性吧导航

In a surprising discovery, researchers from the Academy of Natural Sciences of 性吧导航 found a substantial number of anadromous Blueback Herring in New Jersey鈥檚 Cooper River. The fish, which like salmon, swim up-river to spawn, had been considered all but extinct in the region by the 1970s. But the finding suggests they have made a robust return in the river, which is somewhat unexpected considering the area along it remains highly urbanized. The finding suggests that the herring鈥檚 return corresponds with improvements in water quality and fish passage over the last 50 years.

Recently published in the journal the research reports that highly urbanized rivers can and, in some cases, do support substantial runs of anadromous fishes.

Rivers on the east coast of North America, like the Cooper, used to teem with fish migrating upstream from salt water to freshwater to reproduce 鈥� but historically viable stocks have weakened as waterways were dammed and water quality deteriorated well through the adoption of in 1972.

鈥淚n the 鈥�50s, 鈥�60s and 鈥�70s, water quality was very poor and when the Clean Water Act was passed, it took time for the legislation to influence infrastructure and divert discharge from water treatment plants that were discharging directly to the Cooper River,鈥� said David Keller, PhD, head of the Fisheries Department at the Academy of Natural Sciences of Drexel and lead author on the study. 鈥淏y the 鈥�90s these fish were able to be observed again, and a fish ladder was installed 鈥� now as water quality improves and migratory fish can reach historical spawning grounds, we are seeing the return of several species, like American Shad, but most remarkably a robust return of Blueback Herring.

The study took place within the Cooper River watershed and Delaware River basin located in the mid-Atlantic region of North America 鈥� in tidal portions above and below the Kaighn Avenue Dam. The research team surveyed the area in the spring and summer of 2022 and 2023, overall collecting six anadromous species including Blueback Herring, Hickory Shad, Alewife, American Shad, Striped Bass, and Sea Lamprey. 

鈥淎s a general pattern, our results indicated that densities of these fishes, mostly Blueback Herring and Striped Bass, were lower above the dam in both years, suggesting that the dam may be impeding runs of those species, or that the fish ladder may be inadequate,鈥� said Keller.

Collection results suggest that Cooper River Lake may provide suitable spawning habitat for these species or access to spawning grounds upstream 鈥� leading the team to emphasize the importance of considering urbanized watersheds on the east coast of North America as candidates for restoration 鈥� despite having high urban land uses typically associated with poor habitat quality.

Researchers aim to better understand anadromous fish relationships with urbanization as it relates to critical factors, such as low dissolved oxygen and high temperatures that negatively affect habitat suitability for the many life stages of these fishes.

鈥淐ontinued efforts to address the urban syndrome through management practices has improved water quality, as evidenced by the return of Blueback Herring, a species that requires good dissolved oxygen levels in the Cooper River and Cooper River Lake,鈥� said Keller.

Researchers concluded that continued monitoring of urbanized streams is needed to better describe the long-term response of these species to efforts that ameliorate ecological disturbances caused by urbanization.

The team conducted weekly sampling of the Cooper River in 2024 and additional collection is planned for spring 2025 to further understand the spatial and seasonal patterns of anadromous fish recovery near the dam.

This research was supported by Upstream Alliance鈥檚 鈥淒eveloping a Water Trail and Recreational Programming for Camden, NJ鈥� project, the U.S. Fish and Wildlife Service, the National Fish and Wildlife Foundation鈥檚 Delaware Watershed Conservation Fund (Grant ID: 0403.21.072066), and the Academy of Natural Sciences. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the U.S. Government or the National Fish and Wildlife Foundation and its funding sources.

In addition to Keller, Colin Rohrback and Daniel Morrill participated in this research while at the Academy.

Read the full paper here: