Effectiveness of the Air Stripping in Two Salmonid Fish, Rainbow Trout (Oncorhynchus Mykiss) and Brown Trout (Salmo Trutta Morpha fario)

Summary

The principal aim of this study is to standardize and test the pneumatic method (air stripping) of collecting eggs in rainbow trout and brown trout. This method allows effective and simple collection of the eggs without the necessity of fish abdomen massage.

Abstract

Egg collection is one of the most crucial procedures during fish reproduction in salmonid hatcheries. Classic methods involve the use of hand massage on fish abdomens to expel the eggs. An alternative method uses the pressure of gas injected into the body cavity, which causes the subsequent release of the eggs. This method is believed to have less negative effects on both the welfare and egg quality of the broodstocks. Herein, we compare the results of air and hand stripping methods with respect to one-year survival and egg quantity and quality in two salmonid fish, rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta morpha fario). Our results indicate that air stripping yielded a better quality of eggs and higher one-year survival rate in rainbow trout. In addition, air stripping resulted in lower mortality rate than the group subjected to hand stripping (25% vs. 35%). The pH and hatching rate of the hand stripped group was lower than those of the air stripped group. In the case of brown trout, the quality of eggs obtained by both hand and air-stripping methods was similar; however, the one-year losses in fish were higher in air stripped group (15% compared to 0% in hand stripped fish). Although the advantages of air stripping method over hand stripping in terms of egg quality might not be observed in all salmonid species, the air-stripping procedure might be a promising option to be adopted in hatcheries as it ensures a high level of reproducibility and efficiency.

Introduction

The rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta morpha fario) belong to the Salmonidae family of Salmoniformes¹. The production of these two species in global aquaculture has gained rapid growth, owing to their commercial and recreational importance. In Poland, production of salmonid fish stands at around 20 000 tonnes, with rainbow trout being the dominant species. On the other hand, the brown trout represents a major source of freshwater fish resources in Europe because of its commercial value in aquaculture and importance for angling. In many aquatic ecosystems, the existence....

Protocol

Procedures were carried out in accordance with the Local Committee on the Ethics of Animal Experiments in Olsztyn, Poland.

1.Equipment Preparation

1. Use a syringe and needle for injection of the gas into the fish body cavity.
2. Set the gas pressure at 0.5 bar, and maintain this pressure to be below 1 bar throughout.
3. Control the air flow. For the salmonid fish, 1.5 L/min is the most efficient speed of gas exhaustion. Maintain the optimum speed because higher speed might not obtain all the eggs while a slower speed might unnecessarily prolong the procedure.
4. Connect the syringe with a screwed needle (0.8-1....

Results

Mature males and females of rainbow trout (age 2+, 1700 ± 328 g) and brown trout (age 3+, 1900 ± 435 g) were obtained from the Salmonid Fish Hatchery (Rutki-Żukowo, Inland Fishery Institute in Olsztyn, Poland). The males and females were placed in separate tanks with a volume of about 5 m³. The water temperature was 12±1 °C. Before manipulation, fish were anesthetized with 0.2% Propiscin. The fish were divided into two groups. Part of them underwent a traditional m.......

Discussion

The pneumatic method of egg collection from fish, although more time-consuming than the traditional method (hand stripping), can secure a high quality of matured oocytes (this work). This is related to the low risk of mechanical disruption of the eggs while applying this procedure. High pH of the ovary fluid, as well as an increase in the fertilization rate, attest to the usefulness of the pneumatic method. Overall, the air stripping method of egg collection in fish reproduction could be a promising option in terms of st.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Glycine pure P.A.	AVANTOR	527560117	sperm activating buffer
Trizma base	Sigma Aldrich	T1503	sperm activating buffer
Sodium chloride Bioreagent	Sigma Aldrich	S5886	sperm activating buffer
Calcium chloride anhydrous	Sigma Aldrich	C4901	sperm activating buffer
Propiscin (0.2% etomidate solution)	IRS Olsztyn, Poland	not indicated
compressor	Thomas  Sheboigan WI USA	DT/SR 070800001882
reduction valve	Camozzi	cRJUS U7J
air hose	ZEC T.P.U.	SH.98
syrgine	EFD	7012118
Air spawning stage	Biopasz, Poland	PNEU001
Orion Ross Ultra electrode	Thermo Scientific, Waltham, MA, USA	8102BNUWP