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Current location: Home > Biological Effects Model > Adverse Effects > Reduced Fecundity/Fertility |
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Adverse Effect: Reduced Fecundity/Fertility Jump down this page to: Steelhead | Chinook Salmon | Delta Smelt | Longfin Smelt | Sacramento Splittail | White Sturgeon | Green Sturgeon | Striped Bass All fishes have an incipient limiting threshold for DO below which they experience a decline in the ability to perform certain activities and functions. Little information is available on the effects of low DO concentrations on fecundity and fertility. Brungs (1971) reported spawning failure and reduced fecundity in fathead minnows exposed to DO concentrations of 1–2 mg/L, although the mechanisms for these effects were not investigated. Jump to "General Effects" discussion under other adverse effects: Steelhead (Oncorhynchus mykiss) Hypothesis: Exposure of adult steelhead to low DO concentrations adversely affects fecundity. 1. What is the mechanism causing this adverse effect? Low DO concentrations can reduce fecundity by limiting metabolic rates and the availability of metabolic energy for gamete production or increasing the amount of energy needed to reach the spawning grounds (thus decreasing energy reserves for gamete production). 2. Are there critical thresholds associated with this adverse effect? Critical thresholds associated with the adverse effect of low DO concentrations on fecundity have not been identified. 3. How important is this mechanism? The potential adverse effects on significant numbers of adult steelhead is low because most adults migrate through the Delta in the late fall to early spring when DO concentrations frequently exceed the regulatory minimum. 4. How well is this mechanism understood? No empirical or experimental evidence of the effect of low DO concentrations on fecundity is available. The potential for such an effect is based on general knowledge of fish bioenergetics. Jump to "Steelhead" discussion under other adverse effects: Chinook Salmon (Oncorhynchus tshawytscha) Hypothesis: Low concentrations of DO result in reduced fecundity/fertility. 1. What is the mechanism causing this adverse effect? Low DO concentrations can reduce fecundity by limiting the amount of metabolic energy available for gamete production through direct effects (reducing the amount of available oxygen for gamete production) or indirect effects (delaying or disrupting migration and increasing energy expenditures during migration). 2. Are there critical thresholds associated with this adverse effect? Critical thresholds associated with adverse effects of low DO concentrations on Chinook salmon fecundity have not been established. 3. How important is this mechanism? This mechanism may be important because of the potential for overlap in the timing of upstream migration of adult Chinook salmon and the occurrence of low DO concentrations in the DWSC. 4. How well is this mechanism understood? Suitable water temperatures have been reported for adult migration and holding (see Exposure to High Water Temperatures), but critical temperature and DO thresholds for egg viability and fecundity have not been identified. Jump to "Chinook Salmon" discussion under other adverse effects: Delta Smelt (Hypomesus transpacificus) Hypothesis: Delta smelt exposed to DO concentrations below the regulatory minimum have reduced fecundity/fertility. 1. What is the mechanism causing this adverse effect? Some fish species experience reduced gamete formation as a result of chronic exposure to low DO concentrations (General Effects), but no studies on the effect of low DO concentrations on delta smelt fecundity/fertility have been published. 2. Are there critical thresholds associated with this adverse effect? The incipient limiting threshold for delta smelt has not been determined. 3. How important is this mechanism? Reductions in gamete production in delta smelt as a result of exposure to low DO concentrations in the DWSC are not likely to be an important limit on this species’ population. Reductions in gamete production are likely not important because:
4. How well is this mechanism understood? This mechanism is not well understood because no studies of the effect of low DO concentrations on gonad development and gamete production have been published. Jump to "Delta Smelt" discussion under other adverse effects: Longfin Smelt (Spirinchus thaleichthys) Hypothesis: Longfin smelt exposed to DO concentrations below the regulatory minimum do not have reduced fecundity/fertility. 1. What is the mechanism causing this adverse effect? Some fish species experience reduced gamete production as a result of chronic exposure to low DO (General Effects), but no studies on the effect of low DO on longfin smelt fecundity/fertility have been published. 2. Are there critical thresholds associated with this adverse effect? Like other fishes, longfin smelt have an incipient limiting threshold for DO below which they experience a decline in the ability to perform certain activities and functions. The incipient limiting threshold for longfin smelt has not been determined. 3. How important is this mechanism? Reductions in gamete production in longfin smelt as a result of exposure to low DO concentrations in the DWSC are not likely to be an important limit on this species’ population. Longfin smelt are not detected frequently in the DWSC, most or all of the species’ current spawning territory is located north and west of the DWSC, and longfin smelt that did spawn in or near the DWSC would be at the end of their upstream migration so gametes would probably be completely developed by the time they arrived at the reach of the DWSC that is affected by low DO concentrations. Longfin smelt exposure to low DO concentrations in the DWSC would probably too brief to result in substantial changes in gamete production. 4. How well is this mechanism understood? No studies of the effect of low DO concentrations on gonad development and gamete production in longfin smelt have been published. Jump to "Longfin Smelt" discussion under other adverse effects: Sacramento Splittail (Pogonichthys macrolepidotus) Hypothesis: Sacramento splittail exposed to DO concentrations near the regulatory minimum do not experience reduced fertility. 1. What is the mechanism causing this adverse effect? Some fish species experience reduced gamete production as a result of chronic exposure to low DO concentrations (General Effects), but no studies on the effect of low DO concentrations on Sacramento splittail fecundity/fertility have been published. 2. Are there critical thresholds associated with this adverse effect? The incipient limiting threshold for Sacramento splittail has not been determined; however, given that their incipient lethal threshold is very low, it is likely that their incipient limiting threshold is well below the regulatory minimum. 3. How important is this mechanism? The impact on Sacramento splittail fertility of low DO concentrations in the DWSC is unknown. 4. How well is this mechanism understood? No studies of the effect of DO concentrations on gonad development and gamete production have been published. Jump to "Sacramento Splittail" discussion under other adverse effects: White Sturgeon (Acipenser transmontanus) Hypothesis: White sturgeon exposed to DO concentrations below the regulatory minimum have reduced fecundity/fertility. 1. What is the mechanism causing this adverse effect? Some fish species experience reduced gamete production as a result of chronic exposure to low DO concentrations (General Effects), but no studies on the effect of low DO concentrations on white sturgeon fecundity/fertility have been published. Given that white sturgeon exposed to mild hypoxia (58% saturation—4.7–5.7 mg/L) experience a significant reduction in metabolism and oxygen consumption, it is likely that exposure to low DO concentrations of intermediate duration (days) during gamete development would reduce overall fecundity/fertility as gametogenesis is a metabolically intensive activity. 2. Are there critical thresholds associated with this adverse effect? Like all other fishes, white sturgeon have an incipient limiting threshold for DO below which they experience a decline in the ability to perform certain activities and functions. The incipient limiting threshold for white sturgeon has not been determined. 3. How important is this mechanism? Reductions in gamete production in white sturgeon as a result of exposure to low DO concentrations in the DWSC might limit this species’ population growth rate. Much of the species’ spawning territory is located north of the DWSC. However, individual gravid female sturgeon may carry a measurable portion of the eggs that will be laid in any give year. Females are very fecund (individual females may carry, on average, 200,000 eggs) (Moyle 2002), and only a small portion of females spawns in a given year. Thus, even a small percentage reduction in the fecundity of individuals may cause a measurable reduction in the production of sturgeon eggs for that year. 4. How well is this mechanism understood? No studies of the effect of DO on gonad development and gamete production have been published. Jump to "White Sturgeon" discussion under other adverse effects: Green Sturgeon (Acipenser medirostris) Although little species-specific information is available for green sturgeon, it is likely that information for white sturgeon is generally applicable to green sturgeon. Jump to "Green Sturgeon" discussion under other adverse effects: Striped Bass (Morone saxatilis) Hypothesis: Striped bass exposed to DO concentrations below the regulatory minimum have reduced fecundity/fertility. 1. What is the mechanism causing this adverse effect? Low DO concentrations can directly affect fecundity by limiting the amount of metabolic energy available for gamete production or constricting the amount of suitable habitat with adequate DO concentrations. Avoidance of habitats with low DO concentrations may result in poor body condition and reduced fecundity as a result of overcrowding of available suitable habitats and reduced food supply (Coutant 1985, 1990). 2. Are there critical thresholds associated with this adverse effect? Prolonged exposure to sublethal DO concentrations (2–3 mg/L) may reduce fecundity (see above) (Coutant 1985, 1990). Talbot (1966 in Coutant 1985) indicated that DO concentrations of 4 mg/L were too low to support successful spawning and reproduction. 3. How important is this mechanism? Reductions in gamete production in striped bass as a result of exposure to low DO concentrations in the DWSC are not likely to be an important limitation on this species’ population because much of the spawning in the lower San Joaquin River occurs downstream of the DWSC and because the duration of adult striped bass exposure to low DO concentrations in the DWSC is probably too brief to result in major changes in gamete production. 4. How well is this mechanism understood? The effect of low DO concentrations in the DWSC on the fecundity of striped bass is unknown. Jump to "Striped Bass" discussion under other adverse effects: |