San Francisco Estuary Institute (SFEI) | December 1st, 2009
Summary
In 2009, California Department of Fish and Game Commission listed longfin smelt (Spirinchus thaleichthys) as threatened, and NOAA formally adopted “take” provisions f
In 2009, California Department of Fish and Game Commission listed longfin smelt (Spirinchus thaleichthys) as threatened, and NOAA formally adopted “take” provisions for green sturgeon (Acipenser medirostris Ayres). These changes in the management status, and associated permitting issues, have prompted renewed interest among [long term management strategy] LTMS participants in the management of these native fish. In response, LTMS held symposia on December 2 and 3, 2009, to review and consider the science, management, and policy related to dredging activities and these species. A primary stressor to both species is reduction of appropriate habitat, due to water diversion activities and other basin-scale modifications in water flow. Local studies of dredging have shown little evidence of direct entrainment for either species, and the frequency of encounter with sites of dredging activity is likely to be very low.
Nevertheless, spatial and temporal patterns of population movements and reproductive activity vary from year to year, making it difficult to employ an environmental work windows approach. Available information is limited on other direct effects of dredging, including sediment contamination, habitat modification, and underwater noise. Indirect effects due to maintenance of active navigation channels pose potential concerns. In particular, introduction of invasive species, and mortality due to propeller strikes, both warrant attention.
As a follow up step to the symposia, we recommend that LTMS host a workshop targeted towards specific LTMS management needs for green sturgeon and longfin smelt. The workshop should include LTMS participants, the scientists that presented at the symposium, and dredging operators, and could focus on the integration of current research findings into tools that would be useful for managers. Appropriate tools for consideration include predictive or descriptive models of species distribution, and of potential impacts of various dredging activities. There should also be consideration of management approaches that broadly address the primary ecosystem-level stressors for green sturgeon and longfin smelt, rather than employing small scale project-level mitigation. In particular, an integrated regional restoration and monitoring program may be the most effective approach to improve the health of the species.