on genetic studies of three species of rockfish (Sebastodes 

 auriculatus, S. caurhius, S. elongatus). The aim is to de- 

 fine biochemical differences among as many species as pos- 

 sible and to use these differences for species identification 

 of larvae (positive identification is not successful with present 

 methods) . 



Growth and Mortality 



The most important discovery from groundfish research 

 was made by comparison of ages and lengths of coastal 

 and Puget Sound hake. Most of the fish in both areas were 

 4, 5, and 6 years old. The coastal hake were mostly larger 

 (16-24 inches) than the Puget Sound hake (12-16 inches). 

 Lengths of hake of like age in the two areas showed little 

 overlap. Both length-frequencies and age-frequencies imply 

 different growth and mortality in the two populations. The 

 length-frequency and availability data provide strong evi- 

 dence, supported by genetic evidence, that Puget Sound and 

 coastal hake are racially distinct populations. 



A study of age and growth of Pacific hake is in the final 

 stages. Growth rates have been estimated from data on 

 lengths and ages of the fish. A method of calculating growth 

 from readings of otoliths is being developed. 



FIGURE 47.— Technician preparing density gradients {or ultra- 

 centriiugation to isolate enzymes. 



FLOATING AQUACULTURE LABORATORY 



Because aquaculture has a great potential for increasing 

 food supplies in the future, the Biological Laboratory is de- 

 veloping plans for a major research program. Our floating 

 laboratory, the Brown Bear, will be useful in these studies. 

 The laboi'atory circulates fresh and salt water which can 

 be modified by aeration, filtration, temperature control, and 

 ultraviolet sterilization. The Broum Bear also has trays 

 and tanks for culture of fish or shellfish (fig. 48) and ex- 

 cellent facilities for study of water chemistry (fig. 49). 



One proposed phase of aquaculture would place a marine 

 fish and shellfish laboratory in salt water adjacent to a therm- 

 al nuclear power plant and a primary sewage treatment 

 plant. This situation would take advantage of nutrients 

 and heated water that are liyproducts of the plants. Basic 

 food organisms would be nourished by the chemical nutrients, 

 and cold waters could be warmed to improve the growth and 

 production of fish and shellfish. 



36 



