Mark and recovery estimates of fish populations in three heated reservoirs of Texas.

Estimates of fish populations in Lake Bastrop, Lake Nasworthy and North Lake, Texas were made by mark and recapture techniques. The lakes were divided into four, seven and three strata, respectively. Fish capture in each stratum were finclipped with a different combination of marks. Equal sampling was conducted in each stratum within each lake. Hoop nets, trap nets, gill nets (not used in North Lake) and electro-fishing (only used in Lake Bastrop) were used to collect fish. Six major basic assumptions were discussed in reference to their effect on the population estimates. The methods of Schnabel and Schumacher-Eschmeyer were used to obtain a good estimate as shown by Cooper and Lagler's laboratory studies. The estimate from the Schumacher-Eschmeyer method was more variable than that from the Schnabel method when nonrandom distribution of the fish or lack of recaptures in some sampling periods occurred during the study. Estimates by group of days were always below daily estimates for both methods. The estimates of number of fish per acre which were considered the most accurate were: black bullhead 4.1, yellow bullhead 2.7, green sunfish 7.0, bluegill 337.5, longear sunfish 43.9, redear sunfish 135.5 and largemouth bass 7.8 in Lake Bastrop; carp 26.7, golden shiner 6.1, river carpsucker 0.3, black bullhead 1.0, channel catfish 4.0, flathead catfish 0.6, white bass 0.8, bluegill 924.4, longear sunfish 14.5, redear sunfish 89.2, largemouth bass 2.3 and white crappie 115.8 in Lake Nasworthy; channel catfish 1.8, bluegill 14.0, longear sunfish 0.3 and redear sunfish 0.7 in North Lake. Recapture rate increased with size for white crappie at Lake Nasworthy. Recaptures in strata other than the stratum where marked indicated much movement between strata for carp, golden shiner, white bass and white crappie in Lake Nasworthy.