Campaign Update: Finding Fish Where Fish are not Supposed to Be...
NFC has been working at Cheesecake Brook in Newton, Massachusetts, since last fall. This heavily altered suburban/urban stream has been straightened, dug down, walled in, and buried. Just before joining the fish-rich Charles River, the stream flows over a wide shallow sloping cement slab that is said to block fish from gaining access to the stream from the river.
Prior to NFC digging in, the only fish that had been reported from Cheesecake Brook was a lone what appeared to be a medium size pond comet, likely the result of a released aquarium pet. In order to understand what could be in the stream if there were passage from the Charles River, NFC seined the large pool below the cement slab and found several fish species.
A month or so later, MA NFC board member Jeff Moore was able to trap a single juvenile native white sucker from upstream of the slab. This was notable as while the stream is a bit small for adult suckers, the river is full of them and they tend to be stream spawners. This was an indication that while not definitive, some fish may be able to get past the cement slab at certain water levels.
In late August, NFC was joined by MassWildlife to e-fish the stream to see what they could turn up. The group surveyed both below and above the cement slab to help understand what species of fish are where, and what impact the slab is having on fish passage. The water temperature was roughly 68F in the Charles River while the stream was an oddly cool 59F degrees.
The group e-fished the large pool immediately below the cement slab as well as the riffle between there and the river. They sampled the long deep pool above the cement slab, along with one section of shallow moving water upstream of Crafts Street.
Per Adam Kautza of MassWildlife, the stream had very high conductivity. This is often associated with high salt content. NFC will come back with our DO meter to try to get a better understanding of where conductivity is highest and lowest and why.
Downstream of the cement slab the group encountered American eel, redbreast sunfish, pumpkinseed sunfish, yellow bullhead, and white sucker. All except yellow bullhead are native to the Charles River system. But it is what they found upstream that really changed the game and what we believed the stream was capable of supporting…
Immediately upstream of the cement slab, the group captured 7 juvenile [common?] carp, 5 juvenile white sucker, and 2 American eel. All except carp are native to the Charles River system. Upstream of Crafts Street, they encountered 4 American eel up to 15", 7 juvenile carp, and 1 white sucker. All except carp are native to the Charles River system.
The difference in regard to species found upstream and downstream of the cement slab was the two sunfish species which were present downstream but not detected upstream. While certainly not definitive in regard to presence/absence, it's possible that their body structure - tall and slim, and the fact that they use their dorsal and anal fins to propel them through the water rather than their tail, makes it harder for sunfish to navigate the slab regardless of water level.
As expected, a section where grass clods have fallen into the stream from above the stone wall proved to be a good area for fish. In addition to adding sinuosity and increasing flow, these grass banks and islands provide important cover for fish. While there was previously talk of removing these dirt/grass structures, NFC will try to discourage it as we believe they are critical in regard to supporting fish in a stream with very limited natural banks due to being walled in.
“While it’s possible that someone released suckers and carp into the stream, it’s just as likely that they moved there from the river...”
The presence of eel, carp, and sucker upstream of the cement slab indicates that fish are utilizing the stream. It also implies that there is likely at least some level of movement between the river and stream at certain times of year and water levels. While it’s possible that someone released suckers and carp into the stream, it’s just as likely that they moved there from the river. As for eel, while their presence in varying sizes is a great sign in regard to water quality, their ability to navigate the slab was never in question.
It's also important to note that eel are catadromous, or freshwater fish that spawn in the ocean, and carp, especially common carp, are known to inhabit brackish water in estuary systems. While to a much lesser degree than carp, white suckers are found in brackish water occasionally as well. These species would be naturally more tolerant of high salinity than sunfish and other freshwater fish species.
This exercise proved that when it comes to finding fish, nothing works as well as e-fishing. It's really good at moving fish that cannot easily be trapped or seined. This is especially true in regard to shallow and fast runs, as well as areas with in-stream and bank structure. We hope to be able to return to do some more e-fishing upstream of where we did last time.
Special thanks to Adam Kautza from MassWildlife for taking time to e-fish with us, MassWildlife volunteer Brian Means, MA NFC board member Jeff Moore for his coordination and assistance, and Emilia Dick Fiora del Fabro from CRWA for showing up on very short notice.
