360 



FISH HATCHERY MANAGEMENT 



Table 39. classification of ihk behavioral changes ihai occur in fishes 



DURING anesthesia. LEVELS OF ANESIHESIA CONSIDERED VALUABLE TO 

 FISHERIES WORK ARE ITALICIZED. (SOURCE: McFARLAND 19fi0). 



DEFINABLE LEVELS OF ANESTHESIA 



STATE PLANE WORD EQUIVALENTS 



BEHAVIORAL RESPONSES OF FISH 



II 



// 

 /// 



IV 



Normal 



1 Light sedation 



2 Deep sedation 



1 Partial loss of 



equilibrium 



Total loss of 

 equilibrium 



Loss of reflex 



reactivity 

 Medullary collapse 



Reactive to external stimuli, equilibrium 

 and muscle tone normal. 



Slight loss of reaction to external stimuli 

 (visual and tactile). 



No reaction to external stimuli except 

 strong pressure; slight decreased oper- 

 cular rate. 



Partial loss of muscle tone; reaction only 

 only to very strong tactile and vibra- 

 tional stimuli; rheotaxis present, but 

 swimming capabilities seriously dis- 

 rupted; increased opercular rate. 



Total loss of muscle tone; reaction only to 

 deep pressure stimuli; opercular rate 

 decreased below normal. 



Total loss of reactivity; respiratory rate 



very slow; heart rate slow. 



Respiratory movements cease, followed 

 several minutes later by cardiac arrest. 



Carrying Capacity 



The weight of fish that can be safely transported in a distribution unit 

 depends on the efficiency of the aeration system, duration of the haul, wa- 

 ter temperature, fish size, and fish species. 



If environmental conditions are constant, the carrying capacity of a dis- 

 tribution unit depends upon fish size. Fewer pounds of small fish can be 

 transported per gallon of water than of large fish. It has been suggested 

 that the maximum permissible weight of trout in a given distribution tank 

 is directly proportional to their length. Thus, if a tank can safely hold 100 

 pounds of 2-inch trout, it could hold 200 pounds of 4-inch trout, and 300 

 pounds of 6-inch trout. 



Reported loading rates for fishes vary widely among hatcheries, and 

 maximum carrying capacities of different types of transportation units have 

 not been determined. 



Fish loadings have been calculated and reported inconsistently. In the 

 interests of uniform reporting by fish culturists, it is suggested that loading 

 densities be calculated by the water-displacement method. This is based on 



