Alewife and Blueback Herring Captured by Intertidal Weirs of the Inner Bay of Fundy, Canada, Display Seasonal Demographics that Suggest Multiple Migrating Stocks

Abstract

Little information is available concerning the seasonal demographics of marine migrating Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis, reported in commercial fisheries as “gaspereau” in Canada and “river herring” in the USA. Once adults and age‐0 juveniles depart from coastal spawning rivers, they migrate along the North American Atlantic coast and are difficult to access for scientific analysis. During June–October 1985, a total of 3,785 Alewife and 2,343 Blueback Herring were examined for length, sex, and gonadal stage from commercial intertidal fishing weirs in Minas Basin and Cobequid Bay, Bay of Fundy, Nova Scotia. Of these, 999 adults were subsampled for total weight and body cavity fat deposits. Both species first appeared in the weirs during June, when Blueback Herring generally dominated catches. By July, catches were evenly divided between the two species, and Alewife dominated after mid‐August. Most adults were mature, and there was no discernable sex ratio pattern during the sampling period. Sampled fish exhibited abrupt changes in length, gonadal stage, condition factor, and abdominal wall and visceral mesentery fat deposits in relation to season (week), moon phase, and time of low tide. Sudden shifts in average lengths and fat deposits suggested that migrating Alewife were from different stocks. For Blueback Herring, the condition and status of fat deposits during June suggested that they were probably long‐distance adult migrators. Blueback Herring in Cobequid Bay weirs during July were probably from local stocks. Results from a total of 12,422 tagged adults that were released in Minas Basin and Cobequid Bay during 1985 supported these findings. We propose that shifts in condition and fat deposits can be used to estimate migration distance, discriminating among local, regional, and long‐distance movements.

Running on empty? Freshwater feeding by spawning anadromous alewife Alosa pseudoharengus

“…Prey consistently occurred in stomachs throughout the spawning run and K was maintained in males, with the decrease in females possibly attributed to shedding eggs. Median K of A. pseudoharengus subsampled from intertidal fishing weir catches in Cobequid Bay during June-October 1985 ranged from approximately 1.1 to 1.3 (Rulifson & Dadswell, 2020), suggesting individuals during spawning runs in our study maintained a comparatively greater K (1.3-1.5).…”

A Review of River Herring Science in Support of Species Conservation and Ecosystem Restoration

“…(2016) found stock structure at sea, with approximately 70% of the individuals caught in the U.S. midwater trawl fisheries originating from the Mid‐Atlantic stock. Rulifson and Dadswell (2020) documented temporal patterns in length, gonadal stage, condition factor, and fat deposits in migrating Alewives and Blueback Herring in Bay of Fundy weir fisheries. Taken together, these results indicate that fish from specific regions are grouped together at sea, but the at‐sea migration patterns of fish from individual rivers or from regional stocks are still unclear.…”

River- and Sex-Specific Annual Survival Rates of Mature Anadromous Alewife (Alosa pseudoharengus)

“…Life history information incorporating the interdependence of oceanic and freshwater ecosystems is critical for the management and restoration eforts of anadromous fshes [1]. Studies on commercially valuable, anadromous alosines have been motivated in recent years due to declining abundance [2][3][4]. Te larger alosines, American shad (Alosa sapidissima Wilson, 811) [5] and Hickory shad (Alosa mediocris Mitchill, 1814) [6], have been studied more often than the smaller alewife (Alosa pseudoharengus A.…”

“…Total instantaneous mortality for male and female spawning alewives was 2.06 and 1.52 which corresponded to an annual mortality of 0.87 and 0.78, respectively [19]. After spawning, adults return to sea to forage in coastal waters <100 m depth during summer and along the continental shelf during winter [4,13,20,21].…”

“…Along the eastern coast of the United States, the declining abundance of river herring triggered multiple states to impose moratoria on commercial and recreational fsheries. In Canada, however, abundance is considered stable and all commercial fsheries are active with no total allowable catch [4]. Of the 60 river populations of alewife in the Bay of Fundy, most fshing occurs in estuaries and rivers during annual spawning runs [22], with limited use of intertidal weirs in marine habitats [4,7,23].…”