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Effects of Food and Cover on Numbers of Apache and Brown Trout Establishing Residency in Artificial Stream Channels
Author(s) -
Mesick Carl F.
Publication year - 1988
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1988)117<0421:eofaco>2.3.co;2
Subject(s) - brown trout , trout , salmo , biology , fishery , stocking , zoology , ecology , fish <actinopterygii>
The importance of food and cover in controlling the abundance of Apache trout Oncorhynchus apache (formerly Salmo apache ) and brown trout Salmo trutta was tested in indoor artificial stream channels that permitted emigration. Under different levels of food and cover, Apache trout, 7.0–21.5 cm standard length (SL), and brown trout, 6.3–21.1 cm SL, were placed in separate but identical channels from which they could emigrate at will. After 4–7 d, when emigration had ceased for 24 h, the fish remaining in the channels were counted. Apache trout of all sizes tested and brown trout at least 17 cm in length required overhead cover, in the form of concrete blocks providing a dark area, to maintain residency. Object cover, in the form of concrete blocks providing only visual screening, slightly increased numbers of 6.3–21.1‐cm brown trout remaining in the channels but did not affect the numbers of Apache trout. The emigration of both species in response to a lack of food was relatively slow for the small fish, and larger fish showed no response at all. Only a few Apache trout less than 11.0 cm SL emigrated after being starved for 10 d, and their numbers did not increase when food (brine shrimp Artemia sp. and trout pellets) was increased from one feeding per day (30 g/d) to four feedings per day (total of 80 g/d). Forty‐one to 73 d of starvation were required before the numbers of resident Apache trout, 12.0–13.9 cm SL, were reduced. Apache trout at least 14 cm in length showed no change in the number of residents whether they were fed or starved for 73 d. Brown trout of all sizes showed no response to starvation or increased food under the same conditions used during Apache trout tests. Several months of starvation were required before the smallest brown trout emigrated; emigration occurred after the condition factor of these fish, 10 2 (weight, g)/(standard length, cm) 3 , dropped below a range of 1.25–1.37.