Difference between revisions of "Green Sunfish Page"
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Colorado River discharge and temperature measured at Lees Ferry from fall 2015 to fall 2016. | Colorado River discharge and temperature measured at Lees Ferry from fall 2015 to fall 2016. | ||
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2016 HFE at 38,000 cfs | 2016 HFE at 38,000 cfs | ||
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*[https://goo.gl/photos/e9fYmrEWVeEBujiA6 Photos of the 2015 green sunfish treatment] | *[https://goo.gl/photos/e9fYmrEWVeEBujiA6 Photos of the 2015 green sunfish treatment] | ||
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Survival, growth, and condition factor were higher for fed than starved fish at both temperatures. Survival, growth, and condition factor were highest for fed fish at 9C, intermediate for both fed and unfed fish at 4C, and lowest for 9C starved fish. Large fish had similar survival to small fish when fed, but large fish had higher survival than small fish when they were starved. Activity levels during the experiment were highest for fed fish held at 9C. Activity levels were similar for unfed fish at 9C and fed fish at 4C; unfed fish at 4C had the lowest activity level. Fall and spring bluegill collected from 10 lakes in Illinois indicated that the pattern of overwinter mortality is highly variable among systems. We propose that winter food availability and winter severity interact to determine the extent of size-specific mortality experienced by age-0 bluegill in natural systems. <br> | Survival, growth, and condition factor were higher for fed than starved fish at both temperatures. Survival, growth, and condition factor were highest for fed fish at 9C, intermediate for both fed and unfed fish at 4C, and lowest for 9C starved fish. Large fish had similar survival to small fish when fed, but large fish had higher survival than small fish when they were starved. Activity levels during the experiment were highest for fed fish held at 9C. Activity levels were similar for unfed fish at 9C and fed fish at 4C; unfed fish at 4C had the lowest activity level. Fall and spring bluegill collected from 10 lakes in Illinois indicated that the pattern of overwinter mortality is highly variable among systems. We propose that winter food availability and winter severity interact to determine the extent of size-specific mortality experienced by age-0 bluegill in natural systems. <br> | ||
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Revision as of 17:15, 21 March 2017
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Green Sunfish (Lepomis cyanellus)Description: Native to the Great Lakes, Hudson Bay and the Mississippi River basin. Introduced into Arizona in 1926. Large mouth with blue-green striations on the cheeks. Opercle flap is black with reddish or orange border. Bodies olive-green in color, dark vertical bars are faintly seen on sides. Pectoral fin short and rounded. Caudal fin and lower fin margins are white or yellowish with dusky spots at rear of dorsal and anal fins. Length: 3 to 12 inches. Weight: 3 ounces to 1 pound 8 ounces. May live to nine years. Location and Habitat: Found in most seasonally warm water lakes and streams in Arizona. Prefer lakes with rocky substrate and piles of rubble, but can be found in slow moving rivers and riverine backwaters. Green sunfish have been found at a wide range of stream gradients, varying from 0.2 to 5.7 m/km; however, they are most abundant at lower (<2 m/km) gradients. They prefer small to medium-sized (<30 m width) streams.[1] Being native to the Great Lakes and Mississippi River Basin, green sunfish are well suited to tolerate long periods of cold water. Temperature: Being native to the Great Lakes and Mississippi River Basin, green sunfish are well suited to tolerate long periods of cold water. The summertime temperature preference for adult green sunfish is 28.2° C and, when possible, they avoid temperatures above 31° C or below 26° C. Growth and food conversion efficiency increase as temperature increases from 13.2 to 28° C. Optimal temperatures for fry range from 18 to 26° C. The range of tolerance for bluegill fry is 10 to 36° C, and it is assumed that green sunfish fry tolerances are similar. Temperature requirements for juveniles are assumed to be the same as those for adults.[2] 2015-2016 temperatures in the mainstem ranged from 8.0-15.5 C between Lees Ferry and the Little Colorado River. 2015-2016 temperatures in the Little Colorado River ranged from 10.0-28.0 C and are within the temperature tolerances of green sunfish spawning and growth. Turbidity and Dissolved Oxygen: Green sunfish tolerate greater turbidity and lower dissolved oxygen than other sunfish.[3] Moderate (25-100 JTU) turbidities correlated with high species abundance are optimum.[4] Ventilation rates were not affected by bentonite clay suspensions below 2,125 FTU at 5 C, 1,012 FTU at 15 C, and 898 FTU at 25 C. At turbidity levels exceeding 1,012 FTU at 15 C and 898 FTU at 25 C ventilation rates increased 50-70%. Oxygen consumption rates were not affected by turbid suspensions of up to 3,500 FTU at any of the four temperatures.[5] Salinity: Green sunfish have preferred salinity tolerances <0.36% and will not tolerate salinity >0.56%.[6] The Little Colorado River has a naturally high salinity at baseflow ranging from 0.22% - 0.36%.[7] Reproduction: Optimal temperature for spawning and subsequent development ranges from 20 to 27° C. Spawning will not occur below 19° C or above 31° C.[8] Males build nests in shallow pools over gravel, sand or bedrock. The nests are usually within a couple feet of each other. The male guards the nest and hatched fry. Males constantly show defensive displays and fight with other males who come too close. It is thought that green sunfish may produce the same number of eggs as bluegill, which is roughly 50,000 eggs per female. It takes normally 1 to 2 days for the eggs to hatch and another 5 to 7 days of protection from the male until the fry become independent. Green sunfish can spawn up to every 8 to 10 days during the spawning season.[9] Food: Green sunfish will eat anything they can catch and swallow. Aquatic and terrestrial insects and invertebrates are the most common food items. Small crayfish, humpback chub, and frogs are all in danger when green sunfish are present. Young life stages of chub do not persist in streams occupied by Green Sunfish. No recruitment of young-of-year Gila Chub (Gila intermedia) occurred in the presence of sunfish in Sabino Creek, Arizona (Dudley and Matter, 2000). Risk: Green sunfish may temporarily be displaced into colder more unfavorable environments where survival might be lower, but the fish that do survive will seek out warm backwaters and tributaries after moving downstream. An upstream source that continues to allow new individuals to disperse downstream and colonize tributaries, when they are not in flood stage, greatly increases the likelihood of sunfish establishment in tributaries of the CRe. If no action is taken, there is a high risk of sunfish spreading downstream and becoming established in and near other tributaries, primarily the Little Colorado River, where negative impacts to the endangered humpback chub will occur. (Green Sunfish Risk Assessment) |
Online training |
Fish Species of the Colorado River in Lower Glen Canyon and Grand Canyon |
Fish photos, information, and maps |
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