Performance of Larval Walleye Cultured Intensively in Clear and Turbid Water¹

Abstract

Experiments were conducted to determine the performance of larval walleye (Stizostedion vitreum) reared in clear, 0.2 nephelometric turbidity units (NTU), and turbid water, 20 or 50 NTU, on formulated feed. Larvae were cultured for 21, 28, or 30 days posthatch in four trials with 3 or 4 replicate tanks per treatment (clear and turbid) in each trial. Duration of each trial was dependent on the arrival of newly hatched larvae for subsequent trials. The desired turbidity levels were obtained by pumping a solution of clay to the culture tanks every 20 (trial 1) or 30 min (trials 2, 3 and 4). Other than turbidity, all environmental conditions (dissolved oxygen, alkalinity, pH, total ammonia, un‐ionized ammonia, nitrate, nitrite, chloride, and hardness) and rearing techniques were similar between treatments. Larvae were stocked at 20/L and fed formulated feed (Fry Feed Kyowa B‐400 and B‐700) every 3 to 7 min, 24 hours per day. Significant differences in feed acceptance and total length between larvae in the clear and turbid water were observed as early as 7d posthatch. Larvae in turbid water began eating the formulated diet one to two days before those in clear water. In all trials, survival, final length, and final weight of larvae reared in water of high turbidity were significantly greater than for larvae reared in clear water. Mean survival (±SE) for all four trials was 27.7 ± 5.6% in high turbidity water and 5.9 ± 1.3% in clear water. At the end of the trials, mean total length of the larvae reared in turbid water was at least 3.2mm (15%) greater than that in the clear water. Mean final weight of the larvae from turbid water was 2.25 times greater than larvae from clear water over the four trials. In two of the four trials, gas bladder inflation (GBI) of larvae reared in high turbidity was significantly greater than for fish reared in clear water, but the difference in GBI was not significant in the other two trials. In this study, performance of larval walleye was greatly enhanced by water with a turbidity of at least IS NTU.

Intracohort cannibalism and methods for its mitigation in cultured freshwater fish

“…In Eurasian perch, the greatest growth in weight and length was observed in tanks with light grey and white walls, which were strongly illuminated, while the lowest growth was recorded in a tank with black walls and 250 lx illumination (Tamazouzt et al 2000). Moreover, in Eurasian perch, light walls seems to induce a strong contrast between brown-yellow food particles and the tank walls and, consequently, improve food perception as observed in some other fish species, such as seabream Sparus auratus (Ounais-Guschemann 1989) and walleye (Bristow and Summerfelt 1994).…”

Endocrine and gonadal changes during the annual reproductive cycle of the freshwater teleost,Stizostedion vitreum

“…The ability to produce walleye larvae over this interval could have important advantages for walleye propagation and culture. First, it could allow double-or triple-cropping of existing intensive fry culture systems (e.g., as described by Bristow and Summerfelt 1994). Second, it could be used to increase the interval over which research on the intensive culture of walleye fry can be conducted.…”

Culture Methods of Eurasian Perch and Yellow Perch Early Life Stages

“…Once feed intake is initiated, the larvae continue to ingest feed regardless of tank size, and the clinging and non-feeding behaviors disappear. The addition of clay to make the water turbid (up to 50 NTU) and to increase light diffusion has been recommended for walleye larvae by Bristow and Summerfelt (1994). Algae suspension was successfully applied to yellow perch and in this case the turbidity was in the range of 10-15 NTU during the first 10-12 days of rearing (Kwasek et al 2013).…”