UVM Theses and Dissertations
Format:
Print
Author:
Smith, Stephen J.
Dept./Program:
Wildlife and Fisheries Biology Program
Year:
2006
Degree:
M.S.
Abstract:
Sea lamprey (Petromyzon marinus) is a nuisance species in the Great Lakes and Lake Champlain that has inhibited recovery of salmonid populations. In an effort to optimize control efforts, recent research has focused on creating population models to evaluate various control scenarios. Accurate population parameters, such as fecundity and egg survival rates, are an important component of these models. The purpose of this research was to provide data on these information gaps in our understanding of lamprey life history in Lake Champlain.
After confirming that large proportions (90%) of sea lamprey eggs are washed from the nest, a suite of field and laboratory studies was used to investigate the fecundity of sea lamprey in Lake Champlain and factors affecting sea lamprey egg survival. Fecundity of sea lamprey was determined by sampling twenty-nine female sea lamprey. To determine the best morphometric indices to estimate fecundity, I examined the relationship between fecundity and length, weight, length and gonodosomatic index (GSI), weight and GSI, and several additional morphological measures. The mean estimated fecundity of our sample was 67,642 ± 6,578 (95% CI). Wet weight of the female is a more significant predictor of fecundity than total length. The addition of nine other morphometrics does not improve the fit of the model based on wet weight alone. Field trials were conducted to evaluate egg survival on different substrate types outside of the nest (spawning gravel and silt) using stream boxes. Boxes were constructed so that eggs could be introduced to stream substrates and later retrieved. Some boxes were covered to assess effects of excluding predation on eggs. Egg loss was significantly different between spawning gravel (65.6% ± 7.4%) and silt (93.4% ± 5.3%; p < 0.0001) and was not impacted by the presence of a cover on either substrate (p < 0.143). I used laboratory studies to examine predation on different substrates and incubation habitat as factors affecting sea lamprey egg survival. In predation studies crayfish, logperch, creek chub, and white sucker were allowed 18 hours to feed on sea lamprey eggs on five substrates: no substrate, silt, sand, spawning gravel, and cobble. Results show that substrate type has no effect on the numbers of eggs consumed by predators, but different predators do consume significantly different numbers of eggs (F-ratio = 11.12, df = 3, p <0.0001). Crayfish consumed 74% of available eggs, creek chub consumed 47.2%, white sucker consumed 8.7%, and logperch consumed 3.0% on average. I examined survival of sea lamprey eggs to stage 12 on three substrate types, silt, sand, and spawning gravel, using an experimental hatching system. Survival of eggs was significantly different among substrates (F-ratio = 27.74, df = 2, p< 0.0001). Egg survival on silt (69.2%) and sand (50.8%) was significantly higher than survival on spawning gravel (19.1%).
These results suggest that initial egg mortality is high because most spawned eggs are not deposited in the nest and predation on eggs not buried in a nest is likely high. Results also show that stream substrate alone does not affect hatching success, and that egg mortality may be highly variable depending on stream conditions. Under certain stream conditions, such as low flow, eggs outside of the nest may have relatively high survival. This information will help researchers to better understand and model sea lamprey populations, which will aid in the optimization of population control.
After confirming that large proportions (90%) of sea lamprey eggs are washed from the nest, a suite of field and laboratory studies was used to investigate the fecundity of sea lamprey in Lake Champlain and factors affecting sea lamprey egg survival. Fecundity of sea lamprey was determined by sampling twenty-nine female sea lamprey. To determine the best morphometric indices to estimate fecundity, I examined the relationship between fecundity and length, weight, length and gonodosomatic index (GSI), weight and GSI, and several additional morphological measures. The mean estimated fecundity of our sample was 67,642 ± 6,578 (95% CI). Wet weight of the female is a more significant predictor of fecundity than total length. The addition of nine other morphometrics does not improve the fit of the model based on wet weight alone. Field trials were conducted to evaluate egg survival on different substrate types outside of the nest (spawning gravel and silt) using stream boxes. Boxes were constructed so that eggs could be introduced to stream substrates and later retrieved. Some boxes were covered to assess effects of excluding predation on eggs. Egg loss was significantly different between spawning gravel (65.6% ± 7.4%) and silt (93.4% ± 5.3%; p < 0.0001) and was not impacted by the presence of a cover on either substrate (p < 0.143). I used laboratory studies to examine predation on different substrates and incubation habitat as factors affecting sea lamprey egg survival. In predation studies crayfish, logperch, creek chub, and white sucker were allowed 18 hours to feed on sea lamprey eggs on five substrates: no substrate, silt, sand, spawning gravel, and cobble. Results show that substrate type has no effect on the numbers of eggs consumed by predators, but different predators do consume significantly different numbers of eggs (F-ratio = 11.12, df = 3, p <0.0001). Crayfish consumed 74% of available eggs, creek chub consumed 47.2%, white sucker consumed 8.7%, and logperch consumed 3.0% on average. I examined survival of sea lamprey eggs to stage 12 on three substrate types, silt, sand, and spawning gravel, using an experimental hatching system. Survival of eggs was significantly different among substrates (F-ratio = 27.74, df = 2, p< 0.0001). Egg survival on silt (69.2%) and sand (50.8%) was significantly higher than survival on spawning gravel (19.1%).
These results suggest that initial egg mortality is high because most spawned eggs are not deposited in the nest and predation on eggs not buried in a nest is likely high. Results also show that stream substrate alone does not affect hatching success, and that egg mortality may be highly variable depending on stream conditions. Under certain stream conditions, such as low flow, eggs outside of the nest may have relatively high survival. This information will help researchers to better understand and model sea lamprey populations, which will aid in the optimization of population control.