The growth of largemouth bass, Micropterus salmoides (Lacepede), under constant and fluctuating temperatures

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73493/1/j.1095-8649.1984.tb04787.x.pd

Simulation of Mechanisms Causing Stunting in Northern Pike Populations

Some mechanisms hypothesized to cause stunting of northern pike Esox lucius include overpopulation and competition, lack of appropriately sized prey, and lack of thermal refuges in midsummer. The objective of this work was to use an energetics model of northern pike growth over 3 years to test the effects of these mechanisms on stunting. Simulations for females indicated the following: (1) competition‐based stunting could occur when food resources were reduced by only 5–10% per individual, such that size at age 3 would be reduced by up to 51%; (2) lack of appropriately sized prey could result in stunting (up to 35% of a northern pikeˈs annual ration often comes from large and rare prey), such that size at age 3 could be reduced 80%; (3) inappropriate thermal regimes could reduce northern pike growth up to 58%, but only under extremely warm conditions.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141197/1/tafs0612.pd

Energy Storage, Growth, and Maturation of Yellow Perch from Different Locations in Saginaw Bay, Michigan

The growth and abundance of yellow perch Perca flavescens in Saginaw Bay have varied historically. Changes in growth have been ascribed to many causes, including density and genetic composition of the fish stock, both of which are also believed to vary with location in the bay. The objectives of this study were to compare growth and maturation of yellow perch from inner and outer Saginaw Bay, to investigate the existence of different fish stocks, and to compare growth of yellow perch in Saginaw Bay to growth in other locations to determine the degree of stunting. Yellow perch were collected from four sites in inner and outer Saginaw Bay from 1983 to 1985. Size distributions differed between the inner and outer bay sites: larger and older fish were more common in the outer bay. Percentage of body water, body energy density, gonadosomatic index, and age at maturation did not differ between the inner and outer bay sites. Growth in weight, total body energy, and condition factors differed significantly. These results indicate that growth conditions differ between the inner and outer bay, but the fish populations may not be isolated completely, as has been suggested. Results also suggest that the growth differential has not caused large geographic differences in growth rate, but has caused small condition differences. Yellow perch growth is poor in Saginaw Bay, and the fish appear unable to store substantial energy reserves at any time of year. It appears that behavioral differences between young and old fish may cause the differential distribution of fish by size in Saginaw Bay.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142193/1/tafs0976.pd

Field Test of Two Energetic Models for Yellow Perch

Field data from a population of yellow perch Perca flavescens in Saginaw Bay, Lake Huron, were used to evaluate the ability of two energetic models to predict consumption by yellow perch. Field estimates of daily ration for age‐1–4 fish during May through October 1987 and 1988 were compared with independent predictions made by the Wisconsin energetic model and an energetic model developed by Karås and Thoresson. Predictions of daily ration using the Wisconsin model were lower than daily rations estimated from field data for all ages, primarily due to poor model–field agreement at temperatures above 22°C. This caused estimates of cumulative consumption from the Wisconsin model to be 25–50% lower than field estimates. Predictions of daily ration by the Karås–Thoresson model agreed with field estimates over a temperature range of 10–26°C for age‐1–3 yellow perch but not for older fish. Despite improvement, model predictions of cumulative consumption were 2–35% lower than field estimates. Although these tests of predicted and estimated rations may provide insight into which model produced more accurate results, it must be emphasized that field measures of daily ration are also estimates and may be in error, particularly at temperatures above 22°C where gastric evacuation rates were estimated. The Karås–Thoresson modification of the Wisconsin energetic model produced better fits to field ration data and is recommended for model applications.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142095/1/tafs0414.pd

Role of life cycle assessment in sustainable aquaculture

As an alternative food source to wild fisheries, aquaculture shows a great potential to help meet the growing demand for seafood and animal protein. The expansion of aquaculture has been achieved partly by system intensification, which has drawn vast criticisms of aquaculture for its environmental, social and economic sustainability issues. Life cycle assessment (LCA) has become the leading tool for identifying key environmental impacts of seafood production systems. A LCA evaluates the sustainability of diverse aquaculture systems quantitatively from a cradle‐to‐grave perspective. It provides a scientific basis for analysing system improvement and the development of certification and eco‐labelling criteria. Current efforts focus on integrating local ecological and socio‐economic impacts into the LCA framework. A LCA can play an important role in informing decision makers in order to achieve more sustainable seafood production and consumption. This article reviews recent applications of LCA in aquaculture, compares the environmental performance of different aquaculture production systems, explores the potential of including biodiversity issues into LCA analysis and examines the potential of LCA in setting criteria for certification and eco‐labelling.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98772/1/raq1080.pd

Timing of Supplemental Feeding for Tilapia Production

The staged addition of feed to fertilized fish ponds was evaluated by adding fertilizers to 15 ponds stocked with Nile tilapia Oreochromis niloticus , then adding feed at half ad libitum rates once fish in the ponds reached a target weight. Each pond was stocked with 750 fish (3 fish/m 2 ), and each treatment included three ponds with first feeding at (a) 50 g, (b) 100 g, (c) 150 g, (d) 200 g, and (e) 250 g. Ponds in Thailand (at the Ayutthaya Freshwater Fisheries Station, Royal Thai Department of Fisheries) were maintained for 236–328 d until the fish reached 500 g. Growth was similar for all treatments under fertilizer alone (1.17 g/d) and was also similar when feed was applied (3.1 g/d). Feed application rates averaged 1.17% BW/d, indicating substantial use of natural food. Pond water quality did not deteriorate under supplemental feeding. Feed conversion rates averaged 1.03. Multiple regression indicated that 73.8% of the variance in growth was explained by design variables (feed input and days), while 86.2% of the variance in growth was explained by adding dissolved oxygen content and alkalinity into the equation. The most efficient system was to grow fish to 100–150 g with fertilizers alone, then add feed. First adding feed (at 50% ad libitum) once fish reached 100 g produced the highest predicted annual revenues ($6,164 per hectare). Results of this experiment indicated that either critical standing crop occurred early (before the first fish sample) or did not occur at all in these ponds.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73113/1/j.1749-7345.1996.tb00625.x.pd

Movement Patterns of Large Brown Trout in the Mainstream Au Sable River, Michigan

We used radiotelemetry to monitor spring and summer movements of 11 brown trout Salmo trutta (442–584 mm) for up to 904 d in a Michigan stream. Individual brown trout used a few specific locations near cover (referred to as home sites) as resting locations during the day, moved across various distances at night, and generally returned to the same home site the next morning. Home sites were predominantly artificial cover (88%) rather than natural sites, as natural cover was very limited in the study area. Some fish used multiple home sites, and the average separation between multiple home sites for individual fish was over 500 m. Fish tracked for more than 1 year used the same home sites each summer and generally exhibited similar behavior each year. Fish belonged to two general categories of daily movement behavior: mobile or stationary. Mobile fish tended to move frequently and were found within their home sites only 43% of the time at night. Stationary fish did not move far from home sites, even at night. There was a negative correlation between the average gradient and the maximum distance fish moved from their home sites during nocturnal periods. Stationary fish resided in areas of steeper gradient (usually about 0.20%) and moved less often nocturnally than did mobile fish. Three fish were tracked extensively over 36 d to quantify diel activity patterns. The hourly activity of fish increased dramatically at dusk, continued at a lower level overnight, and then increased again at dawn before declining to near zero during the day. This behavior pattern was similar among all individuals tracked and also between the months of June, July, and August for an individual fish. Nocturnal movements involved significantly greater distances than diurnal movements for these fish. The relationship between movement and gradient may indicate energetic tradeoffs between the cost of moving against a current and the energy gained during active foraging. Also, the dominant use of artificial home sites has implications for the value of habitat improvements meant to increase abundance of large brown trout.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141462/1/tafs0034.pd

Lake Characteristics Influencing Spawning Success of Muskellunge in Northern Wisconsin Lakes

We determined the physical, chemical, biological, and land use characteristics that distinguish northern Wisconsin lakes with self‐sustaining populations of muskellunge Esox masquinongy from lakes where stocking is required to maintain populations. Lakes that supported self‐sustaining muskellunge populations were characterized by fewer shoreline alterations and by spawning habitats with softer, organic‐nitrogen‐rich sediments. Lakes that required stocking had extensively developed shorelines. The direction of water level change during the spawning period, percentage of spawning area sediment covered by woody debris, number of deadfall trees per kilometer of shoreline, and percentage of shoreline that was totally developed were the most important variables for classifying the level of muskellunge reproduction a lake could support. A linear discriminant function correctly classified 83% of the lakes with self‐sustaining muskellunge populations and 89% of the lakes requiring stocking to sustain or enhance muskellunge populations. Lake managers wishing to use muskellunge stocking programs to reestablish self‐sustaining populations should critically review each candidate lake by considering our model and that of Dombeck et al. (1986).Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141695/1/nafm0834.pd

Effects of age, sex, and anthropometric factors on nerve conduction measures

Associations among measures of median, ulnar, and sural nerve conduction and age, skin temperature, sex, and anthropometric factors were evaluated in a population of 105 healthy, asymptomatic adults without occupational exposure to highly repetitive or forceful hand exertions. Height was negatively associated with sensory amplitude in all nerves tested ( P < 0.001), and positively associated with median and ulnar sensory distal latencies ( P < 0.01) and sural latency ( P < 0.001). Index finger circumference was negatively associated with median and ulnar sensory amplitudes ( P < 0.05). Sex, in isolation from highly correlated anthropometric factors such as height, was not found to be a significant predictor of median or ulnar nerve conduction measures. Equations using age, height, and finger circumference for prediction of normal values are presented. Failure to adjust normal nerve conduction values for these factors decreases the diagnostic specificity and sensitivity of the described measures, and may result in misclassification of individuals. © 1992 John Wiley & Sons, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50152/1/880151007_ftp.pd