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Effects of Freshwater Influx; Maybe Not So Bad After All

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On: Fri, Jul 31, 2015 at 10:57AM | By: Captain Ron Kowalyk

We don’t wanta make the rain seem like a bad thing, especially after the heat wave we’ve endured over the past few weeks. All streams lead to the sea, but in our case fish have gotta navigate the rivers and estuaries so vital to our inshore fishery.

We’re blessed with a whole menagerie of game fish that tolerate brackish water that verges on sweet water at times. That gives our skiff fisherman, canoe paddlers, and kayakers miles and miles of access to snook, tarpon, redfish, bass, and cichlids—great stuff! A strong outflow of rainwater will carry masses of forage critters—small fishes, insects, all manner of larvae and other creepy crawlers. This can be a nutrient-rich soup in a torrential flow of fresh water cascading down to our estuaries but needs some special attention. There an old saying among bass and trout fisherman that “there ain't much fishin’ when the water’s so high on the log”; in other words, the flow, turbidity, and depth slow the bite. Add the sudden temperature and salinity changes and you’ve got a number of factors working against you.

Addressing these issues requires a bit of careful observation, testing and planning. The other day we were checking out the Estero River after it cleared up, but there was no bite in the high fast-moving upstream waters. We move down to the bay just at the mouth of the river and found a nice bite on the adjacent flats; go figure. We put our heads together and after a careful perusal of the conditions on the flats and channels near the river mouth realized that the influx of sweet, cooler water had perked up the earlier torpified speckled trout. This was particularly noticeable on the outgoing tide. Our surmise was that the natural mixing effect of the earlier incoming tide and the cooling effect of the freshwater influx perked up the game fish as well as the forge critters. This effect was noticeable pretty much throughout the bay. The less dense, cooler rainwater was mixed with the very warm denser saltwater, thus producing a comfort zone throughout the water column. A reduction of water temperature of only a few degrees can be critical, especially in the shallow bays and on the flats.

These observations can save a day on the water, keep an eye on the temperature feature on you depth finder and follow the cooling trend. Snook, redfish, trout and tarpon are less affected by salinity and more influenced by water temperature and oxygenation. Cooler rainwater agitated by wind and tides will carry a refreshing shot of oxygen and a relief from the stress of overheating. Consider that overcast cloudy conditions of rainy days and the influx of cooler water combined with the mixing effects of tides and wind, should put our finny friends back on a feed.

Capt. Ron Kowalyk: 239-267-9312


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