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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Revision as of 15:57, 4 October 2016
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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) |
 Rainbow Trout |
 Fish Species of the Colorado River in Lower Glen Canyon and Grand Canyon |
 Brown Trout |
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