Understanding the Efficacy of Fish Ladder Use by Alewife ( Alosa pseudoharengus)

• Main Author: Sullivan, Kevin M.
• Language: EN
• Published: University of New Hampshire 2017
• Subjects: Zoology|Natural resource management
• Online Access: http://pqdtopen.proquest.com/#viewpdf?dispub=10620218

<p> River herring, the collective name given to North American populations of Alewife (<i>Alosa pseudoharengus</i>) and Blueback Herring (<i> A. aestivalis</i>), are iteroparous, anadromous members of the family Clupeidae, with similar morphology, ecological roles, and overlapping distributions. Once abundant in coastal rivers of New Hampshire, many factors including commercial fishing, habitat degradation, and dam construction resulted in a precipitous decline of the species along the entire coast. Successful efforts to restore populations have included the construction of fish ladders at dams. However, fish ladders require constant operation and maintenance to efficiently pass river herring, and only provide access to spawning habitat up to the next barrier, all too often, man-made.</p><p> Alewife passage efficiency in fish ladders of all designs has received little attention historically, but is important to understand how to interpret annual counts, that for many rivers are the only index used in current stock assessments. In this study, passive integrated transponder (PIT) tags were used to assess the passage efficiency of a Denil fish ladder on the Lamprey River in Newmarket, New Hampshire. The data collected allow for a better understanding of the movements and diel behavior of river herring in fishways, as well as insight into how the selectivity of fish ladders my shape the population demographics within a river system.</p><p> A breached dam located at Wadleigh Falls on the Lamprey River in Lee, New Hampshire was examined to determine if river herring were able to pass the existing structure or if it should be considered the upper extent of their annual spawning migration. Telemetry data indicated that Alewives were unable to pass the breached Wadleigh Falls Dam site and that it should be considered the uppermost extent of their migratory access. Results also show that migrating fish arriving at the location had a strong preference for the river-right channel when migrating upriver and exhibited very little exploratory behavior to seek alternate pathways upriver before emigrating back downriver, approximately two weeks after river entry. These in-river residence times were very similar to those found in other telemetry studies of anadromous Alewives. </p><p> Successful management and effective stock assessment for any species requires an understanding of its reproduction and recruitment. Fecundity is one measure of the reproductive potential of a species and was assessed in this study. Mature adult Alewives were collected at the head-of-tide dam on the Lamprey River in Newmarket, New Hampshire during the vernal spawning migration in 2012. A gonadosomatic index was used to determine that fish were sampled before spawning occurred, and egg diameters were quantified to examine distribution of eggs throughout the ovary. Fecundity was estimated gravimetrically using two techniques for comparison, and no difference between the methods was found. These findings show that image analysis is a fast and reliable method for fecundity estimation that does not require the use of a commonly used, toxic solution for ovary preservation. Fecundity estimates using image analysis ranged from 147,400 eggs at 24 cm to 332,500 eggs at 34 cm and aligns with previous findings of a clinal trend along the Atlantic Coast. Fecundity increased with total length, somatic weight, and age. Simple linear regressions exhibited good fits for fecundity-total length and fecundity-somatic weight, with age being the best predictor.</p><p>