Lake City Fisheries Research Office

Oak Grove, MN, United States

Lake City Fisheries Research Office

Oak Grove, MN, United States
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Dieterman D.J.,Lake City Fisheries Research Office | Frank J.,Hinckley Area Fisheries Office | Painovich N.,Hinckley Area Fisheries Office | Staples D.F.,Fisheries Biometrics Unit
North American Journal of Fisheries Management | Year: 2010

We assessed population status and estimated selected demographic parameters for lake sturgeon Acipenser fulvescens in the Kettle River, Minnesota, using capture-recapture tagging data collected from 1992 to 2007. The lake sturgeon is an imperiled species of special concern in Minnesota, with population declines attributed to overfishing, pollution, and establishment of dams. In 1995, the recreational fishery was closed and the only dam on the Kettle River (Sandstone Dam) was removed, in part to promote lake sturgeon recovery. Recent incidental capture of lake sturgeon by anglers is prompting interest in re-opening the recreational fishery. We gathered information to determine (1) status and demography of the Kettle River population, (2) the effect of dam removal, and (3) the feasibility of re-opening the recreational fishery. Openpopulation capture-recapture models were used to examine population status and estimate survival, seniority, and the relative importance of survival and recruitment for influencing population trends. The rate of population change (λ) indicated that the population was barely maintaining itself (average λ across years = 1.02; 95% confidence interval [CI]=0.86-1.16). Annual population estimates ranged from about 130 fish to almost 300 fish but had wide CIs. Similarly, estimates of new lake sturgeon entering the population each year (either from within-population recruitment or immigration) were variable and ranged from 0 to over 100. Annual survival was nearly constant at about 80%. Growth was slow relative to other populations but averaged about 28 mm/year for ages 6-21. A seniority parameter indicated that 49-87% of individuals in the population in a given year consisted of population members that survived from the previous year. This suggested that the population was essentially maintaining itself through a combination of episodic recruitment and relatively constant survival. Recent low recruitment may be due to a short-term disturbance from sediment released when the dam was removed in 1995. Maintaining closure of the recreational fishery still appears necessary. Bolstering of recruitment may be needed to increase the population. Full recovery will require patience for this long-lived, late-maturing, infrequently reproducing species. © American Fisheries Society 2010.

Dieterman D.J.,Lake City Fisheries Research Office | Walker T.S.,University of Minnesota | Cochran P.A.,University of Minnesota | Konsti M.,Section of Fisheries
North American Journal of Fisheries Management | Year: 2016

Brown Trout Salmo trutta are widely distributed fish that display substantial interpopulation variation in fundamental reproductive traits due to differences in local environmental conditions. This wide variation necessitates regional determination of key traits to aid local management efforts. In addition, several populations demonstrate a trade-off between fecundity and egg size, often as a function of growth history in response to environmental conditions. To determine these traits in the Driftless Area of the Upper Midwest, we identified two streams with contrasting environmental conditions and quantified reproductive traits just prior to the fall-spawning period in 2012. Reproductive traits included growth, length- and age-at-maturity, gonadosomatic index, and female fecundity and egg size. Environmental conditions were considered harsher at one site based on warmer water temperatures, more sand substrate, less adult fish cover, and presence of more potential interspecific competitors than at the other site. At both sites, Brown Trout of both sexes were short-lived; few Brown Trout older than age 3 were collected, and both sexes matured at age 2. Length-at-maturity ranged from 226 to 230 mm TL for males and from 214 to 238 mm TL for females. Fecundity and egg size were both positively related to female size, and females produced up to about 800 eggs. Ovaries represented a maximum of about 15% of female body weight. Female Brown Trout growth differed between the two sites, but most reproductive traits and growth of males did not. There was no evidence of a trade-off between fecundity and egg size, but length-adjusted egg sizes were significantly larger at the site with harsher environmental conditions. Differences in egg size probably were not due to the presence of competitors but may have been due to warmer water temperatures. Collectively, these fundamental reproductive data will prove useful for future population modeling efforts to support evaluation of several management strategies. © American Fisheries Society 2016.

Dieterman D.J.,Lake City Fisheries Research Office | Hoxmeier R.J.H.,Lake City Fisheries Research Office
Transactions of the American Fisheries Society | Year: 2011

We assessed recruitment, survival, emigration, and immigration of brown trout Salmo trutta in six interconnected stream reaches to quantitatively estimate how much immigrants contributed to population size in reaches in south eastern Minnesota. We also examined the influence of reach and season on estimates of survival and emigration via mark and recapture of individual trout representing three groups (age-0 juveniles, age-1 and age-2 adults, and age-3 + large adults). Immigration was calculated as 1 minus emigration. Recruitment varied among the six reaches and 3 years of this study (range, 0-1,292 fish/km). Survival of the age-0 group and that comprising ages 1 and 2 varied by season but not reach. Survival was highest in winter for both groups but lowest in spring for age-0 trout and in fall for age-1 and age -2 trout. Emigration varied by season for age-0 trout but by reach for trout of ages 1 and 2. For age-3 + trout, survival and emigration only varied by reach. Survival was highest and emigration was lowest in reaches with the most cover, including deep pools. From these demographic characteristics we estimated the proportions of the population that consisted of brown trout that had survived within a reach, recruited into it, or immigrated into it from some other reach. Immigration was predicted to contribute the most for the youngest age-group (35% or more of the predicted abundance of age-0 trout in most reaches) and is probably important for genetic purposes or to bolster population units in adjacent reaches. Our results for adult brown trout suggest that within-reach recruitment and survival contribute a larger proportion of trout to population units in many reaches than do immigrants. This confirms the appropriateness of current management approaches and suggests that maintenance of the exceptional recreational brown trout fishery in southeastern Minnesota is at least solidly dependent on factors promoting recruitment and survival within most managed stream reaches.

Dieterman D.J.,Lake City Fisheries Research Office | Hoxmeier R.J.H.,Lake City Fisheries Research Office | Staples D.F.,Fisheries Biometrics Unit
Ecology of Freshwater Fish | Year: 2012

Growth rate variation of three age groups of brown trout, Salmo trutta L. (age-0, 1 and 2, and 3+), was quantified from recaptured, individually tagged brown trout and related to season, stream reach, relative abundance, initial length and movement to examine factors influencing growth in length in three streams in the Midwestern United States. Total variation in growth was almost five times greater for age-0 than for age-3+ trout. Individual trout accounted for about 13% of total variation in age-0 growth, season about 57%, and trout initial length and relative abundance combined another 2%. The 2006 age-0 cohort had the fastest growth rates in their second spring and summer (2007) and slowest growth in their first winter (2006-2007). About 53% of total growth variation of age-1 and age-2 trout was accounted for by individual trout, season, initial length and stream reach. Predicted growth rates indicated strong effects of season and initial length. A significant interaction between these two factors indicated that, although smaller trout grew faster than larger trout, this length effect was most pronounced in spring and summer. About 35% of total growth variation of age-3+ trout was accounted for by individual trout and season. Together, season and individual trout characteristics were identified as the most important factors influencing brown trout growth in these streams. © 2012.

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