Effects of water temperature on growth of razorback sucker larvae

I conducted laboratory experiments and fit a response surface regression model to evaluate growth of endangered razorback sucker (Xyrauchen texanus) tip to 37 days post-hatch. Fish growth at ad libitum ration was positively related to water temperature, and larvae reared at 25.5 degrees C grew about twice as fast in length and 4 times as fast in weight as those at 16.5 degrees C. Growth was intermediate at 19.5 degrees C and 22.5 degrees C. Time required for razorback sticker larvae to exceed 25 mm total length (TL), a potentially important threshold for reduced predation, was 30 days (post-hatch) at 25.5 degrees C, 33 days at 22.5 degrees C, 36 days at 19.5 degrees C, and 41 days at 16.5 degrees C. Time to exceed 25 mm TL increased to 52 days tinder a low growth rate of 0.29 mm.d(-1). Faster growth rates could reduce the time that razorback sucker larvae are vulnerable to predation by abundant and co-occurring small-bodied fish and invertebrate predators in nursery areas. Growth of razorback sticker larvae could be enhanced if flow re-regulation at Flaming Gorge Dam and downstream levee removal restored connections between the Green River and its floodplain and increased availability of warm and productive wetlands.