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Green sunfish Green sunfish were ubiquitous and the most abundant fish electrofished from backwaters. For the six sampling periods, an average of 57% (17-95% range) of the backwaters sampled by boat and 94% (83-100% range) of those sampled by barge yielded green sunfish. Distribution was fairly even throughout backwaters of the Grand Valley, although especially high densities were found in backwaters upstream of Loma between rm 152 and 156. The scarcity of green sunfish in the Loma-to-Westwater reach was largely due to the scarcity of backwaters there, and like largemouth bass, consistently occurred in only three backwaters within that reach. However, in two of these backwaters (rm 146-148), there were very high densities (Fig. 2). For the entire target area, total catch was relatively constant among the six sampling periods, and ranged from 1,516 (fall 1999) to 2,226 (Spring 2000). Catch per backwater was highest in fall of 1999 and was essentially constant during the last three sampling periods (Fig. 3). Captures using the barge accounted for 91% of the total three-year catch, or 72-98% of the catch in each of the six capture periods. Total length of captured green sunfish ranged. from 22 to 198 mm. Length frequency histograms suggested more temporal variation in size structure of the reach- wide green sunfish population compared with the largemouth bass population (Fig. 5). In spring of 1999, 57% of the green sunfish were smaller than 50 mm, but by fall many of these had evidently either grown in length or not survived: only 24% were smaller than 50 mm and 56% were 50-90 mm long. However, in spring of 2000, the percentage of very small green, sunfish (<50 mm) had increased (45%), suggesting a new year class had entered the population. Again, by fall of 2000, sunfish were generally larger and only 8% were < 50 mm long. Size structure of the green sunfish population changed very little during the last three sampling efforts (Fig. 5), and there was no evidence of additional cohorts produced. An overall length frequency from the combined lengths of the six sampling periods (N = 8,870) portrayed a population consisting of 23% fish <50 mm, 56% fish 50-99 mm, 20% fish 100-149 mm, and 1% fish 150-199 mm long. 12