Boyd Kynard

Sturgeon rivers: an introduction to acipenseriform biogeography and life history

We present an overview of the global distribution of all 27 living species of Acipenseriformes in an attempt to understand their biogeographic history and the range of life history patterns displayed by different species. Our biogeographic analysis (based on the most recent phylogenetic analysis including fossil Acipenseriformes) suggests that Acipenseriformes originated in Europe, and that early diversification took place in Asia. Acipenseriformes do not have a common life history; variation within and between species is the rule rather than exception. The few relatively well-known case studies (e.g., Caspian Sea sturgeons, European Atlantic sturgeons in the Gironde system, and shortnose and North American Atlantic sturgeons in rivers of the east coast of America) greatly influence what we think we know about sturgeon biology. Our present level of phylogenetic understanding does not allow us to determine whether anadromy or potamodromy is the plesiomorphic life history pattern for Acipenseriformes. We propose that rivers in which spawning occurs must be the central unit for biogeographic analysis of living Acipenseriformes. After mapping these rivers, we recognized nine biogeographic provinces for acipenseriforms. Some repeated historical patterns emerge from this analysis, but, again, we are limited by our current understanding of phylogenetic relationships within the genus Acipenser in particular. Distribution and biogeographic data are central to deciding where to make new efforts to update existing status information for acipenseriform species. We single out a widely ranging and highly variable species, Acipenser ruthenus, as particularly intriguing, for it spans three of our nine biogeographic provinces, and apparently has different life history patterns in different river systems. Finally, we note new areas in need of basic research, particularly the need for more detailed descriptions and analyses of life histories of different populations of sturgeons.

Life history, latitudinal patterns, and status of the shortnose sturgeon Acipenser brevirostrum

Historically, shortnose sturgeon inhabited most major rivers on the Atlantic coast of North America south of the Saint John River, Canada. Today, only 16 populations may remain. Major anthropogenic impacts on shortnose sturgeon are blockage of spawning runs by dams, harvest of adults (bycatch and poaching), dredging of fresh/saltwater riverine reaches, regulation of river flows, and pollution. The pattern of anadromy (adult use of salt water) varies with latitude. The pattern may reflect bioenergetic adaptations to latitudinal differences between fresh and salt water habitats for thermal and foraging suitability. The greater adult abundance in northern and north-central populations likely reflects a historical difference with southern populations that is currently accentuated by increased anthropogenic impacts on southern populations. Adult abundance is less than the minimum estimated viable population abundance of 1000 adults for 5 of 11 surveyed populations, and all natural southern populations. Across the latitudinal range, spawning adults typically travel to about river km 200 or farther upstream. Dams built downstream of spawning reaches block spawning runs, and can divide amphidromous populations into up- and downstream segments. Conservation efforts should correct environmental and harvest impacts, not stock cultured fish into wild populations.

Field and laboratory observations of spawning periodicity and behavior of a northern population of the Atlantic silverside, Menidia menidia (Pisces: Atherinidae)

SynopsisThe spawning periodicity and mating behavior of a northern population of the Atlantic silverside, Menidia menidia, was studied both in the field (Salem Harbor, Massachusetts) and in laboratory experiments. Spawning in the field coincided with new and full moons. Under conditions of unlimited food availability in artificial outdoor pools that received natural celestial illumination or in indoor aquaria receiving no evening illumination, spawning occurred every 1–3 days rather than fortnightly. These results suggest that tidal influences are a primary factor that synchronizes spawning in M. menidia. Published reports of diel time of spawning in both marine and freshwater species of Menidia indicate a generic tendency to spawn during mid-morning. This pattern coupled with high tides that cover suitable spawning substrates during mid-morning only at fortnightly intervals could account for the semilunar spawning cycle in marine populations of Menidia. Although general characteristics of the reproductive ecology of M. menidia in Massachusetts were similar to a thoroughly studied population in South Carolina, several differences were evident. The breeding season was shorter in Massachusetts (late; April–June), and occurred over a much lower range of temperatures (9–21°C). Intensity and frequency of spawning was correlated with the height of high tide. Eggs were deposited only on mats of intertidal, filamentous algae rather than on roots or stems of Spartina alterniflora or other intertidal vegetation. Promiscuous spawning occurred in small, highly male-dominated groups of fish, primarily after the tide had begun to recede, and often at the waters edge. No predation on spawning adults was observed but the mummichog, Fundulus heteroclitus, fed daily on developing embryos during high tide.

Attraction of Adult American Shad to Fish Lifts at Holyoke Dam, Connecticut River

Abstract The movements of 18 radio-tagged American shad (Alosa sapidissima) were studied in 1980 and 1981 as they attempted to locate the upstream fish collection facilities of two fish lifts at Holyoke Dam on the Connecticut River in Massachusetts. Nine fish (50%) were passed by the lifts during the 2 years and, in 1980, the efficiency of the tailrace lift was estimated at 42%. The mean delay time of the seven fish passed by the tailrace lift during the 2 years was 3.3 d (range 2-5 d); the delay of the two fish passed by the spillway lift in 1981 was 6 and 7 d. Fish were repelled by the turbulence caused by the turbine discharge into the head of the tailrace and only entered the vicinity of the tailrace lift during 55% of all upstream trips in 1980 and 67% of the trips in 1981. During high river flows, fish were attracted to the spillage over the dam, not the flow from the tailrace. The inefficiency of either lift to pass early migrating American shad and of the tailrace lift to pass fish efficiently at ...

Yearly Movements of Shortnose Sturgeons in the Connecticut River

Abstract Movements of shortnose sturgeon Acipenser brevirostrum, an endangered species, were studied for 5 years by radio telemetry and mark-recapture in the lower 140 km of the Connecticut River to Long Island Sound. Ninety fish (range, 54–97 cm fork length; 1.2–9.2 kg weight) were equipped with radio transmitters. The cycle of annual movement consisted of several up- and downriver migrations between four discrete areas that were used for summer feeding, spawning, and over-wintering. Thus, the major portion of the river served as a conduit for movement between the areas of major use. Each year, some adults remained in fresh water. Yearly movements were complex; fish of different age classes and reproductive conditions associated seasonally in the same habitat. Received February 13, 1984 Accepted May 6, 1985

Behavior, length, and sex ratio of seaward-migrating juvenile American shad and blueback herring in the Connecticut river

Abstract The fall downstream migrations of juvenile American shad Alosa sapidissima and blueback herring Alosa aestivalis were monitored for 3 years in the Connecticut River at Holyoke Dam, Massachusetts. Decreasing water temperature—not increasing river flow—determined the time migration began and ended for both species. The migration of blueback herring began in September as water temperature declined to 21°C, peaked at 15–14°C, and ended in late October or early November at 10°C. The American shad migration began at 19°C, peaked at 14–9°C, and ended at 10–8°C. Most movement peaks were centered on quarter-moon periods; seven were centered on a new moon and none was centered on a full moon. The diel pattern of migration varied among the 3 years. In general, however, blueback herring were active throughout the 24-h period (peak activity at 1800 hours), and American shad moved in the afternoon and evening (peak activity between 1800 and 2200 hours). The migration of juvenile American shad may be mediated b...

Spawning of the Shortnose Sturgeon in the Merrimack River, Massachusetts

Abstract We tracked 10 ultrasonically tagged shortnose sturgeons Acipenser brevirostrurn during spring in the Merrimack River to investigate spawning. Seven fish in 1989 and six fish in 1990 were tracked intensively to identify the timing and location of spawning and to characterize spawning habitat. In mid-April 1989 and 1990, fish moved upstream to just below head of tide, concentrating in a 2-km reach at river kilometers 30–32 (measured from the mouth) at Haverhill, Massachusetts. The estimated spawning time was a 5-d period (26–30 April) in 1989 and an 8-d period (22–29 April) in 1990. Spawning sites covered about 10.5 ha in 1989 and 13.5 ha in 1990. Fish spawned as river temperature increased from 9.6 to 14.0°C and river discharge decreased from 390 to 240 m3/s. Physical characteristics of spawning sites were boulder–rubble substrate, water depth of 1.8–5.5 m, and bottom water velocity of 0.3–0.7 m/s. We captured no ovulating females but verified successful spawning in 1990 by capturing two live embr...

Spawning and Rearing of Shortnose Sturgeon from the Connecticut River

Abstract The shortnose sturgeon (Acipenser brevirostrum), an endangered species, was spawned in the field for the first time. One mature female yielded 62 eggs that were fertilized, of which 12 were hatched and 5 were reared to the fry stage. The eggs hatched in 8 days at 17°C. Diameter of the fertilized eggs was 3.5 mm and mean total length of the newly hatched larvae was 9.5 mm. After 2 days of active swimming, the yolk-sac fry sought concealment and were strongly photonegative. By the 12th day after hatching total length was 15 mm, the yolk sac was completely absorbed, and the fry were feeding on Zooplankton.

Comparative ontogenetic behavior and migration of kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii, from the Amur River

We conducted laboratory experiments with kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii, to develop a conceptual model of early behavior. We daily observed embryos (first life phase after hatching) and larvae (period initiating exogenous feeding) to day-30 (late larvae) for preference of bright habitat and cover, swimming distance above the bottom, up- and downstream movement, and diel activity. Day-0 embryos of both species strongly preferred bright, open habitat and initiated a strong, downstream migration that lasted 4 days (3 day peak) for kaluga and 3 days (2 day peak) for Amur sturgeon. Kaluga migrants swam far above the bottom (150 cm) on only 1 day and moved day and night; Amur sturgeon migrants swam far above the bottom (median 130 cm) during 3 days and were more nocturnal than kaluga. Post-migrant embryos of both species moved day and night, but Amur sturgeon used dark, cover habitat and swam closer to the bottom than kaluga. The larva period of both species began on day 7 (cumulative temperature degree-days, 192.0 for kaluga and 171.5 for Amur sturgeon). Larvae of both species preferred open habitat. Kaluga larvae strongly preferred bright habitat, initially swam far above the bottom (median 50–105 cm), and migrated downstream at night during days 10–16 (7-day migration). Amur sturgeon larvae strongly avoided illumination, had a mixed response to white substrate, swam 20–30 cm above the bottom during most days, and during days 12–34 (most of the larva period) moved downstream mostly at night (23-day migration). The embryo–larva migration style of the two species likely shows convergence of non-related species for a common style in response to environmental selection in the Amur River. The embryo–larva migration style of Amur sturgeon is unique among Acipenser yet studied.

Use of Radio Telemetry to Determine the Mortality of Atlantic Salmon Smolts Passed through a 17-MW Kaplan Turbine at a Low-Head Hydroelectric Dam

Abstract Mortality among 108 radio-tagged 2-year-old smolts of Atlantic salmon Salmo salar passed through a 17-MW Kaplan turbine was estimated at Holyoke Dam on the Connecticut River. The survival of test and control fish in 1981 was determined by comparing their rate of downstream movement with that of 28 prekilled fish. The survival of test fish in 1982 was determined as in 1981 by using nine prekilled fish. At full power generation, the mean percent turbine-induced mortality at 2 h (95% confidence interval in parentheses) was 11.8 (3.8–18.0) in 1981 and 13.7 (1.9–22.5) in 1982.