Brian Watkins

Migratory Behavior of American Shad in the York River, Virginia, with Implications for Estimating In-River Exploitation from Tag Recovery Data

Abstract Tagging of American shad Alosa sapidissima may alter their migratory behavior, causing some tagged individuals to cease or delay the spawning run. In a tag recovery study designed to assess fishery impacts, this altered behavior would reduce the number of tagged fish available to the target fishery and would bias estimates of exploitation and fishing mortality rates. To investigate this possibility, we fitted 29 prespawning adults with acoustic tags and released the fish into the middle reaches of the York River, Virginia. Movements of individuals were remotely monitored at three hydrophone stations: (1) 7 river kilometers (rkm) downriver of the release site; (2) on the Mattaponi River, 48 rkm upriver of the release location; and (3) on the Pamunkey River, 56 rkm upriver of the release location. Almost half of the fish were apparently affected by capture, handling, and tagging, as they either abandoned their migration or delayed their upstream movements. The movements of some fish appeared to be ...

Evaluating the Current Status of American Shad Stocks in Three Virginia Rivers

Abstract Directed commercial fisheries for American shad Alosa sapidissima in the primary Virginia tributaries of the Chesapeake Bay have been under moratorium since 1994. Monitoring of adult American shad within these rivers has been ongoing since 1998 through a cooperative program involving commercial fishers. The monitoring program is designed to mimic traditional commercial fishing practices so that stock status can be inferred by comparing contemporary catch-per-unit-effort levels with those derived from historic logbooks. In this paper, we present analyses of the available monitoring and historic catch rate data along with updated stock status information for American shad in the James, York, and Rappahannock rivers. Two analytical methods were used to derive annual indices of relative abundance; both methods yielded very similar patterns for each river system. Comparisons of contemporary and historic indices of relative abundance suggest that American shad in the James and York rivers continue to persist at low levels of abundance. Measures of stock abundance in the Rappahannock River have been higher than the logbook reference value for much of the monitoring period. However, current moratoria and restoration strategies, which include hatchery releases of fry, the removal of obstructions blocking spawning and nursery habitat, and reductions in bycatch from other fisheries, should continue into the foreseeable future.

Occurrence of Juvenile Paralichthys lethostigma (Southern Flounder) in Tributaries of Chesapeake Bay

Abstract Paralichthys lethostigma (Southern Flounder) inhabits the continental shelf and estuarine waters of the Gulf of Mexico and the east coast of the North Atlantic, from peninsular Florida to Albemarle Sound in North Carolina. Between 30 May and 20 August 2012, we collected 15 juvenile (71–192 mm) Southern Flounder in fyke nets in the Mattaponi River, a tributary of the York River, in southeastern Virginia. This is the first known documentation of juvenile Southern Flounder in any tributary of Chesapeake Bay. We confirmed our identification of the specimens as Southern Flounder morphologically and genetically by counting gill rakers and sequencing cytochrome oxidase subunit I, respectively.

Monitoring Relative Abundance of American Shad in Virginia Rivers 2008 Annual Report

Tagging American shad (Alosa sapidissima) may alter migratory behavior, causing some tagged individuals to cease the spawning run. In a tag-recovery study designed to assess fishery impacts, this altered behavior would reduce the number of tagged fish available to the target fishery, and result in biased estimates of exploitation rate and fishing mortality. To investigate this possibility, 29 pre-spawning adults were fitted with acoustic tags and released in the middle reaches of the York River, Virginia. Movements of individuals were remotely monitored at three hydrophone stations; one seven km downriver of the release site and one on each of the spawning tributaries (Mattaponi and Pamunkey rivers), 48 and 56 km upriver of the release location. Almost half of the fish were apparently affected by capture, handling and tagging since these individuals either abandoned the migration or were delayed in their upstream movements. Movements of some fish appeared to be unaffected by capture since they were not detected at the downriver station and were detected on the spawning grounds 2-5 days after release. Eighteen fish remained on the spawning grounds for 17-51 days (average residency, 34.4 days) and were last detected at the downriver location, presumably migrating seaward. Residence time on the spawning grounds declined with successive releases. We were unable to account for eight fish that migrated to the spawning grounds but were not detected again. Fifteen shad (57% of the total that migrated) originally selected spawning grounds on the Mattaponi River; the remaining fish selected the Pamunkey River. One fish resided for several weeks on both tributaries, suggesting some mixing of spawning locations. We conclude that tagging protocols designed to measure the impacts of fishing on American shad should include telemetry to assess altered migratory behavior. Analytical methods to assess fishing mortality for American shad require modification. (2) Estimating offshore stock composition of American shad (Alosa sapidissima) using mark-recovery data (submitted to North American Journal of Fisheries Management, 4/05) John M Hoenig, Robert J. Latour, and John E. Olney Abstract Information on the stock composition of mixed-stock fisheries is often needed to develop management regulations for anadromous fishes. Although several methods can be used to infer stock composition, marking studies have long been identified as a promisingInformation on the stock composition of mixed-stock fisheries is often needed to develop management regulations for anadromous fishes. Although several methods can be used to infer stock composition, marking studies have long been identified as a promising approach. We explore the utility of using marking to determine the stock composition of mixed-stock fisheries of American shad (Alosa sapidissima) along the east coast of North America. Our analysis focuses on the impact of the Virginia coastal ocean fishery on the American shad produced in the James and Pamunkey rivers, Virginia, and our results suggest that this fishery harvested relatively small proportions of these stocks. The method requires that juvenile shad be uniquely marked in the rivers in their first year of life. The proportion of the offshore catch from a particular river is inferred by comparing the proportion of the offshore catch with marks from the river with the proportion of the fish returning to the river with marks. We also examine the usefulness of tagging adult fish on the offshore fishing grounds and show that if tagging only occurs in a single offshore location, information on stock composition cannot be obtained. In contrast, if tagging occurs in at least k offshore locations that each reflects a unique composition of k stocks, it is theoretically possible to infer stock composition. However, under this latter scenario, the information obtained is not likely to be reliable due to impracticalities associated with implementing the study design. (3) Comparing historical catch rates of American shad in multifilament and monofilament nets: A step towards setting restoration targets for stocks under moratorium in Virginia (submitted to North American Journal of Fisheries Management, 3/05) Kristin L. Maki, John M. Hoenig, Dennis M. Heisey, John E. Olney Abstract Recreational and commercial harvest of American shad in Virginia waters of the Chesapeake Bay and its tributaries has been prohibited since 1994. The Shad and River Herring Management Plan requires that Virginia develop restoration targets for its shad populations but estimates of their size are not available and there is little information about historic population levels. Thus, establishing restoration targets based on population size is problematic. A current spawning stock monitoring program yields catch rate information that is comparable with historic catch records recorded in commercial logbooks from the 1950s and the 1980s. However, multifilament gill nets were used in the 1950s and monofilament nets were used in the 1980s (as well as in the current monitoring program). A Latin square design was employed to test the differences in relative fishing power of the two gear types over two years of seasonal sampling on the York River, Virginia. Estimates suggest that monofilament nets are roughly twice as efficient as the multifilament nets. Reported catch rates in the 1950s and 1980s are roughly equivalent. However, when adjustments are made for differences in fishing gear, catch rates for the 1950s are twice as high as during the 1980s. These results provide valuable information for setting restoration targets for Virginia stocks of American shad.Recreational and commercial harvest of American shad in Virginia waters of the Chesapeake Bay and its tributaries has been prohibited since 1994. The Shad and River Herring Management Plan requires that Virginia develop restoration targets for its shad populations but estimates of their size are not available and there is little information about historic population levels. Thus, establishing restoration targets based on population size is problematic. A current spawning stock monitoring program yields catch rate information that is comparable with historic catch records recorded in commercial logbooks from the 1950s and the 1980s. However, multifilament gill nets were used in the 1950s and monofilament nets were used in the 1980s (as well as in the current monitoring program). A Latin square design was employed to test the differences in relative fishing power of the two gear types over two years of seasonal sampling on the York River, Virginia. Estimates suggest that monofilament nets are roughly twice as efficient as the multifilament nets. Reported catch rates in the 1950s and 1980s are roughly equivalent. However, when adjustments are made for differences in fishing gear, catch rates for the 1950s are twice as high as during the 1980s. These results provide valuable information for setting restoration targets for Virginia stocks of American shad. (4) Testing the validity of Cating’s criteria for age estimation of American Shad from the Lehigh River (submitted to Fisheries, 2/05) R. McBride, M. Hendricks and J. Olney Abstract Cating’s (1953) method for ageing American shad in the Hudson River using scales has been the standard for over 50 years, largely because Judy (1961) validated the method for ages 4-6 in the Connecticut River. There have been no other validation studies. To test the method on older fish in another river, we assessed precision, accuracy, and bias of 13 experienced biologists using 53 known-age fish from the Lehigh River. Biologists had reasonably good precision but accuracy was poor. Percent accuracy was highest for age 3-6 (33.7-48.5%) but dropped for age-7 (12.1%) and age-8 (3.9%). There was substantial variation among readers and the inaccuracies were biased. Ages of younger fish were overestimated while those of older fish were underestimated. Cating’s method may not be applicable to all American shad stocks. Thus, we recommend caution in applying agebased assessment techniques to stocks that lack age validation across all ages.Cating’s (1953) method for ageing American shad in the Hudson River using scales has been the standard for over 50 years, largely because Judy (1961) validated the method for ages 4-6 in the Connecticut River. There have been no other validation studies. To test the method on older fish in another river, we assessed precision, accuracy, and bias of 13 experienced biologists using 53 known-age fish from the Lehigh River. Biologists had reasonably good precision but accuracy was poor. Percent accuracy was highest for age 3-6 (33.7-48.5%) but dropped for age-7 (12.1%) and age-8 (3.9%). There was substantial variation among readers and the inaccuracies were biased. Ages of younger fish were overestimated while those of older fish were underestimated. Cating’s method may not be applicable to all American shad stocks. Thus, we recommend caution in applying agebased assessment techniques to stocks that lack age validation across all ages. (5) Six Fish and 600,000 Thirsty Folks A Fishing Moratorium on American Shad Thwarts a Controversial Municipal Reservoir Project in Virginia, USA (submitted to American Fisheries Society Fisheries Congress book editor, 3/04) Olney, J.E., C.H. Hershner, D.M. Bilkovic, H. Wang, L.M. Varnell, and R.L. Mann