4/30/2023 0 Comments California freshwater fishWe think there is also a need to focus analyses at regional scales, because studies at continental or global scales tend to yield results with limited predictive ability ( Gido and Brown 1999, Lockwood 1999, Ruesink 2005). In particular, they argue for the need to analyze data on failed invasions. Kolar and Lodge (2001) argue, however, that quantitative approaches (including meta-analysis of diverse sources of information) can produce useful predictions. Thus, to make predictions useful for the management and control of alien species, scientists need to understand the nature of invaders, the invasion process, and the impact of invasions, and to communicate that knowledge effectively.īecause “any species can invade and any environment can be invaded”( Moyle and Light 1996), a search for generalities that would be useful for predicting the success of potential invaders may be futile. Many harmful alien fishes, for example, are also favorite food and game fishes. Efforts to prevent the spread of unwanted fish and other organisms, however, are still small compared with the size of the problem ( Meyerson and Reaser 2003), in part because policymakers and the public often fail to appreciate the seriousness of the invasions. Invasions by alien species also have high ecological and economic costs. Because many fish species are widely introduced, there is concern among scientists and managers over the homogenization of freshwater fish faunas worldwide (McKinney and Lockwood 1999, Marchetti et al. The best-documented invaders in these systems are fishes. Streams, lakes, and estuaries are among the most highly invaded ecosystems in the world in many of them, alien organisms are now a significant part of the biota ( Cohen 2002). The difficulty of predicting the invasion success of alien species points to the need to allow only introductions that have proved to be nonharmful and to take quick action to prevent the spread of new invaders. The factors that best predict invasion success are (a) a history of successful establishment outside the species' native range (b) characters that promote success at multiple stages of the invasion process (e.g., high physiological tolerance) (c) invaded habitat that more or less matches the alien's native habitat (d) high fish species richness, including other alien fishes and (e) propagule size exceeding 100 individuals. We found no set of characters that predicted success for all fish invasions, although some characters increase the probability of success. Our analyses show that different characteristics of alien fishes are important at different stages of the invasion process. For more information on giving to this and other funds through your tax form go to bit.ly/3i1RoaI.įor more information on otters visit CDFW’s Sea Otter Stranding Response web page at bit.ly/3KGna9v.The location, size, and geography of California, combined with extensive knowledge of successful and failed fish invasions, provide an unusual opportunity to test predictors of invasion success. The public can help by donating to this fund through the Voluntary Tax Contributions section on their California State Income Tax Form 540, line 403. Investigation of sea otter mortality is supported in part by the California Sea Otter Voluntary Contribution Fund. More: CDFW mailbag: What's happening with butterflies, steelhead, birds, otters in oil spill areas The CDFW recently reviewed data from more than 500 sea otter necropsies and found that other causes of death include parasitic infections - mostly from land-based parasites - and poisoning by domoic acid. Unfortunately, most sea otters that are bitten die from their wounds. Sharks bite sea otters to determine if they are prey, but sometimes decide they’re not worth eating because they don’t have blubber like other marine mammals. In recent years, the leading cause of death for sea otters has been bites from white sharks. A: The CDFW has been monitoring sea otter mortality since 1968 to determine how to best care for injured or oiled sea otters and how to help recover California’s sea otter population.
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