Local anglers and hatchery overseers continue to fear that the ongoing drought has the potential to cause catastrophic losses among the area's fish populations.
Water levels are falling at lower-lying lakes and rivers amid low runoff from the Sierra and triple-digit summer weather. That means water temperatures can rise into the upper 70s and 80s, as opposed to the more normal mid-60s range.
It's not uncommon to see fish that already have gone belly up in the Valley's waterways.
Why? Warm water makes it harder for the fish to take in oxygen.
"It's always a concern," said Larry Hodge, a member of the Fresno Bass Club. "Without the influx of freshwater coming in, the oxygen level gets low and puts the fish in a crucial stage."
The lethal combination has had a major impact on some Northern California fisheries. Last month, the state Department of Fish and Wildlife shipped out all of the rainbow trout from the American River and Nimbus hatcheries near Sacramento to prevent what could have been "extensive -- if not total -- loss of all (the) fish."
They were to be planted around the state as usual, but at an earlier age.
In the San Joaquin River Delta, Hodge has seen anglers weighing in more dead fish at tournaments, "about a handful at each one."
In the central San Joaquin Valley, water at the San Joaquin hatchery in Friant is a little warmer than average, but there's no need to sound the alarm -- at least not yet, according to Greg Kollenborn, the senior hatchery supervisor for Central California.
"Our hatchery is a little warmer than normal but it's in an acceptable range," he said. "At the moment, nothing seems to be an issue of concern. We deal with these issues all the time and make adjustments every year based on water flow, temperature and other criteria."
However, Fish and Wildlife usually starts dealing with this kind of problem in August and September, generally not as soon as late June and early July.
"It's a possibility that our facilities could experience higher temperatures to force us to make changes," Kollenborn said. "We'll thin out inventory to allow for more oxygen to the fish and lower their stress levels."
At the Kern River hatchery, water temperatures are expected to be higher than acceptable and that has the DFW ready to alter planting schedules there, he said.
More trout could be shipped out to colder waters at higher elevations such as Shaver Lake and Courtright Reservoir, Kollenborn said.
"If it continues to be hot like it is right now, it's sure to have an impact," he said. "We haven't experienced a year like this so we're learning as we go. We're constantly having meetings to discuss these things. We just hope to maintain what we got."