ANS Aquatic Nuisance Species Volume 3 No. 4 November 1999 FRESHWATER DIGEST FOUNDATION Providing current information on monitoring and controlling the spread of harmful nonindigenous species. Egeria Invades the Sacramento-San Joaquin Delta By Lars W.J. Anderson ust when state and federal water resource managers in water hyacinths eventually led to a state-funded control program California felt they had the “bad” actor - Hydrilla verticillata- that has effectively kept it at low levels. Although it’s not certain J(family Hydrocharitaceae) eradicated, another invasive rela- when egeria got its start, populations really began to expand in the tive, egeria (Egeria densa) has recently spread to one of the state’s mid-1990s, shortly after the end of a six year drought period. It most vital and sensitive ecosystems. For almost 25 years since may be that a combination of the low runoff from the Sierra hydrilla was discovered in the Golden State, an effective eradica- Nevada Mountains and clearer, warmer water conditions facilitat- tion program has kept it in check, and importantly, out of the mas- ed the expansion. It is also likely that the removal of water sive delta created by the Sacramento and San Joaquin rivers, just hyacinth “cover” provided more suitable habitat (particularly “upstream” from San Francisco Bay. This massive waterway is available light) for egeria. Whatever the reasons, current surveys not only a critical habitat for fish and wildlife, including the by the California Department of Boating and Waterways (CBWW) endangered Delta Smelt; it is also the water life-line for some 23 indicate that egeria occupies more than 3,000 acres at varying den- million thirsty southern Californians, and much of the state’s sities (see Figure 1). The biomass (standing crop) in some of the multibillion-dollar agricultural economy. It’s easy to see the most heavily populated sites ranges from 1 to 2 kg/ sq. meter, or importance of keeping this system healthy and free of intruding nearly 9 tons per acre. pests that can interfere with critical habitats, food webs, and water California is not alone in trying to cope with egeria. Several delivery. Unfortunately, there is no eradication tool or program other western states including Oregon and Washington, as well as for egeria. southeastern areas of the U.S., have varying levels of infestations. The saga of noxious aquatic weeds in the Delta actually Since this plant is freely available in aquarium shops and specialty began when water hyacinth was introduced in the early 1900s and nurseries in most states, including California, it’s not surprising subsequently created huge problems in 1983. The explosion of that egeria has been introduced and become widespread. Egeria continued on next page Ruffe - a Problem or Just a Pest? By Raymond M. Newman he ruffe (Gymnocephalus cernuus L., to over 150,000 eggs during spawning. Tformerly Acerina cernuua), a small This high reproductive potential often In This Issue: perch-like fish native to Europe and Asia, results in abundant but “stunted” popula- was first found in North America in the St. tions with smaller maximum sizes (Popova Louis River Harbor, at the western end of et al. 1998). Nuisance Notes from Western Lake Superior, in 1986 (Pratt et al. 1992). Ruffe are benthic feeders (Ogle 1998), Regional Panel on ANS . 41 They most likely arrived in ballast water relying on small benthic invertebrates that from Europe, probably from somewhere in live in lake and river bottoms. Minnesota DNR Tests the Use of the Danube basin (Stepien et al. 1998). In Chironomids are often a dominant compo- 2,4-D in Managing Milfoil . 42 Europe, ruffe, though often abundant, are nent of the ruffe diet. Like perch and wall- of little sport and commercial value due to eye, ruffe are well adapted to dark and tur- Upcoming Meetings . 46 their small size (rarely larger than 25 cm or bid conditions such as those found in more 10” and more commonly less than 15 cm) eutrophic waters. Ruffe possess a well- Great Lakes Update . 47 and spiny body. Ruffe are prolific and developed tapetum lucidum, a layer of have a high reproductive potential; they reflecting plates behind the retina, that may spawn two to six times during the enables them to feed in low light to dark year and females can produce from 10,000 conditions. In addition, ruffe have a highly Ruffe continued on page 44 Aquatic Nuisance Species Digest Egeria continued from previous page Percent of Egeria Area Coverage 0.10 - 10.0 Freshwater Foundation Staff 10.0 - 20.0 Jeanne C. Prok, Editor 20.0 - 30.0 Gene B. Hansley, Managing Editor 30.0 - < Ann Conrad, Program Director Editorial Board Lars W. J. Anderson, Ph.D. University of California–Davis John W. Blake, Ph.D. New York Power Authority (retired) Allegra Cangelosi Northeast-Midwest Institute James T. Carlton, Ph.D. Williams College–Mystic Seaport William Culpepper SePRO Corporation Thomas Fritts, Ph.D. USGS–Biological Resources Division Katherine Glassner-Shwayder Great Lakes Commission Douglas A. Jensen University of Minnesota Sea Grant John Kahabka New York Power Authority Stuart C. Leon, Ph.D. U.S. Fish and Wildlife Service Leo G. Nico, Ph.D. USGS–Biological Resources Division Jay Rendall Minnesota Department of Natural Resources William E. Roper, Ph.D. U.S. Army Corps of Engineers Edwin Theriot, Ph.D. U.S. Army Corps of Engineers Janet Thompson 1 2 3 4 USGS–Water Resources Division Randy Westbrooks, Ph.D. MILES U.S. Department of Agriculture Figure 1. Enlarged view showing the Sacramento-San Joaquin Delta, California. The Direct questions and comments about ANS shaded areas show the locations of Egeria densa infestations: darkest shading indicates the Digest to: Jeanne Prok, Freshwater Foundation, most abundant populations. (Courtesy of Califorina Department of Boating and Gray Freshwater Center, 2500 Shadywood Road, Waterways) Navarre, MN 55331; (888) 471-9773; e-mail: [email protected]. Aquatic Nuisance Species Digest (ISSN 1083- Impacts Caused by Egeria 8864) is produced by the Freshwater Foundation, a public nonprofit foundation whose mission is to The first public alarm was sounded in 1994 by marina operators and by some of the com- pursue the sustainable use of freshwater resources mercial vessel operators in the Delta. Large stands of egeria were beginning to block access to through education, conferences, publications and boat slips, fishing and swimming areas, and even some boats had begun to experience mechani- research. Funding for this issue of ANS Digest cal problems. Egeria wraps up on propellers, rudders, keels, and the smaller fragments clog came from the National Sea Grant Program through the Minnesota Sea Grant Program. cooling systems, which results in burned-out engines. Some interference with irrigation pumps Minnesota Sea Grant is a statewide program that was noted as well. In some areas, property values became affected by the persistent masses of supports research and public education related to egeria in what were formerly open and aesthetically pleasing delta waterways. Finally, enough Lake Superior and Minnesota’s inland lakes. It is waterfront property owners and marina owners reacted. The state legislature was compelled to part of the National Sea Grant Program, which enact State Assembly Bill 2193 in 1997, which added egeria control to the water hyacinth con- supports research and outreach in 31 coastal and Great Lakes states and territories. trol program responsibilities of the Department of Boating and Waterways. © 1999, Freshwater Foundation. Other impacts of egeria are less obvious. These include the displacement of native ATMOSPH ND ER A IC IC pondweed species (Potamogeton spp.), impairment of access for waterfowl, and severe shading N A A D E M I C N O I S L T of the upper water column. The dense upper “canopy” formed by egeria blocks light that A R N A O T I I O T A N N would normally be available to the microscopic algae (phytoplankton). The lack of primary U E S C D R E E P M production by the phytoplankton inhibits fisheries production since these organisms form the AR M TME F CO NT O base of the food chain. Some effects remain unclear. For example, how does egeria alter nor- Egeria continued on next page 38 Aquatic Nuisance Species Digest Nomember 1999 Volume 3, No. 4 Egeria continued from previous page mal spawning habitat for salmon, bass and, importantly, the endan- Bay/Delta. This of course has not prevented the invasion and establish- gered native, Delta Smelt? Presumably, prior to the intrusion by ege- ment of many other exotic plants and animals that thrive in saline con- ria, native fish had adequate habitat provided by native aquatic plant ditions! The Bay/Delta area is now home to over 200 invasive plant species. and animal species. In addition to negative impacts on wildlife, egeria acts like a filter and accelerates deposition of suspended materials. Each year, hun- dreds of tons of organic and inorganic materials are carried down- stream with the seasonal snowmelt. In areas where egeria has formed dense stands, the water is slowed and materials that are normally trans- ported and spread throughout the Delta and upper Bay become entrapped and settle. The net result is localized heavy organic loading of the sloughs; these shallow areas will have to be dredged eventually. Taking a broader perspective, the persistence and continued spread of egeria in the Delta will also greatly increase the opportunity for the exotic plant to invade lakes, ponds, and streams because thou- sands of boaters can inadvertently carry hitch-hiking fragments on their trailers, boats, and motors. Since the plant can survive for sever- al days, each boat and trailer becomes a dispersal agent.