Fish, Temperature, and Oxygen at the Wissahickon Park

I went fishing at the Wissahickon on July 19th - this past Tuesday. My primary goal was the good old Carp, considering that there are good amounts of Carp in the creek. I went out really early, and I arrived at the park 6:40 a.m. Pulled my rods out, chummed the water at the moment, and landed a 9lb Common Carp almost after three hours of waiting. The reason for the wait was simple: I noticed that the levels of water at the creek lowered, and the vegetation increased. The water was not even flowing past the 2 little dams at the entrance of the Park next to the Wissahickon Transfer Center. Of course the water wasn't stagnant; However, it's common that fish may seek other locations to stay at when water levels drop (specially at summer time). It's common to see fish moving from location to location due to Oxygen levels in the water - fish will prefer locations that I richer in oxygen. Temperature is also another factor - this Tuesday was extremelly hot: 90-95F. When the water temperature rises dramatically, it certainly influences the eating behaviors of certain species of fish.

Therefore, I found fundamental to do an oxygen and temperature review, specially using the Wissahickon as an example.

First, we should divide the different species of fish in the Wissahickon according to their temperature preferences. I'll divide the temperature in three ranges:

1. Coldwater (50-60)

Rainbow Trout; Brown Trout; Palominos.

2. Coolwater (60-70)

There are no species in the Wissahickon (that I know) that are classified in Coolwater.

3. Warmwater (70-80)

Largemouth Bass; Bluegill; Rock Bass; Redbreast Sunfish; Channel Catfish; Common Carp and variations.

Before continuing, we should notice three things: (1) Trouts are only present in the creek because they are stocked by the Fish and Boat Commission. Therefore, if they did not stock trout, the creek would basically have only Warmwater fish. (2) Carps prefer temperatures that range from 73F to 86F. This means that Carp tend to bite less if the water temperature is ABOVE 86F. (3) Even though those are the species preferenced water temperature, it doesn't mean they will be found only in that temperature range. They move mostly according to food: fish will be present where food is more plentful.

The reason trout can actually survive high temperatures at the Wissahickon creek on summer time is the fact that Coldwater fish are limited to waters that provide refuge for cold, oxygenated water on summer time. Therefore, it does make sense that all trout anglers usually fish for trout deeper when it's hot, and usually right under dams - where water is rich in oxygen due to circulation; food comes downstream with flow; and water is cooler due to convection and surface area of circulating water.

Warmwater fish, on the other hand, are species that walk around their respective waters the whole summer - when temperatures are high.

The Carp that I landed (the 9lb one) was caught at a very shallow portion of the creek, which kinds of prove the fact that they will be where food is more plentiful, despite temperature conditions. After all, fish are clearly opportunists, and they take advantage of any kind of bait when they have a chance to eat it.

Also, the same day that I went fishing for Carp, I switched spots to try for different kinds of fish. I went to a spot further inside the creek, after crossing a red bridge. There, the water had a much stronger current, and it was perfect for casting lures. I ended there with one Rock Bass, 4 Largemouth Bass (not big, though), and one small Brown Trout caught on a trout magnet at the bottom. Therefore, this is clear evidence to support the theory that temperature is an extremelly important factor to determine the activeness of a certain species of fish.

Ample dissolved oxygen MUST be present in the water fish live at. To balance with air, water absorbs oxygen in contact of air. Therefore, a similar experience happens when water is moving (e.g. Dam): just as the temperature drops because of convection and area surface of the flowing water, oxygen is absorbed in bigger quantities due to the surface and flow of water. Also, oxygen can be produced by aquatic plants. Notice that it's not EVERY plant in the water that produces oxygen, though. Just because the plant is in the water, it doesn't make it aquatic. Basically, certain species tolerate lower oxygen levels than other fish(e.g. A Bullhead tolerates much less oxygen than a Trout), and this factor determines the location of fish in certain waters.

In reality, there are three factors that determines the amount and size of fish: the water temperature, the dissolved oxygen level, and fertility.

Maybe one day I'll do a post on fertility. For now, that's all.

I hope this was informative for your guys.

Best luck for all of us.

Long Days and Pleasant Nights.

Leo S.