INTRODUCTION

The purpose of this report is to review the existing literature on outmigrations of juvenile American Shad, Hickory shad and Blueback herring. Reviewed information will be used to best evaluate the outmigration of juvenile American shad, Hickory shad and Blueback herring from the Savannah River.

This report is being in done of support of the Savannah Harbor Expansion Project. The Savannah Harbor Navigation Channel is associated with the river estuary system. Research from other Southeast Rivers states that estuaries are used as nursery areas by juvenile anadromous fish species before migration to the ocean. The Savannah Harbor is considered an estuary and therefore must be passed through during juvenile anadromous fish outmigrations to the Atlantic Ocean. Juvenile American shad, Hickory shad and Blueback are anadromous fish species being considered in this report. Since these anadromous spcies are shown to remain in river estuary systems before joining adult ocean migrations, downriver migrations of these species and their relationship to a deepened river channel needed to be explored. Specific topics to be explored include temporal patterns of migrations of the juveniles, their location in the water column, and what they feed on. The following report explains the existing information on American shad, Hickory shad and Blueback herring in order to best explore the above mentioned specific topics.

It is noted that no research specifically on the migration of Savannah River stock of American shad, Hickory shad, and Blueback herring were found for the purposes of this report. Therefore the reviewed research in this report is generalized and should be considered not as an absolute fact but as probable patterns that would be observed in the Savannah River.

This literature review should be considered as a rapid assessment of the recommended sources of relevant information, and not an exhaustive search. Personal communication and requests for information were completed Wednesday, January 5, 2000. The absence of fisheries personnel due to the holiday season further limited the review of available information.

In order to provide all information gathered from the collected resources, all gathered resource information is presented in the List of Resources. Biographical information is listed in bold and relevant resource information listed beneath.

EXISTING DATA

A majority of existing data on migrations of juvenile American shad, Hickory shad, and Blueback herring are based on Northeastern Rivers. More extensive research has been undertaken in the Northeastern states, New England and New York in particular, to understand the causes of past declines in the anadromous species spawning runs and overall commercial catches. Northeastern Rivers in which freshwater spawning migrations are well documented include the Connecticut, Delaware and Hudson Rivers.

Research on Southeastern River spawning migrations of American shad, Hickory shad and Blueback herring exists for rivers in Georgia and South Carolina. In Georgia, the Altamaha and Ogeechee Rivers have been studied. In South Carolina, the Cooper and Santee Rivers have been studied.

A major assumption distinguishes between the above listed Northeast Rivers and the above listed Southeast Rivers concerning American shad. Spawning adult American shad are assumed to have a 100 percent mortality rate south of Cape Hatteras, North Carolina (per com Doug Cook). Southeastern American shad live to be 4 to 6 years old before joining the spawning migrations upriver to freshwater spawning habitat. The adults spawn and die soon after (Probst, 1988). American Shad in the Northeast return to spawn as many as three times before becoming spent and dying.

The assumption of 100 percent mortality for adult spawning American shad however is not absolute. Reports of tagged adult American shad being recaptured are presently being investigated in South Carolina (per com Billy McCord). Spawning marks that can be seen on scales of adult fish are physical indicator that a fish has previously spawned. In Georgia, a recent survey of anglers and other fisheries personnel found no evidence of spawning marks and thereby repeat spawning (per com Ron Michaels). Future study is needed to determine if in fact a 100 percent mortality rate should be assumed.

Northeast and Southeast migration patterns for American shad, Hickory shad and Blueback herring are shown to vary temporally. Differences between spawning migration onset, duration and completion are demonstrated when research from Northeast and Southeast Rivers is compared.

New England outmigrations are shorter in duration than Southeastern outmigrations. Migrations out to the Atlantic Ocean from the Connecticut River are complete by October (Oleary). Juvenile American shad are found in the trawling studies in Charleston Harbor from early April to early February (per com Billy McCord). Therefore migrations out the Atlantic Ocean are completed over a longer period of time. Possible reasons for the extended presence in the Harbor are favorable water temperatures year round and abundace of food. Second, New England studies largely correlate outmigrations with avoidance of cooler water temperatures. Other influences mentioned in Northeast research include flow rate and day length. In the Southeast research, peaks in outmigration may be associated with avoidance of higher water temperatures (per com Doug Cooke).

Goodwin and Adams (1969) state their observations of juvenile American shad migrations out of the Altamaha River system do not correlate with water temperatures. The data from the study supports the theory that the juvenile American shad leave the "river system" once they approach the size of 90 to 100 mm. Goodwin and Adams further state that a progressive departure of juveniles, as the juveniles approach the size of 90 to 100 cm, is probable. Goodwin and Adams point out that the size of the sample is small but are "representative" of the American shad found in the Altamaha River.

A recent study done on the Hudson River found that shad migrations may also be correlated to other factors other than avoidance of decreasing decreasing water temperatures. The study on juvenile American shad outmigrations in the Hudson River was discussed by personal communication with Kathy Hattala. Kathy Hattala explained the research done by Karen Limburg, a PhD student who did her thesis on a theory concerning the timing of juvenile American shad migration. The theory called, "Grow and Go" related to juvenile American shad migrating out of the nursery habitat when they reached a particular size. Karen Limburg could not be contacted for the purposes of this report but will eventually be contacted about her research. This study is significant because it is a deviation from existing research based on juveniles in Northeast Rivers.

Further evidence that Southeastern outmigrations are substantially different than northern outmigrations is the presence of one-year old fish outmigrating at the end of the summer months. Cooke and Chappelear discuss length data in juvenile American shad and Blueback herring. "Length data suggested that juveniles hatched in the spring begin to emigrate during their first autum. The emigration continued through the winter, past the following spring and into the summer. This resulted in some of the juveniles being over one year old before they tried to emigrate (pg. 72)." These observations support the concept that juveniles remain in the nursery area or near before outmigrating to join the migrating adult population. These individuals are premigratory juveniles.

Premigratory juveniles could be remaining in the estuaries for a period of years before joining the ocean migrating adults. Research done at Cornell University suggests that juveniles remain in the estuary and lower nursery habitat for 2 to 3 years before joining the ocean migrating adult poplulation (per com Kathy Hattala). Factors influencing the premigratory juveniles remaining in the estuary could be the availability of food.

American shad, Hickory shad and Blueback herring are different types of feeders. Juvenile American shad and Blueback herring are selective feeders that prey off small insects and larva. Hickory shad are "fish eaters." The physiology is designed to prey on other fish species larva in juvenile life stages and small fish in adult life stages (per com Billy McCord).

Feeding patterns in the nursery areas is similar for Juvenile American shad and Blueback herring. Juvenile American Shad feed on insects at the water surface and larval fish in the water column. Water surface feeding is only during night hours, juvenile American shad are negative phototrophic (Probst). During daylight hours juvenile American shad are more associated with the bottom (per com Billy McCord). As juveniles migrate to the ocean, they eventually become plankton strainers (Probst). Adults migrating upriver do not feed going upriver to the spawning areas. Blueback herring also eventually become plankton strainers. However adults migrating upriver convert back to feeding on crustaceans and larva, (Smith). No research on the nusery feeding patterns for Hickory shad was available for the purposes of this report. It should be noted that Hickory shad do not tend to use the same upriver river nursery habitat as juvenile American shad and Blueback herring. Juvenile Hickory shad tend to migrate out the estuary areas after hatching (Goodwin and Adams).

LOCATION OF JUVENILES IN THE ESTUARY WATER COLUMN

A Northeastern reference concerning the locations of American shad in the water column comes from the Connecticut River. Witherell and Kynard studied the location of adult American shad in the water colunmn of the Connecticut River. Witherell and Kynard deployed gill nets to cover the vertical profile of the Connecticut River. The majority of the adult American shad were captured in the lower half of the river depths, 83 and 73 percent at each station over the two of the study. Witherell and Kynard further define the location in the water depth by stating "most fish were caught more than 2 meters off the bottom". However, since adults are assumed to have died soon after spawning, this research can only be applied to adults entering the river in early spring. It is important to note that the Withrell and Kynard study examines adults upriver when the spawning areas, upriver from nursery areas, are reached. Research from adult spawning areas would be difficult to apply to juvenile nursery areas. Therefore the Withrell and Kynard studies can not be applied to the Savannah River juvenile American shad populations.

Witherell and Kynard simultaneously collected data on the location of adult Blueback herring in the water column during their study of adult American shad. Conclusions reached after "preliminary investigations" indicate adult Blueback herring are found at "mid-water" depths and not at "deeper water". Since Blueback herring are believed to spawn more than once in Southeast waters, data is applicable to Southeast Rivers.

Data on the location of juvenile American shad, Hickory shad or Blueback herring in a Southeastern river water column is unavailable. However, Mr. Billy McCord of SCDNR provided personal observations on the location of juvenile American shad, Hickory shad and Blueback herring in the water column. Juvenile American shad are defined as a length of 35mm (Cooke and to Cappelear, 1994) to 100mm (Ross et al., 1993). It should be noted that no one source defined the length scale of a juvenile American shad. Therefore two different sources were used to define a length scale for the purposes of this report.

Trawl studies are done monthly in the Charleston Harbor Rivers to study shrimp populations. Trawl nets are pulled from a boat near the bottom. While capture data for American shad, Hickory shad and Blueback herring are not published, Mr. McCord shared his observations of species captured in the trawl studies. From Mr. McCord's observations, the juvenile American shad are present in Charleston Harbor from November to March. The majority of the juveniles do not move out of the Charleston Harbor until late winter or early spring. Therefore the juvenile American shad leave the nursery area and move down into the estuary areas before completing the outmigrating to the ocean. Juveniles remain in estuaries longer in the Southeast because of the availability of food.

The presence of juvenile American shad in the trawl nets indicates they are bottom orientated. Mr. McCord has inspected the stomachs of juvenile American shad caught in the trawl nets. The stomachs consisted mostly of mysid shrimp. Mysid shrimp are bottom orientated organisms. Therefore juveniles outmigrating through the Charleston Harbor area are bottom orientated feeders.

American shad are more commonly caught in the Charleston Harbor trawl nets relative to the Hickory shad and Blueback herring. Mr. McCord estimates their runs are much smaller than the American Shad. The American shad are also captured for a longer period of time. Hickory shad and Blueback herring reportedly migrate out of the river before the juvenile American shad.

Probst (1988) states juvenile American shad feed on insects and crustaceans in the water column or on the surface. On the feeding patterns of American Probst states the following. "After leaving natal rivers they become plankton strainers and maintain this mode of feeding throughout the remainder of their lives." "Godwin and Adams sample a variety of habitats and found that main river channel areas adjacent to sandbars consistently produced numbers of young shad while backwaters, sloughs and other areas of reduced water flow produced few juveniles (pg 5)."

RECENT ATTEMPTS AT JUVENILE RESEARCH IN SOUTH CAROLINA AND GEORGIA

One reason for little or no data on the Southeast migration habits of clupeid and alosid species is the labor intensive nature of the data collection. Juvenile index studies were recently attempted by the South Carolina Department of Natural Resources (SCDNR). The studies were ultimately abandoned because of the lack of captures (per com Billy McCord). One possible reason for the low captures could be juveniles are so spread out throughout the estuary that it would be difficult to get data to support a conclusion.

Another example of an abandoned study comes from the Georgia Department of Natural Resources (GADNR). A ten-year study on juvenile shad in the Altamaha river was attempted in 1982. The Altamaha River study was a trawling study to correlate the number of juveniles to the number of returning adults in the Altamaha River. Even with a high number of shad returning in 1986, no correlation could be made and the study was abandoned. Unknown environmental factors were given as reasons for abandoning the study (per com Ron Michaels). Locations and temporal migration habits of juveniles were not studied in the abandoned Altamaha study.

UNIQUE SAVANNAH RIVER ANADROMOUS STOCK

Fisheries personnel contacted explained that citing research from Northern River systems or even other Southeastern rivers may not be adequate to characterize migration habits of fish species found in the Savannah River. In several instances, fisheries personnel pointed out that each fish stock from various rivers may be unique to that river.

Stocks of anadromous species could be influenced by the physical obstructions and properties of the river to make the Savannah River stock unique. Physical river obstructions could influence the migrations of anadromous fish found in the Savannah River, specifically American shad, Hickory shad, and Blueback herring. River obstructions include dams and lock structures that are physically impassible for fish without a fish passage structure or a strategy to actively transport fish upriver. An example of a strategy is the operation of the lock structure at the New Savannah Bluff Look and Dam at least 50 times during the spawning migrations of anadromous species (Walter, 1999). Physical obstructions could block spawning habitat generally described in other research. Discharges from deep reservoirs could keep the river at a cooler temperature than would normally be reached without physical obstructions. Cooler temperatures in the river, particularly in the nursery areas, may elongate the migration of the species downriver to the estuary (per com Billy McCord). All of the above mentioned properties could make anadromous species utilizing the Savannah River unique.