This may be of interest. I would think the marine sevices would know more than ANY of us
Description Source: Mass. Division of Marine Fisheries
Bluefish display an annual migration pattern that is keyed to the seasonal warming and cooling of coastal waters. They begin arriving along the southern New England coast during April and May. The earliest catches in southern Massachusetts waters occur in mid-May, but substantial numbers of fish typically do not arrive before Memorial Day. Two to 4 pound fish generally arrive first in Massachusetts waters, moving into harbors and estuaries in great numbers. Larger fish arrive somewhat later in the spring, initially inhabiting deeper waters but moving progressively shoreward into shallow areas as the summer progresses. Adult bluefish largely disappear from coastal waters of southern New England during October as water temperatures cool to 60 degrees F. Adults may occasionally stray far southward during the winter; one bluefish tagged off the coast of New York was recaptured in January three years later off the coast of Cuba. Although many adult fish migrate southward in the fall, their major migratory movement appears to be offshore toward the warmer, deep waters of the continental shelf.
Bluefish occurring between Cape Hatteras, North Carolina and New England spawn between June and August. Spawning occurs primarily offshore over the continental shelf when water temperatures warm to between 64 and 74 degrees F. After hatching, larvae inhabit surface waters and are swept along the continental shelf by prevailing currents. The number of offspring surviving to enter the population in a given year is influenced by the circulation patterns of currents on the continental shelf. If larvae move shoreward to suitable habitats, many survive; if they are moved further away from shore off the continental shelf, high mortality caused by starvation results.
In New England waters, the bluefish has a long history of periods of abundance interspersed with periods of scarcity. Records from Colonial times indicate that bluefish populations collapsed from high to low densities in New England during the mid-18th century. Similarly, the number of bluefish was greatly reduced along the north shore of Massachusetts Bay twice between the mid-19th and 20th centuries. Bluefish south of Cape Cod Bay showed a pattern of high densities prior to 1930, low densities from that time to the mid-1940s, and a rebound to high densities by 1950.
These cycles of abundance and scarcity, typical throughout the east coast, are greatly influenced by annual reproductive success and the survival of offspring.
In recent years, the total harvest by recreational anglers (which is typically at least 90% of the total fishing harvest) has been reasonably stable, although a 40% decline in angler harvest occurred from 1980 and 1984. Snapper and 1-year-old bluefish have dominated recreational catches since 1979, and fish over 8 years of age have been landed only rarely during the same time period. The number of reproductively mature fish has declined 55% since its most recent peak in 1979, dropping the estimated number of adults coastwide to a level similar to that of the mid-1970s. The current fishery is being harvested at or slightly above a level that bluefish populations can sustain.