A New Paradigm in Alewife Migration: Oscillations between Spawning Grounds and Estuarine Habitats

Abstract

The current paradigm in Alewife Alosa pseudoharengus migrations is shifting from a single reproductive event and rapid movement in and out of freshwater to one that recognizes more nuanced movements and asynchronous batch spawning. In this study, Alewives (n = 72) were acoustically tagged in the Carmans River, Long Island, New York, a small coastal river with restored fish passage. Our objective was to examine fine-scale spatial movements in the tidal and reconnected habitats to identify spawning behavior patterns, including habitat use and spawning periodicity, that can be applied to fishway restoration and species management. Alewives that completed their spawning migration (n = 27) exhibited variability in posttagging trajectories, residency, passage rate, and behavior. The current paradigm consisting of a single upstream migration followed by a downstream migration was only seen in 26% (n = 7) of fish, while 41% (n = 11) deviated from the paradigm and made multiple reversals and numerous movements on and off the spawning grounds. Oscillations spanned from the estuary into the reconnected habitat and resulted in a proportionally large amount of time spent in the estuarine and brackish habitats. Some oscillations also consisted of multiple fishway passage events within a season. Oscillation behavior is likely a naturally occurring spawning strategy that has gone undetected. Consequently, the proportion of individuals of a population that display single versus multiple passage events could result in fishway counts that bias run size estimations and thus population assessments.

Feasibility of using surgical implantation methods for acoustically tagging alewife (Alosa pseudoharengus) with V5 acoustic transmitters

“…The tagging protocol was adapted from methods described in previous studies on alewife [ 18 , 19 ], Pacific herring [ 16 , 17 ], and Atlantic salmon ( Salmo salar ) smolts [ 35 ], and the location of the incision site was based on passive acoustic transponders (PIT) tagging practices [ 36 ]. Fish were anesthetized with a buffered solution of 200 mg/L MS-222, and morphometric measurements (sex, weight and fork length) were recorded ( Table 1 ).…”

“…This study used V5 acoustic tags. These transmitters are substantially smaller than models used in previous studies on clupeids [16][17][18][19] and reduce the tag burden on animals, as well as potentially eliminate the need for suturing. Our pilot trials tested the feasibility of not suturing incisions in alewife.…”

“…Few tagging studies have been performed on clupeids, with most of these focusing on the Pacific herring ( Clupea pallasii ) [ 16 , 17 ]. Even fewer data exist for alewife [ 18 , 19 ]. This is in part because clupeids are susceptible to scale loss, infection, and behavioural changes when handled [ 9 , 10 , 20 ].…”

Surgical Implantation of Acoustic Tags in American Shad to Resolve Riverine and Marine Restoration Challenges

“…In contrast, studies of alosines have been predominately focused on the time spent in rivers by spawning adults (e.g., Barry and Kynard 1986;Hightower and Sparks 2003;Bailey et al 2004;Sprankle 2005;Harris and Hightower 2011;Grote et al 2014;Raabe et al 2019). Alosines are considered relatively "fragile" fish (Hendricks 2003); as a result, historic and recent telemetry studies of these species have used gastric tagging (e.g., Dodson et al 1972;Acolas et al 2004;Frank et al 2009;Grote et al 2014;Eakin 2017;McCartin et al 2019) or external tagging (Breine et al 2017) methods, although Bolland et al (2019) tagged a small number of Twaite Shad Alosa fallax surgically. While all tagging methods incur some risk to the health of the fish, surgical methods are often considered more stressful than other methods (Nielson 1992;Winter 1996; Castro-Santos and Vono 2013), but no formal examinations exist for many species.…”

“…; Eakin ; McCartin et al. ) or external tagging (Breine et al. ) methods, although Bolland et al () tagged a small number of Twaite Shad Alosa fallax surgically.…”