<p>Pelagic fish distribution and diel behaviour patterns were studied in coastal areas in the north-western Baltic Sea Proper to understand more about how fish distribution and behaviour might affect planning and analyses of results of hydroacoustic surveys (Papers I and II). The vertical distribution of fish at night from spring to autumn showed seasonal and annual trends that could be explained by predictable and consistent seasonal changes, e.g., in temperature and stratification. Horizontal fish distributions did not show any trends probably owing to a lack of such seasonal characteristics. The observed vertical fish distribution over the diel cycle showed that hydroacoustic surveys at night were to be preferred over daytime surveys. At night, fish did not school and were generally less aggregated resulting in less variable hydroacoustic backscattering values and a higher percentage of single echo detections. By starting the surveys one hour after sunset and stopping one hour before sunrise, confusion between day- and nighttime behaviour in fish could be avoided. At night, fish occupied mid-water layers to a higher extent than surface and bottom layers, which was beneficial for the quality of the hydroacoustic data, particularly with respect to the hydroacoustic blind and dead zones (i.e. surface and bottom, respectively).</p><p>To quantify seasonal changes in pelagic fish abundance, densities and size distributions, nighttime hydroacoustic surveys were done every second week from spring through autumn in 2000 and 2001 (Paper III). There was a drastic increase in fish abundance and densities that started in early July and peaked in mid-August in both years. Analyses of the hydroacoustic data in relation to gillnet and trawl catches showed that the increase was caused mainly by young-of-the-year (YOY) herring. This age class is commonly not well represented in catches using traditional sampling methods like gillnets and trawling. Consequently, hydroacoustic data that have high precision and accuracy may improve quantitative estimates and our understanding of the biology in coastal nursery areas.</p><p>Baltic herring spawn in coastal areas and the density of metamorphosed YOY individuals may provide an early estimate of year-class strength. By analysing the relationship between parameters known to affect recruitment success and year-class strength in age 2 herring (YCS) a model that predicted herring recruitment was developed (Paper IV). The model explained 93 % of the variation in the number of age 2 herring over the period 1985-2000 and included the parameters YOY densities, climate (North Atlantic Oscillation index) and spawning stock biomass (SSB). Thus YCS could be predicted two years earlier than today and three years before entering the fishery. Up to the present, three new years (2001-2003) have become available for testing the model. For one of these years the predicted YCS was notably different from the assessed YCS. The reason for this is not fully understood, but for all three years SSB was outside the range used in the original model. Including the three new years into the data series resulted in a poorer explanation of the observed recruitment variation (55 %). A comparison of the standardized regression coefficients of both models showed increased significance for the parameter YOY (from 0.47 to 0.61).</p>

Pelagic fish distribution and diel behaviour patterns were studied in coastal areas in the north-western Baltic Sea Proper to understand more about how fish distribution and behaviour might affect planning and analyses of results of hydroacoustic surveys (Papers I and II). The vertical distribution of fish at night from spring to autumn showed seasonal and annual trends that could be explained by predictable and consistent seasonal changes, e.g., in temperature and stratification. Horizontal fish distributions did not show any trends probably owing to a lack of such seasonal characteristics. The observed vertical fish distribution over the diel cycle showed that hydroacoustic surveys at night were to be preferred over daytime surveys. At night, fish did not school and were generally less aggregated resulting in less variable hydroacoustic backscattering values and a higher percentage of single echo detections. By starting the surveys one hour after sunset and stopping one hour before sunrise, confusion between day- and nighttime behaviour in fish could be avoided. At night, fish occupied mid-water layers to a higher extent than surface and bottom layers, which was beneficial for the quality of the hydroacoustic data, particularly with respect to the hydroacoustic blind and dead zones (i.e. surface and bottom, respectively). To quantify seasonal changes in pelagic fish abundance, densities and size distributions, nighttime hydroacoustic surveys were done every second week from spring through autumn in 2000 and 2001 (Paper III). There was a drastic increase in fish abundance and densities that started in early July and peaked in mid-August in both years. Analyses of the hydroacoustic data in relation to gillnet and trawl catches showed that the increase was caused mainly by young-of-the-year (YOY) herring. This age class is commonly not well represented in catches using traditional sampling methods like gillnets and trawling. Consequently, hydroacoustic data that have high precision and accuracy may improve quantitative estimates and our understanding of the biology in coastal nursery areas. Baltic herring spawn in coastal areas and the density of metamorphosed YOY individuals may provide an early estimate of year-class strength. By analysing the relationship between parameters known to affect recruitment success and year-class strength in age 2 herring (YCS) a model that predicted herring recruitment was developed (Paper IV). The model explained 93 % of the variation in the number of age 2 herring over the period 1985-2000 and included the parameters YOY densities, climate (North Atlantic Oscillation index) and spawning stock biomass (SSB). Thus YCS could be predicted two years earlier than today and three years before entering the fishery. Up to the present, three new years (2001-2003) have become available for testing the model. For one of these years the predicted YCS was notably different from the assessed YCS. The reason for this is not fully understood, but for all three years SSB was outside the range used in the original model. Including the three new years into the data series resulted in a poorer explanation of the observed recruitment variation (55 %). A comparison of the standardized regression coefficients of both models showed increased significance for the parameter YOY (from 0.47 to 0.61).

Studies were conducted during late winter and spring of 1970 to establish the extent of spawning of Pacific herring (Clupea harengus pallasi Valenciennes) in the Yaquina estuary, and to define the degree of egg mortality on certain substrates. Routine surveillance of the north shore of the estuary provided information on the length of the spawning season, the number of separate spawnings which occurred, the extent of spawning into brackish water, and the types of substrates utilized for spawn deposition. Random sampling of egg deposits at specific locations within the estuary, and at frequent intervals following deposition provided estimates of spawn mortality on two commonly used plant substrates, Fucus sp. and Zostera sp. These included estimates of the amount of eggs removed from the substrates prior to commencement of hatching, and estimates of the mortality among eggs which remained attached to the substrates. One series of samplings of a deposit of eggs on Fucus was designed to establish the extent of bird predation on the eggs. Results from the spawn survey indicated that at least five separate spawnings occurred during the season. Initial spawning took place on February 5 in the lower estuary (from the south jetty to a point three miles upriver from the mouth). Subsequent spawnings occurred in the third, fifth, sixth, and seventh weeks following this initial deposition, and appeared to take place exclusively in the middle and upper estuary (from three and one half miles to ten miles upriver from the mouth). Among the substrates observed with eggs Fucus appeared to be the most extensively utilized, while localized deposits were noted on Zostera, bare rocks and pilings. Spawning was predominantly located on substrates lying above mean lower low water. Analysis of the samples collected from four populations of eggs deposited on Fucus, and one population deposited on Zostera revealed that egg removal was extreme during the period of incubation. Recorded losses from initially sampled populations of eggs on Fucus ranged from 78% to 1OO% based on sample means. A 9l% loss was recorded for the one Zostera population sampled. A comparison of a protected with an unprotected segment of a sampled population on Fucus indicated that birds contributed at least 80% to the removal of eggs from the unprotected segment. The observed presence of birds on all of the sampling areas when eggs were present suggests that predators accounted for the extensive losses from these areas. Analysis of the ratios of dead eggs to the total number of eggs in samples collected from Fucus substrates provided estimates of natural mortality. Low rates of mortality (about 20%) were recorded for two populations sampled during a period in which the weather was cool and moist, while considerably higher rates (about 50%) were observed in samples from a population exposed to a dry and relatively warm climate. Dessication of eggs was therefore indicated as a significant cause of mortality of eggs remaining attached to substrates exposed to drying conditions in the atmosphere. In addition to these field studies, a study was conducted in the laboratory to define the effects, on the survival of herring eggs to hatching, of combinations of three environmental parameters: temperature, salinity, and exposure to air. Groups of artificially fertilized eggs were incubated in the 18 test environments provided by the different combinations of three temperatures, three salinities, and exposure and non-exposure to air. Survival of eggs to hatching remained high (from 60% to 86% of total eggs in each environment) except for eggs incubated in the highest temperature ( 11 °C.) and subjected to eight hour exposure periods. Average survival in these environments was 5.2% and 24.2% (for two replicates). These observations lend support to the findings from the field sampling studies that survival of herrings eggs can be tenuous when subjected to exposure to air. / Graduation date: 1972

Thesis (Ph. D.)--University of Delaware, 1996. / Includes bibliographical references (p. 107-119).

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2009. / Submitted in partial fulfillment of the requirements of the degree Master of Science in Natural Resources (Fisheries), College of Natural Resources. Includes bibliographical references (leaves 176-190).

Incorporating molecular genetic data into management decisions would provide fisheries managers with new tools to identify the magnitude of population structure, metapopulation dynamics, at risk populations, and possible genetic interactions between species, so that management strategies could be tailored to better support long-term viability of species and populations. Alewife (Alosa pseudoharengus) and Blueback Herring (Alosa aestivalis) are two closely related anadromous clupeid fishes native to the Atlantic coast of North America. Current management strategies for these two species, collectively known as river herring, take no account of stock structure or even the distinction between the two species. Using 12 neutral microsatellite loci, I examined at multiple spatial scales the patterns of population structure and genetic differentiation for river herring, with particular reference to comparisons of population structure in the U.S., where extensive stocking has occurred, and Canada, where there has been no stocking. Results suggested strong population structure within the Canadian portion of the range and weaker population structure in the U.S. portion. Highly significant genetic isolation by distance (IBD) for parts of the range unaffected by stocking provided evidence of natal homing and limited dispersal. The differing IBD results obtained in three Canadian regions may reflect differences in historical biogeographical factors and contemporary dispersal patterns among regions. Very weak differentiation and an absence of significant IBD for American stocked populations provided evidence that stocking has reduced genetic differentiation between populations in the U.S. portion of the range, except for two divergent stocked populations that appeared to have resisted homogenization. Evidence of recent population bottlenecks were identified in both U.S. and Canadian populations. The genetic structure of Blueback Herring populations appeared to be similar to that seen in Alewife. When sampled in the same river, Alewife and Blueback Herring were strongly differentiated, although hybrids of the two species were detected. Evidence of genetic impacts of stocking, regional variation in patterns of population structure and complex genetic interactions between the species suggest that current management strategies should be re-evaluated.

Thesis (M. Sc.), Memorial University of Newfoundland, 1998. / Restricted until June 1999. Bibliography: leaves 104-110.

Thesis (M.S.)--Western Washington University, 2010. / Includes bibliographical references (leaves 45-53). Also issued online.

Thesis (doctoral)--Lugduni Batavorum, 1829. / Includes bibliographical references.

Marine capture fisheries contribute over 50% of total world fish production and more than 70% of this production is utilized for processing. The Canadian commercial fishing industry is one of the world’s most valued industries but generates large quantities of solid waste and wastewater. The increasing growth of the fish processing industry, the need for reduction of pollutants and the need to increase returns on raw material has led fish processors to adopt new ways of utilizing the wastes. In particular, efforts have focused on converting the biological substance in solid fish processing waste to various valuable compounds including both nutritional and non-nutritional products. Sulfated glycosaminoglycans (sGAGs) are heteropolysaccharide molecules with potential therapeutic applications and anticoagulant properties. Anticoagulants are responsible for curing major death-causing diseases such as strokes and cardiovascular diseases. The aim of this study was to develop an economically feasible technique to extract sulfated glycosaminoglycans (sGAGs) from fish processing waste. Two different fish (mackerel and herring) were used to optimize the extraction of sGAG. The effects of hydrolysis time (3, 6, 12 and 24 hrs) and papain concentration (15 and 20u/ml) on the extraction of sGAGs from different fish parts (whole fish, flesh, head, gut, fins and tails, skin and bones) were evaluated. The highest concentration of sGAGs (206.7 mg/g) was obtained from the mackerel head sample at 6 hrs of hydrolysis time and 20 u/ml of enzyme concentration while the highest concentration of sGAGs (236.3 mg/g) was obtained from herring gut at 12 hrs of hydrolysis time and 20 u/ml of enzyme concentration. The concentration of sGAG obtained from other part of mackerel were flesh (23.96 mg/g), waste (163.23 mg/g), fins and tail (86.63 mg/g), gut (203.52 mg/g), skin (105.45 mg/g) and bones (97.2 mg/g). However, the concentration of sGAG obtained from other parts of herring were flesh (39.34 mg/g), waste (130.15 mg/g), head (162.76 mg/g), fins and tail (148.53 mg/g), skin (65.89 mg/g) and bones (75.57 mg/g). Comparing the overall concentration of sGAG in waste samples of the fish, the mackerel produced higher sGAG than the herring.