Modeling Predator–Prey Linkages of Diadromous Fishes in an Estuarine Food Web

Abstract

Historically, multiple species of diadromous fishes served as a coastal food source for commercially valuable nearshore predators. However, severe declines in diadromous fish populations in the nearshore Gulf of Maine (GOM) have impacted trophic dynamics and increased pressure on other estuarine‐dependent forage resources. The objective of this study was to compare the trophic positions and interspecific interactions of diadromous fishes as predators and prey in relation to current GOM forage fishes. Empirical biomass data along with diet compositions and vital rates were used to construct a static model of a representative GOM coastal food web: the Saco River estuary (SRE) in Maine. A series of sensitivity analyses based on model outputs was performed to determine the trophic role of diadromous fishes in this estuarine food web. Model results suggested that juvenile marine transients played a greater role as forage species for SRE predators than did the anadromous Blueback Herring Alosa aestivalis and Alewife Alosa pseudoharengus. Due to the abundant forage fish base, Atlantic Sturgeon Acipenser oxyrinchus and Shortnose Sturgeon Acipenser brevirostrum were estimated to have a greater trophic position than reported in past literature. Lower‐trophic‐level fishes functioned as keystone prey species for sturgeon. The use of holistic approaches to update the ecological data on predator–prey interactions among diadromous fishes and forage resources within coastal ecosystems is necessary for the future management of these ecologically significant and threatened species. Received January 4, 2016; accepted May 20, 2016

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

“…Similar top‐down effects (Figure 8, interaction A) have been found in a mass‐balanced food web model of a Gulf of Maine estuary in which Striped Bass and piscivorous ducks had a modest negative effect on river herring (Smith et al. 2016). Recent declines in Striped Bass abundance could provide a natural experiment revealing the impact of coastwide Striped Bass abundance on river herring abundance (NEFSC 2019); the prediction would be an increase in river herring in response to a decrease in Striped Bass.…”

“…2012; Smith et al. 2016). Conversely, river herring abundance may influence the success of predator year‐classes or may have had such influence historically (Ames and Lichter 2013; McDermott et al.…”

Opening the tap: Increased riverine connectivity strengthens marine food web pathways

“…In addition to the impacts on the marine environment, the loss of connectivity also affects riverine [23] and estuarine systems. There is evidence that juvenile planktivorous, such as Atlantic herring and sand lance are more dominant food base than river herring in the estuary of Saco River [63], a heavily dammed watershed, adjacent to the watersheds of our study. Atlantic herring stock projections show a high likelihood of overfished and overfishing status in the future, due to sustained low recruitment since 2011 [64].…”

Distribution, abundance, and species composition of fish larvae and juveniles of Gobiidae in the Cimaja estuary, Palabuhanratu, Indonesia

“…The high level of diversity and richness of fish species found in the estuary area is clear evidence of the increased productivity and role of the estuary area for various fish species [5]. Many fish species from catadromous, anadromous, and amphidromous can be found in the estuary area [6]. Estuaries are also a transitional area for diadromous fish at certain stages in their lives [7].…”