Accessibility InfoBronx River Wetlands
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NRG
Aquatic Life
Recreationally Important Species
2002-2003
As part of an effort to evaluate the potential factors that explain the absence of anadromous fish in the river, Lehman College's LaMER gathered data on fish currently in the river system.
Anadromous fish have an important place in the ecology and cultural history of Northeast rivers. These were key species in the fishing industry at one time and remain an important energy source throughout the food chain in the river systesm where they flourish. Further, their populations vary in response to a range of environmental factors and processes, and thus their presence is one indication of ecological health.
Today, populations of anadromous fish are drastically reduced from historic levels and continue to decline in many locations in the Northeast. The effort being made to reverse this trend focuses, in part, on protecting and expanding habitat for these species throughout their potential range.
Recreationally Important Species
- Silversides (Menidia spp.)
- Blue crab (Callinectes sapidus)
- Mendahen (Brevoortia tyrranus)
- Mummichog (Fundulus heteroclitus)
- Striped bass (Morone saxitilis)
- Winter flounder (Pseudopleuronectes americanus)
Summary of All Species Sampled by Lehman College's LaMER
Lehman College/LaMER Fish Sampling Stations
Silverside (Menidia sp.), 2001-2002
Length Frequency Analysis
Weight on Length Regression Analysis
Atlantic Silverside (Menidia menidia), 2002-2003
A sample of 326 fish collected from the estuary during the 2002-2003 sampling season were subjected to both length frequency and regression analysis.
Length Frequency Analysis
The length frequency histogram, with normal curve superimposed indicates two possible cohorts; one cohort in the 2.1 - 5.1 cm size range, and a second in the 4.3 - 9.1 cm size range with the two cohorts overlapping in the 4.1 - 5.1 cm size range.
Weight on Length Regression Analysis
Computing a regression of weight on length for the sample indicated a regression equation of Y = 3.14X - 2.20977, r^2 = 0.8263. This computes to a length weight relationship (W = aL^b) of W = 6.17x10^03L^3.14 indicating isometric growth.
Blue Crab (Callinectes sapidus), 2002-2003
A sample of 230 specimens (109 males and 121 females) were subjected to length frequency analysis based on carapace width.
Length Frequency Analysis
Length frequency analysis indicates three size cohorts with the largest cohort having a size range between 3 and 8 cm, with a peak frequency of 4.5 cm. The second size cohort has a mode at 10 cm, and the third at 14.5 cm. Specimens as large as 19.5 cm have been taken. Males and females in breeding color enter the estuary, and it is clear from the size distribution that the estuary serves as a spawning and nursery ground for this species.
Length Frequency Analysis — Males
Separation by sex shows that for the 109 males examined, the same three size cohorts found for the whole population, still is found.
Length Frequency Analysis — Females
For the 121 females examined, the same three size cohorts can still be observed, however, the size frequency is dominated by only the first two cohorts (4-8 cm, and 9-12 cm).
Mendahen (Brevoortia tyrranus), 2002-2003
During collecting season, so-called "peanut bunker" entered the estuary to feed. A representative school of 242 were collected by push net at our Lafayette Avenue site, and subjected to length frequency and regression analysis.
Length Frequency Analysis
The histogram with normal curve superimposed indicates essentially a single dominant cohort of size range 2.1 - 4.1 cm with a few fish representing a second (4.4 - 5.3 cm) and a third (6.5 - 6.9 cm) cohort probably spawned earlier in the season than the first dominant cohort.
Weight on Length Regression Analysis
Computing a regression of weight on length for the sample indicated a regression equation of Y = 3.39X - 2.08175, r^2 = 0.8580. This computes to a length weight relationship (W = aL^b) of W = 8.28x10^-3L^3.39 indicating allometric growth.
Mummichog (Fundulus heteroclitus)
Length Frequency Analysis, 2001-2002
Weight on Length Regression Analysis, 2001-2002
A small sample of 29 fish were collected during the late 2002-2003 season for length frequency and regression analysis.
Length Frequency Analysis, 2002-2003
The length frequency histogram, with normal curve superimposed, indicates essentially a single cohort with a size distribution of 3.0 - 7.8 cm. A careful examination of the graph indicates younger fish in the 3.0 - 3.8 cm size range followed by slightly older fish in the 4.0 - 6.0 cm size group, followed by a group in the 6.2 - 7.8 cm size range. All these fish were probably spawned in the same season, but sequentially. Three breeding adults in the 8.2 - 8.6 cm size range were also part of the collection.
Weight on Length Regression Analysis, 2002-2003
Computing a regression of weight on length for the sample indicated a regression equation of Y = 3.34X - 1.97510, r^2 = 0.8176. This computes to a length weight relationship (W = aL6b) of W = 1.06x10^-2L^3.34.
Striped Bass (Morone saxitilis), 2002-2003
Thirty-seven striped bass were subjected to length frequency and regression analysis.
Length Frequency Analysis
The histogram, with normal curve superimposed, clearly indicates three non-overlapping size cohorts (3-8 cm, 9-15 cm, and 17-24 cm). These animals clearly use the estuary as a nursery and feeding ground, and migrate within the estuary following the tidal oscillations.
Weight on Length Regression Analysis
Computing a regression of weight on length for the sample indicated a regression equation of Y = 2.94X - 1.80876, r^2 = 0.9818. This computes to a length weight relationship (W = aL^b) of W = 1.55x10^-2L^2.94.
Winter Flounder (Pseudopleuronectes americanus), 2002-2003
Eighteen winter flounder were subjected to length frequency and regression analysis.
Length Frequency Analysis
An examination of the length frequency histogram with normal curve superimposed indicates that the estuary serves as a feeding ground for juvenile winter flounder in the size range of 3.7 - 6.4 cm standard length. This is consistent with observations in other estuaries in the New York Tri-State Region.
Weight on Length Regression Analysis
Computing a regression of weight on length for the sample indicated a regression equation of Y = 3.09X-1.88197, r2 = 0.9903. This computes to a length weight relationship (W = aL ^b) of W = 1.31x10^-2L^3.09 indicating isometric growth.
Methods
From June 2002 until September 2003, Lehman College sampled by boat at the mouth of the river, and in tidal reaches to help identify which species are present in the river and approach the dams. Multiple freshwater stations were sampled upstream and downstream of the dams beginning in June 2002. Sampling for fish prey items was conducted at all sites.
In the estuary, fish were caught using a 12-foot wide Shrimp Trawl with #9 (1 1/2 inch) stretch mesh body and #15 (1 1/4 inch) stretch mesh cod end bag, 3/8 inch by 100-foot length tow lines (to provide a 3:1 line out to depth ratio) and 12x24 inch doors run off the stern deck of the "Privateer", towed at an average speed of 2.0 knots between the mouth and Lafayette Avenue. Tows were run both up-river and down-river, when run down-river trawls were pulled at a velocity faster than the current velocity.
Shore sampling of fish and invertebrates involved the use of a 4x4 foot push seine, with 1/4 inch stretched nylong mesh. The net was set just offshore and fish were scared into it by people stomping in from the shore or the net was pushed through the near-shore vegetation and bank overhangs. In the lower estuary, a 4x10 foot seine was used. Here, the depth was four feet and a standard semicircular path to the shore was followed.
Minnow traps were also used for near-shore sampling. These were placed randomly within the specified locations.
Station Latitude and Longitude
Bx River Estuary Mouth to Lafayette Ave., Trawl.
40°48.445'N:73°52.045'W to 40°49.053'N:73°52.814'W
Lafayette Avenue
40°49.08'N:73°52.87'W
Soundview Park
40°48.60'N:73°51.77'W
East Tremont Avenue
40°50.43'N:073°52.66'W
Drew Gardens
40°50.331-383'N:73°52.715-723'W
Sculpture Garden, 177th Street
40°50.45'N:73°52.67'W
Bx Zoo, Base of Bronxdale Waterfall
40°51.31'N:73°52.47'W
NYBG, Snuff Mill Bridge
40°51.53'N:73°52.61'W
Gear
- Trawl: 12' #9 (1 1/2 inch) Stretch mesh body, #15 (1 1/4 inch) stretch mesh cod end bag, 3/8" X 100' tow lines to 12 X 24' doors. It is a commercial Shrimp Trawl purchased from Nylon Net Co. This net is towed at a vessel speed of 2 knots behind SUNY's RV Privateer.
- Fish Traps: Standard Steel Minnow & Shrimp Traps, and Collapsible Fish Traps from Nylon Net Co.
- Push Net: 4' square Seine with 1/4 inch Stretched Nylon Mesh. Built to J. Rachlin's own design.
Downloads
Silverside data (Excel format, 284 KB)
Mummichog data (Excel format, 382 KB)
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