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Age Analysis Of Fish
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AbstractBowfin (Amia calva) are currently being harvested at high rates in the Mississippi River system for the sale of their roe as a caviar alternative. I evaluated the effect that this industry could have if it expands to include the Great Lakes by describing population characteristics of bowfin from Braddock Bay, Monroe Co., NY. Pectoral fin ray sections were used to age 51 bowfin, and back-calculated length-at-age data were used to fit the Von Bertalanffy growth model. Theoretical maximum length was estimated to be 753 mm TL, the coefficient of growth 0.262, and time at length zero -0.023 years. These values resemble populations described from the upper Mississippi River that grow slower and live longer than populations in the south, and therefore would be affected more by commercial harvesting. Aquaculture could provide an alternative to wild harvest, but no established protocols exist. I attempted captive breeding (tanks and ponds) and tested the acceptance of a commercial and a handmade artificial diet. The 55 bowfin did not respond well to captivity: no breeding was observed and most fish lost weight, but they lost significantly less weight on the handmade artificial diet (P = 0.007). Low-intensity culture of bowfin may not be possible using the conditions I tested while artificial propagation likely will require induction by hormone injection. For many years, wild northern sunfish (Lepomis peltastes) in New York State have been restricted to a single 3.7 km section of lower Tonawanda Creek (LTWC), Erie County near Buffalo, NY, and the species is listed “threatened” in the state. A recovery program has been carried out by NYS Department of Environmental Conservation (NYSDEC) since 2005 to reintroduce the species into historic waters other than lower Tonawanda Creek and to establish new populations in other apparently suitable areas. I sampled on 30 days in 2013 and 2014 by boat and backpack electroshocking in the 3.7 km section of LTWC and at stocking sites within the Niagara River watershed. No pure northern sunfish were captured at any sites. I compared data from 2005, when boat electrofishing of LTWC produced 23 northern sunfish, to my 2013-2014 data to investigate changes in the fish community. From 2005 to 2013 capture of the aggressive, non-native green sunfish (L. cyanellus) increased from 27.7 to 288.3 fish caught per hour of electroshocking (CPUE), a 941% increase. Sensitive species have diminished, including darters and logperches (Etheostoma and Percina spp., respectively; -91% CPUE) and redhorses (Moxostoma spp.; -48% CPUE), and invasive species have increased, such as round goby (Neogobius melanostomus; +200% CPUE). Analysis of similarities (ANOSIM) revealed a significant difference in the LTWC fish community between years (R = 0.806, P = 0.001), and non-metric multidimensional scaling (nMDS) showed a strong separation of fish communities between the two sampling periods. Several suspected hybrid sunfish were collected in 2013 and 2014, and microsatellite DNA analysis confirmed eight bluegill (L. macrochirus) x northern sunfish hybrids, as well as 19 other Lepomis hybrids. It is likely that the fish community of LTWC has changed so it can no longer support northern sunfish. Future stocking efforts should focus on water bodies with suitable habitat conditions and low green sunfish and round goby abundance.