Efficacy of formalin, iodine and sodium chloride in improvement of egg hatching rate and fry survival prior to the onset of exogenous feeding in yellow perch

Abstract

Egg disinfection is considered the most important routine work in hatcheries to avoid fungal and/or bacterial infection of fish eggs. The aim of this study was to determine the effectiveness of three disinfectants: formalin, iodine and sodium chloride on the hatching success of yellow perch eggs. The disinfectants were tested in triplicate at different concentrations for 15 and 30 min bath treatments. Two experiments were conducted; formalin at five concentrations (25, 50, 100, 150 and 200 mg L−1) and 25 mg L−1 iodine were tested in the first experiment. The second experiment involved formalin at three concentrations (250, 500 and 1000 mg L−1), iodine at three concentrations (50, 100 and 250 mg L−1) and sodium chloride at three concentrations (500, 1000 and 3000 mg L−1) were used. Iodine and sodium chloride‐treated eggs hatched earlier than formalin‐treated eggs. The highest mean percentage of eyed stage, hatching rate and survival to first feeding fry was observed at 200 mg L−1 formalin for 30 min, 50 mg L−1 iodine for 15 min and 500 mg L−1 sodium chloride for 30 min. High concentrations of formalin (1000 mg L−1), iodine (250 mg L−1) and sodium chloride (1000 and 3000 mg L−1) showed toxicity to yellow perch eggs, resulting in low hatching rate and survival to first feeding fry. We recommended formalin at a concentration of 150–200 mg L−1 for 30 min as an effective, easily available and low‐cost disinfectant for routine use to improve yellow perch hatchability.

Evaluation of Two Formalin Concentrations During Yellow Perch Egg Incubation

“…The results of this study showing no decrease in survival associated with the highest formalin concentration differ from those seen by Abd El-Gawad et al (2015). They reported that daily, 15-min 1000 mg/L formalin treatments significantly decreased yellow perch egg survival compared to lowered formalin concentrations of 250 and 500 mg/L.…”

“…Higher water temperatures increase formalin toxicity (Piper et al, 1982). Formalin concentrations of greater than 500 mg/L have also been shown to increase fish egg incubation times (Akpoilih & Adebayo, 2010;Abd El-Gawad et al, 2015). However, no differences in hatching times between formalin treatment concentrations in this study were observed.…”

“…The use of formalin or other preservatives in other studies documenting larval yellow perch length (Mansueti, 1964;Hokanson & Kleiner, 1974;Clady, 1976;Ney, 1978) is unknown. Other possible explanations for the reduced size of larval perch observed in this study include maternal characteristics (Heyer at al., 2001;Raventos & Planes, 2008), possible premature hatching due to physically moving the eggs (Hokanson & Kleiner, 1974), and potential formalin toxicity during the early stages of yellow perch development (Abd El-Gawad et al, 2015). Because both starvation and predation of larval fishes are size dependent (Miller et al, 1988), subsequent survival of larval yellow perch with reduced size may be reduced.…”

“…Although Abd El-Gawad et al (2015) and Hart et al (2006) observed positive effects from treating perch eggs with relatively low formalin concentrations, Soupir and Barnes (2006) reported that formalin concentrations lower than 1667 mg/L resulted in reduced walleye (Sander vitreus) egg survival during hatchery incubation. However, formalin tolerance varies by species (Rach et al, 1997) and the use of concentrations greater than 1000 mg/L for 15 min may reduce yellow perch egg survival (Abd El-Gawad et al, 2015). Some of the inconsistency with these results is likely due to differences in incubation water chemistry (Barnes et al, 2004).…”

“…Historically, virulent water mold populations have required daily, 15-minunte formalin treatments of 1667 mg/L during egg incubation at Blue Dog State Fish Hatchery near Waubay, South Dakota, USA. However, the use of a lower formalin concentration has not been investigated for yellow perch and recent results indicate that concentrations greater than 1000 mg/L can reduce their egg survival (Abd El-Gawad et al, 2015). Thus, the objective of this study was to compare the effects of a reduced formalin concentration of 834 mg/L with the established standard of 1667 mg/L throughout yellow perch egg incubation on egg survival, hatching rate, fry length, and water mold control.…”