Fishing suffers from saltier seas
By David Sikes
Tuesday, August 4, 2009

CORPUS CHRISTI — The most visible effect of the drought on Coastal Bend bays has been the southward migration of fishing guides and other anglers from Rockport and Aransas Pass.
The early morning ferries at Port Aransas have been crowded with bay boats, guides and anglers who have experienced difficult trout fishing in their home waters of Aransas Bay and northward. The upside is that redfish and black drum fishing has been good, guides said. But guides and anglers who target summer trout are enjoying greater success south of the JFK Causeway.
Rockport guide Jay Watkins said this is the worst trout fishing he has seen since the aftermath of the last fish-killing freeze in 1989. Like many upper Coastal Bend guides, he’s spending much of his time in Laguna Madre and Baffin Bay.
Rockport guides generally blame an extreme low tide, near 90-degree bay temperatures and unseasonably high salinities. Texas Parks & Wildlife fisheries biologist Karen Meador hesitates to speculate on why fish won’t bite, but she can attest to the extreme conditions.
Usually this time of year the Coastal Bend’s northern bays, which are fed by creeks and rivers, are not nearly as salty as the Gulf of Mexico, which is around 35 parts per thousand.
Just this past week the salinity of Aransas Bay was greater than 40 ppt for the first time since 1997. It was 41.5 ppt.
The average salinity around Rockport now is 37 ppt, compared with the seasonal norm of about 25 ppt, Meador said. This is a significant difference, she added.
But it’s not nearly as dramatic as the salinity extremes during the past year or so. The freshwater inflow in late 2007 was substantial, leaving some of the river-fed bays with prolonged single-digit salinities.
“Usually this process is much more gradual,” she said. “I haven’t seen that kind of dramatic one-year fluctuation in 30 years.”
High salinities generally result in poor survival for newly hatched fish. And Rockport bays already were suffering a dip in their trout population. The upside is that last year’s trout spawn was successful and just a few years ago Rockport’s trout population reached a record high. Unfortunately, today’s trout dip puts it at the lowest point since 1986, Meador said.
Several fish kills have been recorded in the Rockport area recently, but small fish kills occur most summers, Meador said. Low levels of dissolved oxygen usually are to blame. Hot, salty water doesn’t hold oxygen well.
This year's fish kills mostly involved water and fish trapped by a falling tide. With high winds and heat, it doesn’t take long for oxygen to deplete and fish to die, Meador said. These die-offs occurred earlier than usual this year, Meador said, which could mean the worst is yet to come.
Under these conditions, upland runoff from a good hard rain could spark an algae bloom, which would further deplete dissolved oxygen in the bays, she said.
Certain submerged vegetation also has had a difficult time surviving in high salinity, Meador said. She has seen a decline in widgeon grass, which could bode poorly for ducks and duck hunters. However, if stock tanks on San Jose Island and elsewhere remain dry, this could play into the hands of duck hunters by concentrating waterfowl in the bays. Teal season starts Sept. 12 and duck season opened last year on Nov. 1. This year’s date hasn’t been announced.
In the Laguna Madre, where fish are accustomed to high salt levels, TPW biologist Kyle Spiller said he’s measuring some extremes. The Laguna Madre has gone from 36 ppt salinity in January to 45 ppt in June and average salinities into the 50s in July. The highest salinity recorded this summer was in Laguna Salada. It was 71 ppt in this finger of Baffin Bay.
High salinity has caused crews at the CPL/CCA Marine Development Center, known as the Flour Bluff Fish Hatchery, to alter operations. They know from experience that hatching and rearing redfish and trout in salinities beyond 45 ppt can limit success. So hatchery biologists are taking measures to allow these tiny fish a longer acclimation period in saltier water at the facility before releasing them.
In the previous wet year, Laguna Madre/Baffin Bay salinities averaged 28 ppt in January, 42 ppt in June and 34 ppt in August.
But again, Laguna Madre fish have evolved to withstand hyper-salinity.
Seagrasses might suffer some, Spiller said. And decaying seagrass could lower the bays’ oxygen level even more. Spiller said if fish spawn in parts of the bay with low oxygen and high salinity, spawning success could suffer.