Sturgeon Life History and by Tom Cannon
This is a 3-part series by Tom Cannon on Sturgeon Populations, Science and Facts. Email thomascannon0@gmail.com for questions. Click Here to download full article.
White Sturgeon Life History: “White Sturgeon are anadromous fish that spend most of their lives within an estuary, usually returning to freshwater only to spawn. White Sturgeon have been found in some cases to travel hundreds of kilometers to other estuaries and river systems. When Sturgeon larvae hatch in a stream they begin swimming around in a vertical position as they are suspended by a yolk sac, making them more susceptible to be carried down to the estuary in the current. After they consume the sac they begin swimming freely and feeding through their mouth. In general the distribution of sturgeon in an estuary is age dependent and a function of salinity tolerance. The younger fish are found on the upstream or freshwater end of an estuary whereas the older fish are found on the ocean side. Once White Sturgeon have adapted to the changes in salinity they may move around a bay or estuary to find an optimal type of brackish water. They grow quickly in their first year, up to 30 cm FL in the San Francisco Bay estuary, and the growth rate generally decreases with age. The diet of young sturgeon consists primarily of different types of crustaceans, though they begin to increase the diversity with age. Most food is taken from the bottom of the estuary where the sturgeon may pick up clams, crabs, and shrimp. Larger sturgeon begin to feed on other fish such as anchovies, starry flounder, smelt and striped bass. The opportunism of the White Sturgeon can be seen in their documented consumption of crayfish, trout, frogs, salmon, crayfish and even one domestic cat. Male sturgeon reach sexual maturity before the females, though time of onset of maturity for both varies with photoperiod and temperature. Typically males are at least 10-12 years old and have a fork length of 75-105 cm. Females mature when they are 12-16 years old and have a fork length of 95-135 cm. White Sturgeon don’t necessarily breed annually and only a small percentage of the adult population spawn in a given season. Males may spawn every 1-2 years and females every 2-4 years. The sturgeon begin migrating in streams during winter, with large peak flows triggering the spawning between February and early June. The optimal water temperature for spawning falls in the range of 8-19°C. Fish biologists believe the White Sturgeon pick deep swift water areas to spawn such as riffles or pools with rock and gravel substrate. Female sturgeon produce many eggs, with the Sacramento White Sturgeon producing an average of 5,648 eggs per kilogram of body weight. Male sturgeon fertilize the eggs, giving them a tacky property that allows the eggs to stick to the substrate till the larvae emerge 4-12 days later. White Sturgeons have a long life span that may have exceeded 100 years historically.” Source
“White Sturgeon in California are believed to occur in primarily estuarine and riverine habitats, and spend only a small proportion of their time moving outside the estuary to the open coast. However, within the estuary, certain components of the estuarine fish and invertebrate communities are strongly affected by climate driven ocean variability (i.e., currents and temperature), whereas others more strongly responded to land-based climate processes, such as precipitation and outflow (Cloern et al. 2010; Peterson and Vayssieres 2010; Feyrer et al. 2015). Such mechanisms not only influence the estuarine environment, and thus the physiology of White Sturgeon, but also the abundance and distribution of organisms forming the food base for White Sturgeon.” (Kimmerer 2002; Peterson and Vayssieres 2010).
“White Sturgeon distribution is highly related to salinity patterns, with many fish inhabiting the brackish water of Suisun and San Pablo bays throughout the year (Kohlhorst et al. 1991). Further, these fish tend to move downstream in the winter when river flows tend to freshen Suisun Bay, and a portion move upstream into the Delta and lower Sacramento River beginning in fall and increasingly in winter, before presumably mature fish move farther into the Sacramento River in spring to spawn (Kohlhorst et al. 1991). In addition, abundance in the San Francisco Estuary is highly variable through time, and strong year-classes occur only in years when the Sacramento Valley Water Year index was rated “wet” and river flows were very high (Figure 1-3) (CDFG 2008). Changing ocean conditions will influence weather, precipitation and riverine flow and will likely affect sturgeon recruitment, particularly if years of high river runoff occur less frequently (Kohlhorst et al. 1991; Fish 2010). The frequency of wet years has declined across the decades from the 1980s through the present, leading to longer periods of little or no recruitment. This may have contributed to the declining adult abundances observed since that time.” Source
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Tom Cannon is an estuarine fisheries ecologist and biostatistician and has been involved in Delta fishery issues for more than 35 years. Over that period, Tom has worked for or been a consultant to the California Department of Fish and Wildlife, U.S. Bureau of Reclamation, National Marine Fisheries Service, State Water Contractors, CalFed Bay-Delta Program, State Water Resources Control Board, PG&E, California Striped Bass Association, Fisheries Foundation and CSPA. He has been involved in numerous habitat restoration projects. Find his reports on https://calsport.org/fisheriesblog/
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