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Mammoth Dam
Westmoreland County
May 2010
Survey Gear: Night Electrofishing and Pennsylvania Style Trap Nets

Mammoth Dam is a 25 acre impoundment located within Mammoth Park in Mount Pleasant Township, Westmoreland County. The lake is owned and operated by Westmoreland County and is managed for fishing by the Pennsylvania Fish and Boat Commission. The lake is easily accessible from three public entrance points. Boating is not permitted on the lake, but 100% of the shore is fishable. With an average depth of only about 3 feet, the lake has faced serious sedimentation problems and heavy vegetation growth, but still offers coldwater fishing opportunities through seasonal stockings of rainbow, brown and golden rainbow trout.

Mammoth Dam also offers year-round fishing, including ice fishing, for other species as well. A previous survey conducted in 1997 revealed the lake contained an abundant population of bluegill and white crappie, along with a moderate brown bullhead population. A dense population of largemouth bass was also present, but the number of legal-size bass made up only a small percentage of the total. For this reason, Big Bass regulations were applied to Mammoth Dam in 1999.

The lake was surveyed in May 2010 by Area 8 fisheries management personnel from Somerset, PA using night flat-bottom boat electrofishing and Pennsylvania style trap nets. The reason for the survey was to assess the lake’s warmwater and coolwater fish populations, along with updating management strategies for the lake.

Night electrofishing for 35 minutes yielded 113 largemouth bass ranging in size from 6 to 17 inches, with the majority of the fish being 12 to 14 inches. A substantial increase in the number of bass collected over 12 inches was observed after comparing results to the 1997 survey. From the 1997 survey, only 6% of largemouth sampled were 12 inches or greater, and none were collected over 15 inches. In the 2010 survey, 79% of the sample was over 12 inches, and 15% were over 15 inches, suggesting the Big Bass regulations have been successful in increasing density of larger bass at Mammoth Dam (Figure 1).

Largemouth bass

Figure 1

The trap netting component of the survey resulted in surprisingly low catches. Numerous bluegills were spotted during night electrofishing, including some nice size ones. However, only 16 bluegill were collected in trap nets this year; while the survey in 1997 yielded a catch of 555 bluegill. Results in 2010 were similarly low for other panfish, including black and white crappie. The reason for this isn’t believed to be a substantially reduced panfish population, but rather a consequence of the deployment of the trap nets over excessively heavy vegetation. Heavy aquatic vegetation is known to cause reduced fish capture with trap nets.

Other species collected in the trap nets included yellow perch, pumpkinseed, brown bullhead, yellow bullhead, rainbow trout, brown trout, common carp, golden shiner and white sucker (Table 1).

Table 1. Fish species captured from night electrofishing and trap netting at Mammoth Dam,
Westmoreland County, during May, 2010.
Fish Species Number Collected Size Range (inches) Additional Comments
Largemouth Bass 115 6-17 in. 79% over 12 inches
15% over 15 inches
White Crappie 12 8-13 in. 100% over 7 inches
92% over 9 inches
Black Crappie 32 5-9 in. 81% over 7 inches
3% over 9 inches
Bluegill 16 3-9 in. 6% over 7 inches
Yellow perch 4 7-10 in. 75% over 9 inches
Pumpkinseed 1 6 in. 0% over 7 inches
Brown Bullhead 10 9-12 in. -
Yellow Bullhead 3 9 in -
Rainbow Trout 3 Not measured -
Brown Trout 1 Not measured -
Common Carp 3 Not measured -
Golden Shiner 1 Not measured -
White Sucker 39 Not measured -
Overall, Mammoth Dam provides opportunities for anglers to catch good numbers and sizes of largemouth bass. Stocked trout also provide fishing opportunities during the cooler months. Although we caught few panfish in our trap nets, samples included very nice sized crappie and we observed numerous bluegills during our night electrofishing runs. Due to excessive amounts of vegetation impacting our trap net catch and impacting fishing opportunities in the lake we will return in August to conduct an aquatic vegetation survey. We will then work with the Westmoreland County Parks and Recreation Office to develop and implement a vegetation control strategy for the lake to improve fishing opportunities and fish populations.
— Ryan Fuller and Mike Depew, Fisheries Management Area 8

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