Monitoring Relative Abundance of American Shad in Virginia's Rivers 2001 Annual Report

J.E. Olney
2002
Executive Summary · A staked gill net was set and fished two days per week on the James, York and Rappahannock rivers in the spring of 2001. This was the fourth year of monitoring in a stock assessment program for American shad that was initiated in spring 1998. The primary objective is to establish a time series of catch rates that can be compared to historical catch rates recorded in logbooks voluntarily submitted by commercial fishers prior to the imposition of the current moratorium. The
more » ... moratorium. The monitoring effort provides information on the current status of shad stocks relative to conditions prior to the moratorium dating to 1980. In the case of the York River, monitoring may allow assessment of current status relative to conditions during the 1950's. · Sampling occurred for 13 weeks on the James River (18 February -14 May 2001) and 12 weeks on the York and Rappahannock rivers (25 February -21 May 2001). A total of 1,211 female American shad (1,705 kg total weight) was captured. The 2001 catch was larger than the catch in 1999 (575 females weighing 796 kg) and 2000 (904 females weighing 1,299 kg). · Total numbers of females in 2001 were highest on the York River (n= 677). Equal numbers of females were captured on the James and Rappahannock rivers (n= 267). As in previous years, total numbers of males were low on all rivers (York, 43; James, 20; Rappahannock, 61). The total weight of all males captured was 144 kg. · Based on age estimates from scales, the 1996 and 1997 year classes of female American shad were the most abundant on the James and Rappahannock rivers with age-specific seasonal catch rates exceeding 0.01 kg/m. On the York River, the 1995, 1996 and 1997 year classes were the most abundant (age-specific seasonal catch rates exceeding 0.01 kg/m). Total instantaneous mortality rates of females calculated from age-specific catch rates were: York River, 1.07; James River, 1.35; and Rappahannock River, 1.29. · Otoliths of all American shad captured in staked gill nets on the James River were scanned for hatchery marks and otoliths of 186 specimens captured on the York River were scanned. The proportion of the sample with hatchery marks on the James and York rivers was 40.2 % (103 of 256 fish) and 4.8 % (9 of 186 fish), respectively. In 1998 and 1999, prevalence of hatchery fish on the James River was low (4-8 %). The evidence suggests that the increase in catch rates observed on the James River in 2000 and 2001 is due to the first large-scale influx of mature hatchery fish since the restoration program began. · Otoliths of 288 juvenile American shad collected during pushnet cruises in 2001 on the Pamunkey River were scanned for hatchery marks. The proportion of the sample with hatchery marks was 6.6 % (19 of 288 fish). By comparison, the proportion of the 2000 sample with hatchery marks was 7.0 % (7 of 100 fish) and the proportion with hatchery marks in 1999 was 6.0 % (3 of 50 fish). · The geometric mean catch of juvenile American shad (based on weekly summer pushnet surveys) was 55.9 on the Mattaponi River and 9.8 on the Pamunkey River. The combined 3 integrated catch index for the York system (both the Pamunkey and Mattaponi rivers) was the second highest value observed thus far in the time-series average (average, 1,367.5; 2001 value, 5,502.6). · Twenty-six species of fishes were taken as by-catch in the staked gill net monitoring gear for a total of 23,636 specimens. The total number of striped bass captured was 3,021 (James River, n= 1,093; York River, n= 889; Rappahannock River, n= 1,039) . Live striped bass captured in the gear were counted and released. The proportions of dead striped bass on each river were: James River, 47.9 %; York River, 38.0 %; and the Rappahannock River, 40.9 %.
doi:10.21220/v5pk73 fatcat:furyyekvknbsrovwhocvgtrbei