Control of macrophytes by grass carp (ctenopharyngodon idella) in a Waikato drain, New Zealand

Hornwort (Ceratophyllum demersum L.) and other aquatic macrophytes have historically been mechanically removed from the Rangiriri drain and Churchill East drain to maintain drain efficiency. As an alternative control method for the high plant biomass that accumulates at the end of summer, the effect of stocking diploid grass carp (Ctenopharyngodon idella L.) on the aquatic vegetation was evaluated in these Waikato drainage systems. At the start of the trial, both drains had a low diversity of aquatic macrophytes, and of the nine species (including the emergents), seven were exotic. Two months after grass carp were released to Churchill East drain (the treated drain) the four submerged and floating macrophyte species became scarce in the main drain. Over the same period, these species increased in biomass in Rangiriri drain (the untreated drain), where hornwort became dense and surface-reaching and remained so for the duration of the trial. However, grass carp did not control submerged vegetation in smaller side drains or the shallow, upper parts of the main drain, or the marginal sprawling species and emergent species. The cost of leasing the grass carp was similar to the cost of clearing the drains mechanically, but grass carp provided continuous weed control. However, subsequent to this trial, 62 dead grass carp were found in Churchill East drain in February 2001, and weed cover subsequently increased. This illustrates that grass carp management in New Zealand agricultural drains can be problematic due to periodic fish kills

Comparison of Two Year Classes of Hybrid Grass Carp and Grass Carp for Aquatic Plant Control

Two year classes of grass carp and F, hybrids resulting from bighead carp male x grass carp female were compared at various stocking densities for aquatic plant control. One and two year old grass carp exhibited higher survival rates and better growth rates than the same age hybrid grass carp. The presence of grass carp or hybrid grass carp decreased both Secchi disc transparencies and dissolved oxygen values. Grass carp had a greater negative effect upon these measurements because they removed the vegetation quicker than the hybrid grass carp. These apparent detrimental effects on water quality are necessary trade-offs for vegetation removal by any method. Grass carp and hybrid grass carp utilized Chara sp., Potamogeton pectinatus, Hydrodicton sp., Rhizoclonia sp., and Pithophora sp. Two year old hybrid grass carp required approximately twice as much time as the same age grass carp to eliminate dense growths of the vegetation listed above. One year old hybrid grass carp were slightly less effective than one year old grass carp at controlling these same plant species. However, it was extremely difficult for one or two year old hybrid grass carp to totally eliminate dense growths of these plant species except at high stocking densities. The use of mean vegetation heights to indirectly measure total plant biomass was unacceptable whenever unpreferred floating plant species were present. The hybrid grass carp appeared to be a poor alternative biological control for nuisance aquatic vegetation when compared directly to the grass carp

Population response of triploid grass carp to declining levels of hydrilla in the Santee Cooper Reservoirs, South Carolina

Approximately 768,500 triploid grass carp ( Ctenopharyngodon idella Valenciennes) were stocked into the Santee Cooper reservoirs, South Carolina between 1989 and 1996 to control hydrilla ( Hydrilla verticillata (L.f.) Royle). Hydrilla coverage was reduced from a high of 17,272 ha during 1994 to a few ha by 1998. During 1997, 1998 and 1999, at least 98 triploid grass carp were collected yearly for population monitoring. Estimates of age, growth, and mortality, as well as population models, were used in the study to monitor triploid grass carp and predict population trends. Condition declined from that measured during a previous study in 1994. The annual mortality rate was estimated at 28% in 1997, 32% in 1998 and 39% in 1999; however, only the 1999 mortality rate was significantly different. Few (2 out of 98) of the triploid grass carp collected during 1999 were older than age 9. We expect increased mortality due to an aging population and sparse hydrilla coverage. During 1999, we estimated about 63,000 triploid grass carp system wide and project less than 3,000 fish by 2004, assuming no future stocking. management, population size Ctenopharyngodon idella, Hydrill

The Effects of Grass Carp on Aquatic Plants, Plankton and Benthos in Ponds

The effects of the grass carp (Ctenopharyngodon idella Val.)on aquatic plant biomass, water quality, phytoplankton, chlorophyll a, zooplankton and benthic fauna were investigated between May and September 2000 in earthen ponds at Cifteler- Sakaryabasi Aquaculture and Research Station. (PDF has 8 pages

Fish and macroinvertebrates in lowland drainage canals with and without grass carp

Diploid grass carp (Ctenopharyngodon idella L.) were introduced to a lowland Waikato drainage canal at an initial density of 40-80 kg ha -1(83-167 fish ha -1) to control aquatic macrophytes and improve water flow. A near-by canal was left without grass carp to act as an untreated control. After 7 months, macrophytes occupied 17% of the water column in the treated canal compared to 78% in the untreated canal. Fish and macroinvertebrates in both canals were examined before and after the release of grass carp by sampling with replacement by fyke netting on seven occasions. Brown bullhead catfish (Ameiurus nebulosus (Lesueur)) and shortfinned eels (Anguilla australis Richardson) comprised most of the resident fish biomass in both canals; however, before grass carp stocking, eels were more abundant than catfish in the treated canal. There was no change in the abundance of resident fish after stocking, but young-of-the-year catfish had greater mortality and grew faster in the treated canal than in the untreated canal. Macroinvertebrates were primarily associated with aquatic macrophytes. Grass carp reduced aquatic macrophyte abundance in the treated canal by about 80%, which by inference reduced the abundance of associated macroinvertebrates, but there was no observed impact of grass carp stocking on the resident fish assemblage. We examined the relationship between head width and fish length, and from this determined that 70% of the grass carp could have escaped through the downstream retention screen. Despite this possibility, grass carp remained in the canal and effectively controlled aquatic macrophytes for 18 months

Skistodiaptomus pallidus (Copepoda: Diaptomidae) establishment in New Zealand natural lakes, and its effects on zooplankton community composition

The North American calanoid copepod Skistodiaptomus pallidus is an emerging invader globally, with non-indigenous populations recorded from constructed waters in New Zealand, Germany and Mexico since 2000. We examined the effects of S. pallidus establishment on the zooplankton community of a natural lake, Lake Kereta, where it was first recorded in late-2008, coincident with releases of domestically cultured grass carp (Ctenopharyngodon idella). Although not present in any of our samples prior to August 2008, S. pallidus was found in all samples collected in the subsequent five years. ANOSIM indicated zooplankton community composition significantly differed between samples collected before and after S. pallidus invasion, whether the invader was included in the analysis or not. Zooplankton species affected most greatly were the copepods Calamoecia lucasi and Mesocyclops sp., which decreased in their relative importance, and the cladocerans Bosmina meridionalis and Daphnia galeata, which increased. Rotifer species were relatively unaffected. As the length of grass carp released were >6.5 cm, direct predatory effects by this species on the zooplankton community are unlikely. Associated reductions in macrophyte biomass could explain increases in the relative abundances of planktonic cladocerans (B. meridionalis and D. galeata). However, the effect of macrophyte reduction by grass carp on zooplankton communities is considered to be limited elsewhere, while the reduced macrophyte biomass cannot explain the decrease in relative abundance of the native planktonic calanoid copepod C. lucasi. Competition between C. lucasi and S. pallidus is the most compelling explanation for the reduction in importance of the native calanoid copepod species. Skistodiaptomus pallidus appears to have undergone a “boom-and-bust” cycle in Lake Kereta, increasing in relative abundance in the first three years following establishment, before declining in importance

Evaluation of macrophyte control in 38 Florida lakes using triploid grass carp

Florida’s large number of shallow lakes, warm climate and long growing season have contributed to the development of excessive growths of aquatic macrophytes that have seriously interfered with many water use activities. The introduction of exotic aquatic macrophyte species such as hydrilla ( Hydrilla verticillata ) have added significantly to aquatic plant problems in Florida lakes. The use of grass carp ( Ctenopharyngodon idella ) can be an effective and economical control for aquatic vegetation such as hydrilla. Early stocking rates (24 to 74 grass carp per hectare of lake area) resulted in grass carp consumption rates that vastly exceeded the growth rates of the aquatic plants and often resulted in the total loss of all submersed vegetation. This study looked at 38 Florida lakes that had been stocked with grass carp for 3 to 10 years with stocking rates ranging from < 1 to 59 grass carp per hectare of lake and 1 to 207 grass carp per hectare of vegetation to determine the long term effects of grass carp on aquatic macrophyte communities. The median PAC (percent area coverage) value of aquatic macrophytes for the study lakes after they were stocked with grass carp was 14% and the median PVI (percent volume infested) value of aquatic macrophytes was 2%. Only lakes stocked with less than 25 to 30 fish per hectare of vegetation tended to have higher than median PAC and PVI values. When grass carp are stocked at levels of > 25 to 30 fish per hectare of vegetation the complete control of aquatic vegetation can be achieved, with the exception of a few species of plants that grass carp have extreme difficulty consuming. If the management goal for a lake is to control some of the problem aquatic plants while maintaining a small population of predominately unpalatable aquatic plants, grass carp can be stocked at approximately 25 to 30 fish per hectare of vegetation

Действие температурного фактора на морфометрические и физические показатели эритроцитов и полиморфноядерных лейкоцитов Ctenopharyngodon idella

Оценка влияния температурного фактора на морфометрические и физические показатели эритроцитов и полиморфноядерных лейкоцитов белого амура Ctenopharyngodon idella методом атомно-силовой микроскопи

Pregled nekih hemijskih jedinjenja i masnih kiselina u mesu gajenog šarana (cyprinus carpio) i belog amura (ctenopharyngodon idella)

This study was conducted to determine of some chemical compounds (proteins, lipids, moisture and ash) and fatty acids in cultured two species of common carp (Cyprinus carpio) and grass carp (Ctenopharyngodon idella). Results of this study showed that the amount of saturated fatty acids (SFA) in common carp and grass carp were 35.21 ± 2.19% and 27.18 ± 2.63%, respectively and saturated fatty acids (SFA) in common carp was higher compared to grass carp (p0.05). This study showed that PUFA was higher than SFA in Grass carp while SFA was higher than PUFA in common carp. There were significant differences in protein, lipid and moisture in two species (p0.05)

Feeding Behavior, Food Consumption, Growth, and Survival of Hybrid Grass Carp (Hypophthalmichthys nobilis x Ctenopharyngodon idella) In South Dakota

Plant preference of yearling hybrids (Hypophthlmichthys nobilis X Ctenopharyngodon idella) was examined under control conditions at the Gavins Point National Fish Hatchery, Yankton, South Dakota and under field conditions in two stockwater impoundments in south-central South Dakota. IN feeding trials, conducted in a 0.07 ha hatchery pond, hybrid grass carp selected Najas guadalupensis, Chara sp. and Potamogeton pectinuatus. Ceratophyllum demersum and Myriophyllum spicatum were not consumed. Under field conditions N. guadalupensis also appeared to be preferred while C. demersum was not. Feeding behavior, daily consumption, growth, and survival were also evaluated in the two stockwater impoundments. Hybrids averaging 51g were stocked in the ponds at rates of 17 and 31 kg/ha. No discernible control of aquatic vegetation was attained by the hybrids at these stocking rates. Feeding activity of the hybrids was diurnal and took place primarily in shallow water. The hybrids fed most heavily from 0400 to 0800 and from 1600 to 2000. Total daily consumption was 44.0% of body weight at 23 C and 30.4% at 15 C. Several of the hybrids from 24 April 1982 to 18-19 September 1982 was 59.1 and 32.3% in Ponds 1 and 2 respectively. Hybrids surviving to the end of this period averaged 542g in Pond 1 and 591g in Pond 2, representing 3.3 and 3.6 g/day growth rates