized by altitude, specific conductivity, and total water hardness. Microcrustacean assemblages in sampled sites were highly dominated by the influence of temperature, dissolved oxygen, and altitude. Species rarefaction analysis revealed low species richness in sampled sites within the region, supporting the existing notion that temperate groundwater-dependent ecosystems were more diverse, and faunal composition in terms of ecological groups is extremely different in tropical and temperate settings.</p

Annotated checklist and insular distribution of freshwater microcrustaceans (Copepoda: Calanoida & Cyclopoida; Cladocera: Anomopoda & Ctenopoda) in the Philippines

This checklist puts together available information on the taxonomy, distribution, and current status of freshwater microcrustacean zooplankton in the Philippines. To date, 81 species have been recorded from Philippine inland waters, including 55 cladoceran and 36 copepod species, in two cladoceran orders (six families); and in two copepod orders (four families). The level of endemicity and distribution patterns of microcrustaceans in the archipelago's freshwater systems reflects the island's origins, biogeographical status, and location in the tropics. However, there are problems: in terms of taxonomy, species level identification is often doubtful and further study on systematics and biogeography is needed to settle conflicts in identification. This is demonstrated by the 29 synonymies and misidentifications detected in previous Philippine records. In addition, the introduction of non-native species of fishes, zooplankton, and other aquatic organisms has begun negatively impacting inland aquatic biodiversity in the country, which is further exacerbated by eutrophication and other environmental changes