Presence Of Tilapia Research Articles

The Distribution of Invasive Tilapia Throughout A Tropical Man-Made Lake With Special Reference to Temengor Reservoir, Malaysia

With a surface area of 15, 200 ha, the Temengor Reservoir, in the northwestern state of Perak was selected among other lakes in Malaysia for the development of a large tilapia aquaculture facility in 2008 due to its favourable environmental conditions. Tilapia has never been recorded at Temengor Reservoir prior to the establishment of this facility. However, preliminary observations in a previous study detected tilapia species in the natural waters of this lake, strongly suggesting these were escapees from the floating cages which had invaded the natural waters. Following that, a study was conducted to assess the distribution of these escapees throughout the Temengor Reservoir. The cultured tilapias are easily recognizable with elongated mouth and body, and long caudal fin. The sampling was conducted using gill nets. The distribution of the escaped tilapia throughout the Temengor Reservoir was mapped based on previous data and current data on the fish checklist conducted at different sampling points of this lake, and the occurrence (presence/absence) of escaped tilapia was recorded. A comparative analysis was conducted at several number of points among three sampling areas, according to the radii from the fish cage facility; <5km (S1), 5-15km (S2), and >15km (S3). The ANOVA showed significant differences (p<0.05) in Catch per Unit Effort (CPUE) weight between the three sampling areas. As tilapia is a highly successful global invasive species, the presence of tilapia at these and other locations at Temengor Reservoir should be rigorously monitored. Complete eradication of tilapia in the lake is of high urgency. We recommend intensive targeted fishing of the species in the vicinity of the cages and biological control by native predators to preserve and conserve the native fish species at Temengor Reservoir.

Effects of Nile Tilapia (Oreochromis niloticus) on phytoplankton community structure and water quality: a short-term mesocosm study

Nile tilapia is a highly invasive fish species, deliberately introduced into many lakes and reservoirs worldwide, sometimes resulting in significant ecosystem alterations. A short-term mesocosm experiment with and without Nile tilapia (Oreochromis niloticus) was designed to test the hypotheses that the presence of tilapia may affect phytoplankton community structure, increase nutrients availability in water column and deteriorate water quality. Nutrients, total suspended solids (TSS) and biomass of phytoplankton in different size classes (as Chla) were measured. We found that tilapia increased the total nitrogen (TN), total dissolved nitrogen (TDN), NH4+and TSS concentrations, deteriorating the water quality. In addition, under tilapia presence, the biomass of phytoplankton, as well as that of micro- and nano-phytoplankton, increased leading to a change in the structure of the phytoplankton assemblage. Moreover, a reduction in the biomass of periphyton was observed. Omnivorous tilapia is often dominant in tropical and subtropical waters, and removal of this fish may represent an effective management tool to improve the water quality.

Growth and nutrient conversion of white shrimp Litopenaeus vannamei (Boone) and Nile tilapia Oreochromis niloticus L. in an integrated closed recirculating system

We investigated the eiects of the stocking density of white shrimp (Litopenaeus vannamei )o n shrimp and tilapia growth and nutrient conversion in an integrated closed recirculating system both with and without Nile tilapia (Oreochromis niloticus). A 2 � 3 factorial design involving tilapia presence/ absence and shrimp stocking densities of 40, 80 and 120 m � 2 was applied, using a tilapia:shrimp ratio of 0.025. There were no signi¢cant interactions between tilapia presence and shrimp stocking density in terms of shrimp growth performance or feed utilization. The presence of tilapia had no eiect on the shrimp growth rate, survival rate or total weight gain (%). Shrimp growth declined signi¢cantly with increased shrimp stocking density, but the growth of tilapia was not signi¢cantly diierent among the three shrimp densities tested. The conversion of feed nitrogen and phosphorus into total harvested animal biomass was signi¢cantly higher in the presence than in the absence of tilapia. The nutrient conversion rate at the lowest shrimp density (40 m � 2 ) was signi¢cantly higher than at the highest density tested (120 m � 2 ).

Salinity and fish effects on Salton Sea microecosystems: benthos

The Salton Sea, the largest lake in California, has a surface elevation 69 m below sea level which is maintained predominantly by the balance of agricultural runoff and evaporation. The lack of outflowing streams is resulting in a gradual buildup of salts in the lake, increasing the salinity. A 15 month microcosm experiment was conducted to determine the effects of salinity and tilapia ( Oreochromis mossambicus) on an assemblage of benthic and planktonic Salton Sea algae and invertebrates. This article reports the responses of the benthic invertebrates. Microcosms (312 l fiberglass tanks) were set up without tilapia at 30, 39, 48, 57, and 65 g · l-1. Additional microcosms were set up with tilapia at 39 and 57 g · l-1. In the absence of fish Gammarus mucronatus dominated the benthos at the lower salinities, and Trichocorixa reticulata and the larvae of Ephydra riparia were most abundant above 48 g · l-1. The most abundant meiofaunal species included the harpacticoid copepod. Cletocamptus deitersi, three nematodes, the rotifer Brachionus plicatilis, ciliates, including Condylosoma sp. and Fabrea salina, two foraminiferans including Quinqueloculina sp., and a large flagellate. Most meiofaunal species responding to salinity were most abundant at 65 g · l-1, especialy after 6 months when Gammarus dominated the lower salinities. The tilapia reduced the abundance of macrofaunal species, especially at 39 g · l-1, and generally increased the abundance of meiofaunal species and ciliates. The microcosm benthic macro- and meiofaunal communities were most likely structured by Gammarus, salinity and tilapia. Gammarus reduced the other species by predation and changing the detritus from an algal base to a fecal pellet base. Gammarus was itself reduced by tilapia and by reduced reproductive success above 39 g · l-1. More species were therefore able to compete at higher salinities and in the presence of tilapia. Tilapia also affected the benthos by depositing loosely packaged fecal material which may support more meiofaunal species than either the robust Gammarus fecal pellets that were abundant at 39 g · l-1 or the algae-fecal pellet mix at 57 g · l-1.

Salinity and fish effects on Salton Sea microecosystems: zooplankton and nekton

The Salton Sea is the largest inland lake in California. Currently (1997) the salinity of the lake is about 44 g l-1 and is increasing gradually as a result of continued agricultural wastewater inflows, high evaporation rates, and lack of an outlet. A microcosm experiment was carried out to determine the effects of salinity (30, 39, 48, 57, and 65 g l-1) on Salton Sea algae and invertebrates in outdoor aquatic microcosms. The experiment was also designed to assess the effects of tilapia ( Oreochromis mossambicus) on this community at two of these salinities (39 and 57 g l-1). Fiberglass tanks containing Salton Sea water were adjusted to the appropriate salinity by the addition of salts, identically inoculated with organisms from the Salton Sea and other saline water bodies in the region, and monitored for 15 months. Planktonic and nektonic invertebrates were sampled monthly at night from the upper part of the water column. The dominant invertebrates present were Gammarus mucronatus, Artemia franciscana, Trichocorixa reticulata, and an assemblage of ciliate protozoans. Gammarus decreased and Trichocorixa increased with increasing salinity. Artemia was present only at the two highest salinities. Rotifers, harpacticoid and cyclopoid copepods, barnacle larvae, and protozoans all showed marked and varied responses. During the latter half of the experiment, the invertebrate assemblage was dominated by Gammarus at 30 and 39 g l-1, by protozoans at 48 g l-1, and by protozoans and Trichocorixa at 57 and 65 g l-1. The presence of tilapia caused a 99 percent reduction in Gammarus at 39 g l-1 and a 70–90 percent decrease in Trichocorixa at 57 g l-1. These were accompanied by substantial increases in rotifers, copepods, and certain protozoans, and decreases in other protozoans. As the salinity of the Salton Sea continues to increase, large changes in the invertebrate populations are expected. This study suggests that the principal change would be an increase in Trichocorixa densities, the loss of Gammarus, and the appearance of Artemia at about 60–70 g l-1, when both fish and invertebrate predators are likely to be scarce or absent. Protozooplankton abundance is likely to increase when tilapia declines and later decrease when and if large Artemia populations develop.

Polyculture of Nile tilapia ( Oreochromis niloticus) and Australian red claw crayfish ( Cherax quadricarinatus) in earthen ponds

Nile tilapia ( Oreochromis niloticus) and Australian red claw crayfish ( Cherax quadricarinatus) were cultured alone and together in replicat 0.02 ha earthen ponds to assess the nature and intensity of species interaction in polyculture. Treatments were: (I) 10000 tilapia per hectare, (II) 10000 tilapia plus 25000 crayfish per hectare and (III) 25000 crayfish per hectare. All ponds were fed a 32% crude protein, pelleted catfish feed at monthly-adjusted rates based on stocked tilapia biomass. After 100 days of polyculture, ponds were harvested. Tilapia growth, reproduction and food conversion were adversely affected by the presence of crayfish ( P<0.01). Crayfish growth, incidence of intersexuality and percentage of berried females were not affected by the presence of tilapia ( P<0.01).

POLYCULTURE OF CHANNEL CATFISH (Ictalurus punctatus) WITH ALL‐MALE TILAPIA HYBRID

AbstractChannel catfish (Ictalurus punctatus) (x̄ = 0.8 g) and all‐male hybrid tilapia fingerlings (Sarotherodon mossambica ♂ × S. hornorum ♀) (x̄ = 35.0 g) were stocked in 0.04 ha replicated ponds in Baton Rouge, Louisiana, in March and July 1981, respectively. The ponds were stocked at densities of 11,110 catfish per ha, 11,110 catfish with 5,550 tilapia per ha, 7,400 catfish per ha, and 7,400 catfish with 3,700 tilapia per ha. The fish were fed daily at 4% of estimated catfish biomass and were harvested in November 1981.There were no differences in dissolved oxygen or water temperature among the four culture systems (P &gt; 0.05). The presence of tilapia, however, significantly increased water turbidity, pH and chlorophyll a concentrations (P &lt; 0.05). Tilapia did not improve water quality and may have deteriorated it. Tilapia did not affect channel catfish growth or production (P &gt; 0.05), but the presence of tilapia did significantly increase total fish yield (P &lt; 0.05) by 13.5 and 32.2% at low and high catfish densities, respectively. Channel catfish and tilapia averaged 390 and 245 g at harvest, respectively. Overall catfish survival averaged 61%. Tilapia survival was 72% and 61% at low and high densities, respectively.