Gerald M. Ludwig

Effects of trichlorfon, fenthion, and diflubenzuron on the zooplankton community and on production of reciprocal-cross hybrid striped bass fry in culture ponds

Abstract The application of trichlorfon, diflubenzuron, or fenthion to fertilized culture ponds stocked with 5-day-old, reciprocal-cross, hybrid striped bass fry resulted in an initial reduction in the concentration of rotifers and longer-term alteration of zooplankton successional stages, including changes in concentrations of rotifers, cladocerans, and copepods. Culture ponds without applied chemicals had the highest concentrations of small rotifers when fry were stocked, followed by high concentrations of cladocerans, copepod nauplii, and adult copepods. Fry survival in untreated ponds was higher than in chemically-treated ponds. Initial high concentrations of copepods in some ponds corresponded with low fry survival. Untreated ponds that were filled at the time of broodfish spawning, and stocked with fry 5 days later, had the highest fry survival rates, corresponding with peak rotifer concentrations, followed by a typical zooplankton succession.

Effects of common aerially applied rice herbicides on the plankton communities of aquaculture ponds

Abstract Ten common aerially applied herbicides for rice were tested for possible adverse impacts on pond phytoplankton and zooplankton and critical water quality variables. Treatments simulated direct spraying of ponds and amounts of drift judged able to reach the pond at 1/10 and 1/100 direct rates. The study was conducted in 12, 500-l outdoor pool mesocosms. Pond water from an adjacent baitfish rearing pond was used. Water quality measurements were made prior to application and at 24 and 48 h after application. Commercial compounds tested and direct rates in kg active ingredient ha −1 were clomazone (0.6), thiobencarb (3.4), pendamethalin (1.1), propanil-dry, flowable (4.5), quinclorac (0.6), halosulfuron (0.07), bensulfuron methyl (0.07), triclopyr (0.4), 2,4- d -amine (1.7), and molinate (5.6). In addition, propanil was evaluated in a second application scenario at the same rates and to the same pond water sample as the initial application. Except for propanil, the rice herbicides produced no measurable effect on pond plankton or associated water quality. Following the first application at full rate for propanil, morning oxygen levels were reduced to critical levels (below 3 mg/l) for 2 days. After a second application of propanil at the full and 1/10 rates, oxygen levels were not decreased, although there were significant increases in chlorophyll a and zooplankton concentrations.

Technical Notes: Estimating Numbers of Golden Shiner Eggs on Spawning Mats

Abstract A method for estimating numbers of eggs of golden shiners (Notemigonus crysoleucas) on spawning mats was developed and tested. Eggs were removed from small plugs of mat material with 1.5% sodium sulfite solution. These samples were highly correlated with total egg numbers determined volumetrically.

Hatching Rates of Golden Shiner Eggs in Tanks

Abstract Egg-hatching rates for golden shiners (Notemigonus crysoleucas) on spawning mats were calculated by estimating egg numbers on nine mats, holding mats in separate tanks, and estimating fry numbers 3 d after hatching. Mean hatching success was 22.5%. The number of fry hatched was directly proportional to the number of eggs on a mat.

SEASONAL GROWTH AND SURVIVAL OF ROSY RED AND NORMAL-COLORED FATHEAD MINNOWS RECEIVING DIFFERENT FEED RATIONS

Abstract Rosy red (RRFM) and normal-colored (NCFM) varieties of the fathead minnow Pimephales promelas were reared in 0.04-ha ponds and fed at 3% or 0.3% body weight daily from August to November or grown in 0.1-ha ponds and fed at 2% or 0.1% of body weight from November to April. Normal-colored fathead minnows harvested in November had significantly (P ≤ 0.05) higher numerical yield rates than RRFM. Rosy red fathead minnows harvested at that time had significantly higher individual weights and coefficients of condition than NCFM. Net production of both varieties of minnows fed at 3% body weight and harvested in November was nearly three times that of fish receiving the 0.3% ration. Greater yield rates and heavier individual weights for fish receiving the higher ration accounted for the higher production. At the April harvest, NCFM had higher coefficients of condition than RRFM. Biomass of the two color varieties of fish fed the 2% ration and harvested in April was twice that of fish that received the 0.1...

Comparison of channel catfish, Ictalurus punctatus, and fathead minnow, Pimephales promelas, production and water quality among a polyculture and two monoculture systems

Abstract Production of channel catfish and fathead minnows was compared in three culture methods: two-pond polyculture (water interchanged between ponds containing catfish and those containing minnows), single-pond monoculture, and circulated-water monoculture. Improvement in catfish production and water quality appeared to be related to water movement in the circulated treatment and water movement and dilution in the polyculture treatment. Fathead minnow production in the polyculture treatment was comparable to low intensity commercial culture. High clay turbidity received from the catfish ponds may have depressed primary production, levels of plankton standing crops, and fish survival and growth in the fathead minnow polyculture treatment below that in the other two treatments.

Relation between Bar Grader Size and Size of Striped Bass

Abstract Regression equations and a table that express the relation between bar grader spacing and total lengths and weights were determined for 5–7-month-old striped bass (Morone saxatilis).

Communications: Growth and Survival of Two Color Varieties of Fathead Minnows in Deep and Shallow Ponds

Abstract Fathead minnows (Pimephales promelas) of normal and rosy red color varieties were cultured under similar conditions in shallow (average depth, 0.6 m) and deep (1.1 m) 0.1-ha ponds from August to October 1992. Rosy red fathead minnows had slower growth rates and lower coefficients of condition (weight : length3) than normal-colored fathead minnows. Survival and total pond production did not differ between the color varieties in shallow or deep ponds. Mild weather conditions may have obscured the potential effects of pond depth on production and growth.

Row Crop Herbicide Drift Effects on Water Bodies and Aquaculture

Aquatic ecosystems produce substantial amounts of aquatic products; including all new sources of seafood, from aquaculture. Level land with clay soils and the availability of water supplies makes riverine alluvial plains favorable areas for row crops and aquaculture. Aquaculture ponds are susceptible to impacts from row crop production through drift of herbicides. To assess these impacts we have conducted field research in replicated mesocosms filled with water and associated naturally-occurring communities from various pond ecosystems and subjected to expected levels of drift from all major aerially-applied herbicides currently in use. Rather than an organismal approach and LC50’s, data indicates community-level approaches better approximate ecosystem impacts. Herbicide drift that affects phytoplankton adversely or in a stimulatory manner will similarly impact the ecosystem, as phytoplankton produce oxygen, take up ammonia and nitrite and provide food for zooplankton. Drift levels are below toxic levels to most other aquatic organisms, including fish (Spradley, 1991). Drift amounts reaching water bodies and ponds, including fish ponds, depend on many factors, but the cumulative range is most affected by the size of the water body. Thus, other than in direct overflight, larger catfish ponds (6-8 ha) have a drift range of 1-10% and smaller more recent designs of 4 ha, 5-20%. Even smaller ponds, used for fingerling production and baitfish production (0.8-2 ha), may receive drift amounts of up to 30% of the field rate.Herbicide drift may be expected to impact small water bodies through death or reduction in the photosynthetic rats of phytoplankton, which could reduce the supply of dissolved oxygen, inhibit removal of toxic nitrogenous wastes, and reduce production of zooplankton by reducing their food supply. These conditions could also result in death, disease, or lower growth rates of managed or cultured fishes. Triazine herbicides (atrazine and simazine), as well as amides (propanil), phenylureas (diuron), triazones, uraciles and phenolics, act through inhibition of photosystem II (PSII) of photosynthesis (Cobb, 1992). They are widely used in agriculture, since they provide a low-cost basal weed control (Jay et al., 1997). Using mesocosms and naturally-occurring plankton communities in a multi-day study provides better extrapolations to real environments than laboratory studies on a single species (Juettner et al., 1995), and possibly prevent overestimate of impacts (Macinnis-Ng and Ralph, 2002). The major drift source is aerial application, with an