Alex Haro

A passive integrated transponder (PIT) tag system for monitoring fishways

Abstract An application of passive integrated transponder (PIT) technology was used to monitor movements of adult American shad ( Alosa sapidissima ), blueback herring ( A. aestivalis ) and gizzard shad ( Dorosoma cepedianum ) in two experimental fishways. Tag reading efficiency was between 88–96%, detection ranges were 50–100 cm from orifices of 3100–9600 cm 2 , and read rates were 5–7 Hz. The system was limited by the amount of time that tags were exposed to the energize/detect zone, and by simultaneous presences of large numbers of tags within this zone.

Population Decline of the American Eel: Implications for Research and Management

Abstract We present evidence for a decline in the population of the American eel (Anguilla rostrata) from several widely distributed regions of North America from 1984 to 1995. Trends in population indices from commercial catch data, upstream passage counts, and seine, trawl, and electrofishing surveys were analyzed and found to be either not significant or significantly negative. Explanations for this decline, whether natural or anthropogenic, are unknown, due to variation and incompleteness in abundance data, and incomplete knowledge of eel life history, ecology, and population dynamics. A number of potential factors may be contributing to the decline, including (in alphabetical order): barriers to migration, habitat loss and alteration, hydro turbine mortality, oceanic conditions, over-fishing, parasitism, and pollution. The paucity of life table data associated with the unconventional life history characteristics of anguillid eels (catadromy, panmixis, semelparity, high age at maturity, wide geographi...

Effect of Water Acceleration on Downstream Migratory Behavior and Passage of Atlantic Salmon Smolts and Juvenile American Shad at Surface Bypasses

Abstract Behavior and passage rate of smolts of Atlantic salmon Salmo salar and juvenile American shad Alosa sapidissima were compared between a standard (sharp-crested) and a modified surface bypass weir that employs uniform flow velocity increase (1 m·s−1·m−1 of linear distance). Within the first 30 min after release, significantly more smolts passed the modified weir than the standard weir, but no differences in passage rate between weir types were noted for juvenile American shad. More Atlantic salmon smolts and juvenile American shad were passed by the modified weir in groups of two or more than were passed by the standard weir. Mean lengths of passed and nonpassed smolts were not significantly different between weir types, but American shad passed by the sharp-crested weir were significantly smaller than nonpassed fish. Most individuals of both species that passed the modified weir maintained positive rheotaxis and strong swimming throughout the length of the weir. In addition to acceleration, visua...

Factors regulating the downstream migration of mature eels (Anguilla spp.) at Aniwhenua Dam, Bay of Plenty, New Zealand

Abstract The downstream migrations of mature longfinned eels (Anguilla dieffenbachii Gray, 1842) and shortfinned eels (Anguilla australis Richardson, 1848) were investigated at Aniwhenua Dam on the Rangitaiki River between 1992 and 1998. Migrants were mostly females over 1000 mm total length (TL) with otoliths indicating rapid growth rates. Migrations, which occurred on a few nights each autumn, generally began once water temperatures began to decline and ended when temperatures dropped below c. 11 °C. Rainfall and flow increases were found to be key factors triggering migration events. Rainfall exceeding a cumulative total of 40 mm over 3 days accounted for 60% of migrant eels arriving at Aniwhenua. It is proposed that such rainfall triggers could be used as predictors to instigate mitigation activities that would allow mature eels to proceed uninjured past barriers such as hydro‐electric dams.

Downstream Migration of Silver-Phase Anguillid Eels

Downstream migration of adult anguillid eels in freshwater habitats marks the end of a long, generally slow growth phase, abandonment of a home range, and initiation of a seaward spawning migration. Although different species of Anguilla exhibit variation in characteristics of this migratory phase, some generalized traits in migration are common to most species. For temperate and subtropical species of Anguilla,migratory periods are usually associated with times of year when water temperatures are decreasing and flows are increasing. Species of Anguilla in the northern hemisphere usually emigrate between the months of August and December, while those of the southern hemisphere leave freshwater habitats between January and March. In the northern hemisphere, A. rostrata tends to emigrate earlier at higher latitudes (Fig. 1). However, Tesch (1977) concluded that the migration date of A. anguilla could not be predicted on the basis of geography alone. Onset of the silver migratory phase is generally morphologically characterized in most species of Anguilla as a darkening of dorsal surfaces and fin margins, silvering of lateral integument, enlargement of eye diameter, and an increase in gonad development (Lecomte-Finiger 1990). Other endocrinological changes also occur during metamorphosis (Durif et al. 2000).

Effect of Slope and Headpond on Passage of American Shad and Blueback Herring through Simple Denil and Deepened Alaska Steeppass Fishways

Abstract Passage and transit time of adult upstream-migrant American shad Alosa sapidissima and blueback herring A. aestivalis were investigated in standard Denil and Alaska steeppass fishways with variable slope and headpond under semicontrolled conditions. Percent of American shad passed per unit time (percent passage) increased with temperature, while time required to ascend from the fishway entrance to the exit (transit time) decreased with increasing temperature for both species. Increasing fishway slope decreased percent passage of American shad, regardless of fishway type. Higher fishway slope decreased percent passage of blueback herring in the steeppass fishway only. Low headpond enhanced percent passage of American shad in the Denil fishway, but decreased percent passage of American shad in the steeppass fishway. Headpond level had no effect on percent passage of blueback herring in either fishway. Because headpond level in the steeppass fishway affected percent passage of American shad but not ...

Evaluation of Nature-Like and Technical Fishways for the Passage of Alewives at Two Coastal Streams in New England

Abstract Nature-like fishways have been designed with the intent to reconnect river corridors and provide passage for all species occurring in a system. The approach is gaining popularity both in Europe and North America, but performance of these designs has not been quantitatively evaluated in a field setting for any North American species. Two nature-like fishways and three technical fishways in New England were evaluated for passage of anadromous adult alewives Alosa pseudoharengus by using passive integrated transponder (PIT) telemetry. A perturbation boulder rock ramp (32 m long; 4.2% slope) constructed in Town Brook (Plymouth, Massachusetts) passed 94% of the fish that made passage attempts, with most fish ascending the ramp in less than 22 min. In the East River (Guilford, Connecticut), a step-pool bypass design (48 m long; 7.1% slope) passed only 40% of attempting fish, with a median transit time of 75 min. In Town Brook, a technical pool-and-weir fishway (14 m long; 14.3% slope) exhibited poor en...

Passage of American Shad: Paradigms and Realities

Abstract Despite more than 250 years of development, the passage of American shad Alosa sapidissima at dams and other barriers frequently remains problematic. Few improvements in design based on knowledge of the swimming, schooling, and migratory behaviors of American shad have been incorporated into passage structures. Large-scale technical fishways designed for the passage of adult salmonids on the Columbia River have been presumed to have good performance for American shad but have never been rigorously evaluated for this species. Similar but smaller fishway designs on the East Coast frequently have poor performance. Provision of effective downstream passage for both juvenile and postspawning adult American shad has been given little consideration in most passage projects. Ways to attract and guide American shad to both fishway entrances and downstream bypasses remain marginally understood. The historical development of passage structures for American shad has resulted in assumptions and paradigms about American shad behavior and passage that are frequently unsubstantiated by supporting data or appropriate experimentation. We propose that many of these assumptions and paradigms are either unfounded or invalid and that significant improvements to American shad upstream and downstream passage can be made via a sequential program of behavioral experimentation, application of experimental results to the physical and hydraulic design of new structures, and controlled tests of large-scale prototype structures in the laboratory and field.

Survival and Behavioral Effects of Exposure to a Hydrokinetic Turbine on Juvenile Atlantic Salmon and Adult American Shad

This paper describes a series of experiments designed to measure the effect of exposure to a full-scale, vertical axis hydrokinetic turbine on downstream migrating juvenile Atlantic salmon (N = 175) and upstream migrating adult American shad (N = 208). Controlled studies were performed in a large-scale, open-channel flume, and all individuals approached the turbine under volitional control. No injuries were observed, and there was no measurable increase in mortality associated with turbine passage. Exposure to the turbine elicited behavioral responses from both species, however, with salmon passing primarily over the downrunning blades. Shad movement was impeded by the device, as indicated by fewer attempts of shorter duration and reduced distance of ascent up the flume. More work should be performed in both laboratory and field conditions to determine to what extent these effects are likely to influence free-swimming fish.

Environmental Effects of Hydrokinetic Turbines on Fish: Desktop and Laboratory Flume Studies

A primary issue of concern of regulatory and resource agencies is how the operation of hydrokinetic turbines will affect local and migratory fish populations. This collection of three reports describes desktop and laboratory flume studies that provide information to support assessment of the potential for injury and mortality of fish that encounter hydrokinetic turbines of various designs installed in tidal and river environments.