The low abundance and small size structure likely limit current pumpkinseed fishery in Lake Enemy Swim , but that may change in future years . If you fish Lake Enemy Swim in northeast South Dakota and catch a pumpkinseed , please take some time to marvel at their colorful splendor . You will not be disappointed . •
the current ( 2023 ) Enemy Swim pumpkinseed population characteristics and examine how the parameters may have changed over the last 25 years ( 1999-2023 ).
Population Decline
In 2023 , pumpkinseeds were collected for age assessment in trap nets during May in conjunction with ongoing GFP bluegill research and during June as part of the annual GFP fish community survey work on Enemy Swim Lake . Previous GFP fish community surveys were annually completed at approximately the same time of year from 1999-2022 . All collected pumpkinseeds were measured for length and weight , and in 2023 , their otoliths were removed to estimate their age .
Otoliths are hard calcium carbonate structures in the fish head , used to help with balance and hearing . In winter , when fish growth slows , a ring forms ( annulus ) on the otolith , and by counting the number of annuli present , their age can be estimated .
The pumpkinseed population in Enemy Swim Lake has been declining since 2001 and was found to be of low abundance in 2023 . In 2001 , trap nets caught an average of 4.0 pumpkinseeds per net , and in 2023 , only 1.3 fish per net were collected . Although not plentiful , their abundance is similar to that of other populations found outside their native range . For example , in the Nebraska Sandhills ( outside the native range ), average trap net catches were similar to Lake Enemy Swim , with values
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Page 22 , Dakota Country , September 2024 ranging from 0.6 to 7.5 fish per net . Conversely , the abundance in Lake Enemy Swim is substantially less than populations within their native range . In Michigan and Wisconsin , which are within the native range , trap net catches exceeding 30 fish per net are common .
Habitat Issues
There are several possible reasons for the low abundance of pumpkinseeds in Enemy Swim . One possibility , as I already alluded to , is that Enemy Swim is outside the native range and may lack a necessary component ( e . g ., food resource ) for pumpkinseeds to prosper . The high abundance of bluegills in Enemy Swim could negatively influence pumpkinseed abundance . Where pumpkinseeds co-exist with bluegills , their abundance is usually low . This is because competition for available food resources between juvenile bluegills and pumpkinseeds can be high and may limit pumpkinseed survival to adults . It ’ s also possible that predator fish ( walleyes , northern pike ) present are eating pumpkinseeds , limiting their abundance .
Like abundance , size structure of the pumpkinseed population has declined since 2005 . Before 2005 , more than 70 percent of sampled fish were larger than 6 inches . In recent years , the percentage of fish collected exceeding 6 inches has ranged from 4 % - 38 %. No pumpkinseeds exceeding 8 inches were caught in 2023 , and none have been sampled
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BAIT -- Wilton ( minnows , worms & leeches ) // Wing ( worms & leeches ) since 2016 . Eric Weimer caught few fish larger than 8 inches during his 1998-2003 study .
It may be difficult for pumpkinseeds to reach 8 inches outside their native range . Similarly , no 8-inch fish were caught in the Nebraska Sandhills lakes during 1998-1999 . Angler harvest may contribute to limited numbers of fish reaching 8 inches . Bluegill fishing is popular on Enemy Swim , and many anglers likely include larger pumpkinseeds ( 7 inches-plus ) that they catch in their harvest .
Slow Growth
The observed declining size structure may be related to a decrease in growth . In 2003 , pumpkinseeds grew to 6 inches in 3 years , and in 2023 , 4 years were required to attain 6 inches . Although growth has slowed in Enemy Swim , it ’ s similar to that of other populations found across North America and Europe . Reduced growth observed in 2023 is likely related to the high abundance of bluegills currently found in Enemy Swim and possibly limited availability of food resources ( e . g ., snails ).
Zebra mussels were found in Enemy Swim in 2022 . The presence of zebra mussels could increase pumpkinseed growth and abundance . In several Canadian lakes where pumpkinseeds and zebra mussels occurred together , 68 percent of the pumpkinseed diet was zebra mussels . Thus , zebra mussels may provide a new and abundant food source , which could lead to increased growth . Also , because of the likely increase in water clarity with zebra mussels , submerged vegetation may increase , providing additional nursery habitat for juvenile pumpkinseeds . In Oneida Lake , New York , pumpkinseed abundance increased once zebra mussels were present . We ’ re uncertain what impacts zebra mussels will have following zebra mussel introductions have been unclear .
The low abundance and small size structure likely limit current pumpkinseed fishery in Lake Enemy Swim , but that may change in future years . If you fish Lake Enemy Swim in northeast South Dakota and catch a pumpkinseed , please take some time to marvel at their colorful splendor . You will not be disappointed . •
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