Desmond J. Maynard

Vulnerability of Marked Age-0 Steelhead to a Visual Predator

Abstract The assumption that marking does not alter the vulnerability of fish to a visual predator was examined. Similar numbers of age-0 steelhead Oncorhynchus mykiss were tagged with binary-coded-wires, tagged with passive integrated transponders, freeze branded, marked with fingerling tags, or left unmarked. All were subjected to age-1 steelhead predators for 24 h in 2.4-m-diameter circular tanks filled with clear well water. Twice as many marked as unmarked age-0 steelhead prey were eaten. There was no significant survival difference among the four marked treatment groups, which suggested that in the laboratory the trauma associated with marking is more important than mark type. We conclude that marking may effect postrelease survival and recommend that mark–recapture experiments be used to empirically determine and correct for differences in survival of marked and unmarked fish.

Introduction to a Special Section: Hatcheries and Management of Aquatic Resources (HaMAR)—Considerations for Use of Hatcheries and Hatchery-Origin Fish

C

Methods and Accuracy of Sexing Sockeye Salmon Using Ultrasound for Captive Broodstock Management

AbstractUltrasound has been widely used to noninvasively examine the internal anatomy and reproductive status of many fish species. Since 2003, ultrasonography has been an integral part of broodstock management for Endangered Species Act–listed endangered Redfish Lake Sockeye Salmon Oncorhynchus nerka. Initial ultrasound screenings for each years broodstock were conducted 3 to 4 months prior to anticipated maturation, before external signs of maturation developed. In keeping with the natural life history of these fish, this permitted the separation of nonmaturing fish from maturing fish so the immature fish could maintain feeding and growth. It also permitted maturing seawater-reared fish to be transferred to freshwater for final maturation. Designing a spawning matrix to maintain genetic diversity requires knowledge of the sex of each fish before spawning. Approximately 1 month prior to spawning, a second ultrasound was performed to verify sex identification and thus ensure the accuracy of the spawning ...

A Study to Determine the Biological Feasibility of a New Fish Tagging System : Annual Report 1990-1993.

In 1983, the National Marine Fisheries Service (NMFS) began a multiyear cooperative research program with the Bonneville Power Administration (BPA) to evaluate a new miniaturized identification system that could be used with salmonids. The system is referred to as the passive-integrated-transponder (PIT) tagging and interrogation system. The program has focused on determining the effects of PIT tags on juvenile and adult salmonids, as well as the development and evaluation of tagging and interrogation methods. Earlier results of the program have been reported in annual reports and journal articles cited in this report. This report covers the work per formed from 1990 through 1993. For convenience, the report is divided into three sections: (1) Interrogation and separation systems at Columbia River Basin dams; (2) Systems development and evaluation; and (3) Information and technology transfer.