Geology topics

L.J. Begnoche

Publications and source records attributed to L.J. Begnoche.

3 recordsLinked to original sources

USGS2012

Exploring mechanisms underlying sex-specific differences in mortality of Lake Michigan bloaters

Sex-specific differences in mortality rates have been observed among freshwater and marine fish taxa, and underlying mechanisms can include sex-specific differences in (1) age at maturity, (2) growth rate, or (3) activity or behavior during the spawning period. We used a long-term (1973–2009) Lake Michigan data set to evaluate whether there were sex-specific differences in catch per unit effort, mortality, age at maturity, and length at age in bloaters Coregonus hoyi . Because bloater population biomass varied 200-fold during the years analyzed, we divided the data into three periods: (1) 1973–1982 (low biomass), (2) 1983–1997 (high biomass), and (3) 1998–2009 (low biomass). Mortality was higher for males than for females in periods 2 and 3; the average instantaneous total mortality rate ( Z ) over these two periods was 0.71 for males and 0.57 for females. Length at age was slightly greater (2–6%) for females than for males in different age-classes (3–6 years) during each period. Age at maturity was earlier for males than for females in periods 1 and 2, but the mean difference was only 0.2–0.4 years. To test the hypothesis that somatic lipids declined more in males than in females during spawning (perhaps due to increased activity or reduced feeding), we estimated sex-specific percent somatic lipids for fish sampled in 2005–2006 and 2007–2008. During 2005–2006, somatic lipids declined from prespawning to postspawning for males but were unchanged for females. During 2007–2008, however, somatic lipids were unchanged for males, whereas they increased for females. We found that sex-specific differences in Z occurred in the Lake Michigan bloater population, but our hypotheses that sex-specific differences in maturity and growth could explain this pattern were generally unsupported. Our hypothesis that somatic lipids in males declined during spawning at a faster rate than in females will require additional research to clarify its importance.

Transactions of the American Fisheries Society↗

USGS2009

Sexual difference in PCB concentrations of walleyes (Sander vitreus) from a pristine lake

We determined polychlorinated biphenyl (PCB) concentrations in 15 adult female walleyes (Sander vitreus) and 15 adult male walleyes from South Manistique Lake (Michigan, United States), a relatively pristine lake with no point source inputs of PCBs. By measuring PCB concentration in gonads and in somatic tissue of the South Manistique Lake fish, we also estimated the expected change in PCB concentration due to spawning for both sexes. To determine whether gross growth efficiency differed between the sexes, we applied bioenergetics modeling. Results showed that, on average, adult males were 34% higher in PCB concentration than adult females in South Manistique Lake. Results from the PCB determinations of the gonads and somatic tissues revealed that shedding of the gametes led to 1% and 5% increases in PCB concentration for males and females, respectively. Therefore, shedding of the gametes could not explain the higher PCB concentration in adult male walleyes. Bioenergetics modeling results indicated that the sexual difference in PCB concentrations of South Manistique Lake walleyes was attributable, at least in part, to a sexual difference in gross growth efficiency (GGE). Adult female GGE was estimated to be up to 17% greater than adult male GGE.

Science of the Total Environment↗

USGS2009

Thiamine content of eggs and lengths of coho salmon (Oncorhynchus kisutch) in relation to abundance of alewife (Alosa pseudoharengus) in eastern Lake ontario, 2003 to 2006

Early mortality syndrome in fry of Great Lakes salmonines is linked to reduced levels of thiamine in eggs, which reflects maternal consumption of forage fishes such as alewife (Alosa pseudoharengus) that contain thiaminase, an enzyme that destroys thiamine. We assessed annual variations in abundance and condition of alewives and thiamine status of coho salmon (Oncorhynchus kisutch) in Lake Ontario. We analyzed total thiamine in eggs of 20 coho salmon collected annually between 2003 and 2006 at the Salmon River Hatchery on the Salmon River, New York. Alewife abundance was assessed annually in southern and eastern Lake Ontario with bottom trawls during late April and early May. Mean thiamine concentration in eggs varied annually, with those collected in 2003 (2.5 nmol/g) being significantly higher than those collected in 2004 to 2006 (1.5 to 1.7 nmol/g). Although we did not test survival of fry, if reported threshold levels of thiamine for preventing mortality of Lake Michigan coho salmon fry apply, then many or most Lake Ontario coho salmon produced fry were likely to incur thiamine-deficiency mortality, especially during years 2004 to 2006. Comparison to indices of annual abundance of alewife in Lake Ontario with thiamine concentration in coho salmon eggs failed to show any significant correlations (P > 0.05). However, total length of female spawning coho salmon was positively correlated (P < 0.05) with increasing condition and estimated energy content of adult alewives in the previous spring. These results suggest that growth of coho salmon in Lake Ontario was first limited by energy intake, whereas the amount of thiamine provided by alewives was sufficient for growth (in length) but not for producing thiamine-adequate eggs.

East Lake Ontario↗