Overview
The medium pelagics group is made up of striped bass and bluefish, both of which support important recreational fisheries and, to a lesser degree, commercial fisheries. Striped bass are an anadromous species, which means they migrate into freshwater to spawn. This occurs primarily in the Mid-Atlantic Bight, after which adults migrate to northern feeding grounds in the spring and summer. Bluefish spawning begins off of Cape Hatteras as early as May, and moves northward to Cape Cod as waters warm. Peak spawning for the species occurs in July and diminishes in the late summer (Smith et al. 1994). After a planktonic stage offshore, bluefish juveniles recruit to estuaries and nearshore environments and are attractive targets for the recreational fishery. Bluefish, like striped bass, migrate northward as water temperatures warm.
- Gulf of Maine
Both bluefish and striped bass are rare in Gulf of Maine during the spring, as the two species move northward from the Mid-Atlantic during the late spring and summer as waters warm. As such, records of the two species in spring survey data in Gulf of Maine are sparse, although evidence for their presence in Gulf of Maine can be seen in the NEFSC fall bottom trawl survey. From the 1970s to early 1990s, bluefish were the dominant species of the two in terms of fall survey abundance. From the 1990s to early 2000s, striped bass became more prevalent in the Gulf, and then bluefish again were the largest contributors to biomass from 2006 to 2015.
- Georges Bank
Similar to Gulf of Maine, bluefish and striped bass are rare in the offshore regions of Georges Bank during the spring survey. In fall survey data, bluefish were the most prevalent species from the early 1970s until the mid-1990s, when striped bass became more common in the survey. This trend lasted for around 10 years, and from about 2007 onwards, bluefish have again become dominant in terms of fall survey biomass.
- Mid-Atlantic Bight
In the warmer waters of the Mid-Atlantic Bight, bluefish and striped bass are present in spring survey data. Striped bass are typically the most dominant contributor to medium pelagic biomass in the Mid-Atlantic during the spring survey, and appear to be increasing relative to bluefish biomass during the fall. This is because fall surveys suggest no change in bluefish abundance while striped bass are increasing, as the proportion of bluefish biomass in this group has significantly decreased since the mid-1970s.In the winter, larger bluefish remain in the Mid-Atlantic while smaller individuals move further south.
Ecological Interactions
Bluefish and striped bass are primarily predators, although their eggs, larvae and juveniles are prey to other species. Adult bluefish have a diet composed mostly of other fish and squid (Buckel et al. 1999, Fahay et al. 1999). Striped bass are omnivorous, feeding on a variety of invertebrates and inshore fish species, especially menhaden and river herring (Walter et al. 2003). While bluefish and striped bass have the potential for competition for resources, particularly between juveniles which use the same estuaries, studies have shown that there is no evidence for such competitive effects (Buckel and McKown 2002).
Environmental Drivers
Water temperature is an important driver for both bluefish and striped bass. The distribution of bluefish is related primarily to water temperature as they do not often occur in temperatures less than 14-16°C (Bigelow and Schroeder, 1953). Because of this, they are warm water migrants traveling north starting in the spring and returning south and further offshore in the fall (Fahay et al. 1999). Striped bass which spawn in Chesapeake Bay, Delaware River and the Hudson River migrate from North Carolina to Nova Scotia during the summer months, move north into feeding grounds during spring and summer (Nelson et al. 2003).
Human Activities
The primary human activity which affects bluefish and striped bass is fishing. Historically, striped bass were one of the most important commercial fisheries along the coast, with so many caught that they were used as fertilizer (Nelson 2018). The fishery collapsed in the 1980’s and has since been rebuilt. Most of the fish caught by recreational anglers are released (73-90% since 2003). Bluefish historically was more of a recreational fishery but since the early 90’s the proportion of commercial fisheries has increased. Both species are managed by the Atlantic States Marine Fisheries Commission (ASMFC) and in the case of bluefish - jointly with the Mid-Atlantic Fishery Management Council (MAFMC).
