Friday, February 11, 2011

Atlantic Sturgeon in the Delaware River

The sturgeon family is among the most primitive of the bony fishes. The shortnose sturgeon shares the same general external morphology of all sturgeon. The body surface contains five rows of bony plates or "scutes." Sturgeon are typically large, long-lived fish that inhabit a great diversity of riverine habitat. Sturgeon are found from the fast-moving freshwater riverine environment downstream and, for some species, into the offshore marine environment of the continental shelf.

Atlantic sturgeon are similar in appearance to shortnose sturgeon (Acipenser brevirostrum), but can be distinguished by their larger size, smaller mouth, different snout shape, and scutes.Atlantic sturgeon have been aged to 60 years. (There is generally faster growth and earlier age at maturation in more southern populations.)

In their estuarine and freshwater habitats, Atlantic sturgeon face additional threats, including habitat degradation and loss from various human activities such as dredging, dams, water withdrawals, and other development. Some populations are being impacted habitat impediments including locks and dams and ship strikes (e.g., Delaware and James Rivers). 

Each river system in which Atlantic and shortnose sturgeon occur is considered to contain a unique stock despite the mixing of individuals in coastal waters. A review of Atlantic sturgeon stock status in 1998 by the National Marine Fisheries Service and the U.S. Fish and Wildlife Service concluded that although the abundance of sturgeon had declined significantly, adequate spawning stock still remained for the persistence of the population and for juvenile production. Habitat improvements and fisheries conservation were recommended to improve the likelihood of full population recovery.

Video from NJN on the unique Atlantic sturgeon population found in the Delaware River

Shortnose sturgeon were federally listed in 1967 as an endangered species but in some systems abundance may be increasing to levels that would allow reconsideration of their endangered status. For example, the shortnose population in the Saint John River, New Brunswick Canada is among the largest in North America, and the Hudson and Delaware Rivers also support significant numbers of shortnose sturgeon.

Stock abundance of Atlantic and shortnose sturgeons steadily declined throughout the 20th century as a result of overfishing and habitat destruction. Fisheries for Atlantic sturgeon existed until 1997 when a moratorium was declared from Maine to Florida. 

Research into the biology, habitat requirements and stock status of both of sturgeons continues, with the goal of restoring both species to sustainable levels of abundance.

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