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Research Project: Toxicity Testing of Weed Biological Control Agents as Food for Fish of Concern in the Sacramento-San Joaquin River Delta

Location: Invasive Species and Pollinator Health

Project Number: 2030-22300-032-013-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Nov 25, 2020
End Date: Nov 26, 2022

The objective of this work is to determine if threatened or endangered fish are negatively influenced by the consumption of the alligatorweed flea beetle (Agasicles hygrophila). As part of the ongoing Biological Opinion, the United States Department of Agriculture (USDA) and the Department of Parks and Recreation, Division of Boating and Waterways (DBW) work collaboratively to implement and improve weed control in the Sacramento-San Joaquin River Delta. Implementing biological control of alligatorweed requires contracting with the UC Davis’ Aquatic Health Program Laboratory (AHPL) to conduct feeding studies using rainbow trout (Oncorhynchus mykiss) and delta smelt (Hypomesus transpacificus) when provided the alligatorweed flea beetle as a diet. The current DBW Biological Opinions from the US Fish and Wildlife and NOAA Fisheries approves the release of the water hyacinth weevil (Neochetina eichhorniae) and plant hopper (Megamelus scutellaris) currently but it is our intention to add additional species to include the alligatorweed flea beetle. The intent of this agreement is to acquire additional data from the AHPL to satisfy regulatory agencies and ultimately to improve control of floating aquatic vegetation through the existing DBW Biological Opinion process. The USDA and DBW will cost share the expenses of this work 50:50. An agreement will transfer funds from DBW to the USDA, who will match the funds and manage a subcontract with the AHPL.

Toxicity testing will be conducted from November 2019 through April 2020, based on availability of test subjects. Toxicity test duration of toxicity tests will include both a 96-hour acute assessment and a chronic 7 day test for both fish species. This study will consist of three treatments: 1) fish fed with alligatorweed flea beetle A. hygrophila, 2) fish fed with regular diet (to be used as negative control), and 3) a fasting group that is not going to receive any feed for the duration of the experiment. With a 9:00 am initiation time, fish will be fed three times daily: 1) 10:00, 2) 12:00, and 3) 14:00, with fish sampled at 15:00 at termination. The sampled fish will be individually wrapped in foil and flash frozen in liquid nitrogen on-site. Sampled fish will be measured (weight and length) and dissected at the UC Davis VM3B lab. In addition to gut content analysis, liver from each fish will be fixed in formalin for histological evaluation of liver glycogen and pathology, and muscle will be preserved at -80°C for measuring RNA/DNA ratio.