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Abridged report for PFBC website
Michael L. Hendricks
and
Earl M. Myers

Pennsylvania Fish and Boat Commission
Division of Fish Production Services
State College, PA


INTRODUCTION

This report summarizes the results of bio-monitoring activities for juvenile alosines conducted in the Susquehanna River and its tributaries in 2005.

The Conowingo West Fish Lift continued to be used as a source of adult American shad and river herring to support monitoring activities and tank spawning. A total of 3,896 adult shad were collected at the Conowingo West Lift. The majority of these were released back into the Conowingo tailrace. Some 1,012 were retained for tank spawning. In addition, 404 American shad were transported and released upstream in conjunction with a fishway efficiency study at York Haven Dam.

Since the completion of fish passage facilities at Holtwood and Safe Harbor in 1997, the Conowingo East Lift has operated in fish passage mode. American shad had access to the Fabri-Dam on the Susquehanna main stem, and Warrior Ridge or Raystown Dams on the Juniata. Portions of large tributaries including Muddy Creek, West Conewago Creek, Conestoga River, Conodoguinet Creek, and Swatara Creek were also accessible to American shad.

During the 2005 spring migration, Conowingo East Lift passed 68,926 American shad while fishways at Holtwood, Safe Harbor, and York Haven passed 34,189, 25,425 and 1,771 American shad, respectively. Only four river herring were passed at Conowingo Dam and none passed at Holtwood.

Juvenile American shad in the Susquehanna River above Conowingo Dam are derived from two sources, natural reproduction of adults passed at the lower river hydroelectric projects, and hatchery produced, marked larvae from the Pennsylvania Fish and Boat Commission’s (PFBC) Van Dyke Hatchery in Pennsylvania. Juveniles occurring in the river below Conowingo and the upper Chesapeake Bay may result from natural spawning below or above dams and hatchery fry stockings either in Maryland or from upstream releases in Pennsylvania.

During the 2005 production season, the PFBC Van Dyke Research Station for Anadromous Fish produced 3.6 million shad larvae which were released in the Susquehanna Basin in Pennsylvania. Larvae were released coinciding with receding flows (Figure 1) between 18 May and 29 June in the following locations and numbers:

Juniata River (various sites) 2,233,750
Susquehanna River (near Montgomery Ferry) 1,001,842
West Branch Susquehanna River 335,083

In addition to the larvae released, approximately 1,250 American shad fingerlings were released at Huntingdon on October 25, 2005. The production goal of 10 million larvae was not met, primarily due to fewer eggs shipped from the Hudson River.

METHODS

Sampling for juvenile American shad was conducted at locations in the Susquehanna River Basin during the summer and fall in an effort to document in-stream movement, out-migration, abundance, growth, and stock composition/mark analysis. Juvenile recoveries from all sources were provided to the PFBC for otolith analysis. Otoliths were analyzed for tetracycline marks to determine hatchery versus wild composition of the samples.

Haul Seining - Main Stem

Haul seining in the lower Susquehanna River was scheduled once each week beginning in mid-July and continuing through October. Fifteen weekly sampling events were planned for 2005, however, high river flow in late October necessitated postponement of the final sampling until November 8. A total of 15 sampling events occurred. Sampling was concentrated near the Columbia Borough boat launch since this location proved very productive in past years. Sampling consisted of 6 hauls per date beginning at sunset and continuing into the evening with a net measuring 400 ft x 6 ft with 3/8 in stretch mesh.

Holtwood Dam, Peach Bottom APS, and Conowingo Dam

Sampling at the Holtwood Dam inner fore-bay began on 13 September and continued every third day through November 2005. A total of 30 sampling events was planned for 2005. By late November, it was apparent that the out-migration was over. Therefore, the program was terminated after completion of 27 of the 30 scheduled events.

Sampling at the Holtwood Dam inner fore-bay was conducted using a fixed 8-ft square lift-net. Sampling began at sunset and consisted of 10 lifts with a 10-minute interval between lift cycles. The lift-net was placed on the north side of the coffer cell in the inner fore-bay. A lighting system was used to illuminate the water directly over the lift-net similar to that employed in previous years.

A comprehensive program to monitor intake screens for impinged alosines at Peach Bottom Atomic Power Station was conducted in 2005. Sampling was conducted on a 24-hour basis, twice per week from Sept. 1 to Dec. 31. When shad were collected in the Holtwood lift net during the previous week, an additional (third) sample was collected the following week at Peach Bottom. A total of 50 samples were collected during September through December. Conowingo Hydroelectric Station’s cooling water intake screens were also sampled for impinged alosids twice weekly from 3 October to 8 December for a total of 16 samples.

Susquehanna River Mouth and Flats

Maryland DNR sampled the upper Chesapeake Bay using haul seines in the summer and fall.

Disposition of Samples

Sub-samples of up to 30 juveniles per day were used for otolith analysis. Samples of shad from most collections were returned to PFBC's Benner Spring Fish Research Station for analysis of tetracycline marks on otoliths. Otoliths were surgically removed from the fish, cleaned and mounted on slides, ground to the focus on the sagittal plane on both sides, and viewed under ultraviolet light to detect fluorescent rings indicating tetracycline immersion treatments.

RESULTS

Haul Seining - Main Stem

A total of 23 juvenile American shad were captured by haul seine resulting in a Geometric Mean Catch-Per-Unit-Effort (GM CPUE, individual haul) of 0.16 (Tables 1 and 2). Juvenile American shad were captured from July 20 to October 20 with no apparent peak in abundance. Two of the 5 shad captured on August 2 were of hatchery origin. All other shad captured by haul seine were wild in origin. Table 3 lists weekly catches of American shad by haul seine from 1989 to 2005. Catches generally peaked in August and September, except in 1989 and 1992 when catches peaked in July, and in 2005 when there was no peak.

Table 1

Table 2

Table 3

Holtwood Dam, Peach Bottom APS, and Conowingo Dam

Lift-netting at the Holtwood Dam inner fore-bay resulted in 200 juvenile American shad captured in 300 lifts (Table 4). All shad were captured between October 25 and October 31, with 171 captured on October 28. Geometric Mean CPUE (individual lift) was 0.10 while GM CPUE (combined daily) was 0.15 (Table 5). Historical weekly catches peaked in October, except in 1985, 1997, 2000, and 2001 when catches peaked in November (Table 5). Four alewife were captured by lift-net on 28 October 2005.

Table 4

Table 5

Peach Bottom intake screens produced 135 juvenile American shad and 29 alewives (Table 7).

Table 7

Cooling water strainers at Conowingo produced 25 American shad, collected between 21 October and 7 November (Tables 8 and 9).

Table 8

Table 9

Susquehanna River Mouth and Flats

In 2005, 115 juvenile American shad were captured at seven permanent sites by Maryland DNR’s juvenile finfish haul seine survey during 42 hauls, and 129 juvenile American shad were captured at the auxiliary sites during 30 hauls (Table 10).

Table 10

Otolith Mark Analysis

Results of otolith analysis are presented in Table 11. A total of 368 juvenile American shad were collected in haul seines, lift nets, Peach Bottom intakes and Conowingo strainers. Of the 230 specimens evaluated for hatchery tags, 58.5% were wild and 41.5% were hatchery.

Table 11

DISCUSSION

Spring river conditions for the Susquehanna River Basin during 2005 could be characterized by relatively stable flows with two minor peaks in mid-June (Figure 1) followed by drought conditions until early November (Figures 2 and 3). Water temperatures at Conowingo Dam were less than 60F from 15 April to 10 May, jumped from 62 to 66F from 11 May to 16 May, remained above 66F until 31 May, and then remained above 70F until the fish lift closed for the season on 8 June. Stable flows and cool temperatures extended the length of the spawning season and contributed to an increase in eggs delivered to the hatchery from Conowingo tank-spawning.

Figure 1

Figure 2

Figure 3

The relatively stable flows in the watershed during the 2005 stocking season should have promoted good survival of larvae (Figure 1). This is in contrast to 2004, when many of the stocking events were followed by increases in flow resulting in conditions that were not optimal for larval survival.

Fish passage at Holtwood was better than average with 50% passage, based on counts at Conowingo and Holtwood (mean = 30%). Fish passage at Safe Harbor was equal to the long-term mean of 74%, based on counts at Holtwood and Safe Harbor. Fish passage at York Haven (7%) was lower than the average of 14%, based on counts at Safe Harbor and York Haven. Some 1,772 shad were counted passing the York Haven Dam fishway.

Abundance – Main Stem

Comparison of relative abundance of juvenile alosids in the Susquehanna River from year to year is difficult due to the opportunistic nature of sampling and wide variation in river conditions, which may influence catches. In 2005, haul seine and lift net CPUE were among lowest ever recorded.

GM CPUE for haul seine (both individual lifts, and combined daily lifts, Table 2) was the second lowest value ever recorded for that gear type since 1990. GM CPUE for lift net collections (Table 5) in the Holtwood Dam forebay was slightly more encouraging, but was still an order of magnitude lower than in 1985-1988, 1990, 1993, 1995 or 2001. Juvenile shad abundance has been below normal for four consecutive years, a disturbing trend that may impact fish passage during 2006 to 2010. In 2002, problems at the Van Dyke Hatchery resulted in release of comparatively few healthy larvae. In 2003 and 2004, high river flows had a negative impact on survival of stocked hatchery larvae and on fish passage efficiency. The apparent poor catch rates for juvenile shad in 2005 may have been due, in part, to fewer larvae stocked.

Stock Composition and Mark Analysis

Hatchery contribution varied between sites and collection dates. Contribution of hatchery fish from Columbia, Holtwood, Peach Bottom and Conowingo was 9%, 41%, 53% and 21%, respectively. Hatchery contribution varied on a daily basis. For example, on 26 October, hatchery fish constituted 44% of the catch at Peach Bottom. One day later, on October 27, hatchery contribution was 64%.

SUMMARY

  • Juvenile American shad were successfully collected by haul seine at Columbia, in lift nets at Holtwood, in cooling water intakes at Peach Bottom Atomic Power Station, and in strainers at Conowingo Dam.
  • Haul seine GM CPUE (combined daily lifts) of 0.24 was the second lowest recorded for that gear type since 1990.
  • Lift-net GM CPUE (combined daily lifts) of 0.15 was among the lowest recorded for that gear type since 1985.
  • Otoliths from the four sites combined were 42% wild and 58% hatchery.
  • Fewer eggs were delivered to the Van Dyke Hatchery, resulting in decreased production of hatchery larvae, and decreased production of juvenile American shad in the Susquehanna River basin.

ACKNOWLEDGMENTS

Normandeau Associates (Drumore, PA) was contracted by the PFBC to perform juvenile collections. Many individuals supplied information for this report. Ken Woomer and Coja Yamashita, PFBC seasonal employees, processed shad otoliths.


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