摘要:

Limnological conditions were studied in eight lakes ranging in area from 20 to 73 ha. and in mean depth from 2.4 to 7.0 m. Summer thermal stratification occurred in five, while three were subject to mixing throughout by winds. August mean water temperatures varied from 14.9° to 22.0 °C. Lowest mean dissolved-oxygen content was 71 per cent saturation although pronounced summer hypolimnal deficits developed in the stratified lakes. The lakes lie in a wooded area of poor soils, underlaid with granite rocks. Bicarbonate content ranged from 5.1 to 11.1 mg./l. Phosphate P was usually < 10 mg./cu. m., even in hypolimnia. Total P averaged about 15 mg./cu. m. with extremes of 5 and 34 mg. Allochthonous humic extractives coloured the waters in varying degree (5 to 59 p.p.m.). Adverse edaphic factors conditioned a low level of productivity. Desmids were qualitatively prominent in the plankton. Rooted aquatic vegetation was generally a minor feature. Dominant bottom organisms wereHyalella,Amnicolaand sphaeriids in shallow andChaoborusand chironomid larvae in deeper water. Fish fauna consisted of 18 species; at least speckled trout, eel, lake chub and banded killifish were common to all lakes.Yields of speckled trout to anglers were assessed by creel censuses. Rate of capture averaged 0.3 per rod-hour over a seven-year period. Average annual yield was 0.65 kg./ha. Trout in their third (22 cm., 130 g.) and fourth (29 cm., 263 g.) years of age made up 85 per cent of catches. Growth rates were similar in all lakes. Introduced trout contributed little unless planted at angling size and cropped within a year. The supply of young native trout was apparently sufficient to utilize full trout-producing capacities of these lakes.

ISSN:0706-652X    

DOI:10.1139/f50-028

出版商:NRC Research Press    

年代:1952

数据来源: NRC