Aspects of the behaviour of adult Atlantic salmon in estuaries, while on their spawning migration has been investigated using a salinity telemetric system. Eighteen fish were tracked in total in different Scottish estuaries. Studies involving the displacement of salmon from freshwater back into higher salinities on the River North Esk, Montrose showed fast movement through the estuary back into freshwater (5h), movement being initiated by the sensing of low salinities or the start of the flood tide. Tracking in the Dornoch Firth at Bonar Bridge (a channel type estuary) showed fish maintaining one position against both flood and ebb tides, experiencing salinities fluctuating widely about the isosmotic point. The qualitative assessment of salmon on passage through the estuary of the freshwater discharge of a non-natal river was also demonstrated, repeated entries of a very brief nature (21s) being recorded. The position held by salmon whilst on suspended migration in an estuary was recorded, no sampling of the freshwater discharge being undertaken on a tidal basis. The resting metabolic rate of farmed salmon of different stages of sexual development was recorded in saltwater, and on transfer to freshwater. Maturing fish exhibited a raised metabolic rate in saltwater, suggesting increased osmoregulatory costs. This was in contrast to non-maturing fish. The cannulation of wild salmon subjected to fluctuating salinities was undertaken. Plasma electrolyte levels and osmolalities of fish subjected to cyclic salinities were intermediate between salt-adapted and freshwater-adapted values, showing only small fluctuations. An inability to osmoregulate successfully in high salinities following 'stress' events was recorded in maturing farmed and coastally caught wild salmon, suggesting a maladaption to that environment. By contrast, non-maturing farmed salmon exhibited a greater degree of euryhalinity. Examination by electron scanning microscopy of apical pit structure of gill chloride cells supports the idea that increasing maturity or freshwater exposure reduces tolerance to saltwater. It is concluded that Atlantic salmon are euryhaline during at least part of their oceanic feeding phase, and on arrival in coastal waters on the spawning migration require no period of acclimitisation to freshwater. A reduction in tolerance to high salinities linked to advancing maturation/ freshwater exposure would thus serve to ensure river entry.

The blue crab, Callinectes sapidus, supports a successful fishery in the Atlantic Ocean and throughout the Gulf of Mexico, with a total landing of 8,158,788 lb. and a total value of $10,562,128 for the state of Florida during 2012 (FWC 2012 Annual Landings Summary). An accurate and comprehensive understanding of the blue crab's life history and seasonal migration behavior is essential in defining effective management strategies for the fishery. Tag recapture studies and ultrasonic tracking methods for studying blue crab migrations are costly in terms of time and resources. In this study an alternative approach, microchemical natural tagging, was successfully used to determine a female's mating habitat. This approach assumes that the exoskeleton of the post-terminal molt female blue crab reflects the mating habitat's chemical signature and that the chemical signals are stable over time. To test these hypotheses, mature female blue crabs were collected from two Tampa Bay locations. Collected crabs were placed in tanks for 29 days, a subset was sacrificed at T = 0 and then twice per week, and the exoskeletons were analyzed via Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Elemental Analyzer Infrared Mass Spectrometry (EA-IRMS) to observe the stability of the exoskseletal chemical signature over time. Over the 29 day time series, no significant change in the concentrations of Li, Ca, and Ba, or the isotopic ratios of 13C/12C (δ13C) and 15N/14N (δ15N) were observed (ANOVA p-value > 0.05). A Canonical Analysis of Principal Coordinates (CAP)-based discriminate analysis with leave-one-out cross-validation collectively compared Li concentrations, δ13C, and δ15N among five Tampa Bay locations, producing a confusion matrix successfully classifying field collected crabs into: Alafia River 33%#37;, Little Manatee River 71%#37;, Palm River 67%#37;, Safety Harbor 30%#37;, and Skyway Fishing Pier 83%#37;, with an overall classification success of 66%#37;. These results suggest that the largest biomass component of the migratory pulse collected near the mouth of Tampa Bay was dominated by crabs originating from an area not widely harvested by commercial fishermen, as relatively few of the migrating females were matched to riverine locations that were intensively fished. Instead, most appeared to originate from open waters of Tampa Bay. It is possible that low densities of blue crab inhabiting a large area that is not commercially fished, effectively shields a proportion of the individuals in the Tampa Bay estuary from economic exploitation, creating a density-dependent natural harvest refugium.

<p>This dissertation investigated spawning biology of female blue crabs, <italic>Callinectes sapidus</italic>. Females mate following the terminal molt and undertake a spawning migration seaward, producing multiple clutches of larvae. To examine lifetime reproductive potential of female crabs, individual crabs were confined in the field from terminal molt to death. Crabs produced up to 7 clutches over 1-2 spawning seasons and survived up to 394 d after the terminal molt. Time to first clutch and time between clutches were positively correlated with carapace width and best described by degree-days. Size at maturity was negatively correlated with water temperature on the day of the terminal molt. Most measurements of clutch quality and larval fitness were similar for all clutches. The percentage of embryos developing normally decreased 40% from clutch 1 to clutch 4 and clutch volume decreased 50% from clutch 1 to clutch 5. Thus, most of a crab's reproductive output is from the first few clutches. </p><p>Using swimming and abdominal pumping assays, the roles of pheromones in larval release and migratory behavior were investigated. Following delivery of egg extract, bradykinin (a pheromone mimic), and trypsin (an enzyme that generates peptide pheromones), ovigerous crabs responded with increased abdominal pumping, indicating that peptide pheromones stimulate larval release in blue crabs. Ovigerous crabs responded with increased swimming following delivery of egg extract, but not following delivery of a peptide pheromone mimic or an enzyme that produces peptide pheromones. These results suggest that some substance generated from the egg mass stimulates vertical swimming, but that peptides alone do not stimulate swimming. A blend of molecules, possibly including sugars, may be the cue that stimulates swimming behavior. </p><p>Endogenous rhythms in vertical swimming, a mechanism underlying migration in tidal estuaries, were examined in the laboratory under constant conditions in juvenile females, recently-molted females, and females with mature ovaries from Beaufort, NC. Rhythms were variable in each stage, though circatidal rhythms consistent with ebb tide transport were observed in juvenile females and recently-molted females. Crabs with mature ovaries typically swam around the time of high tide. Rhythms were also examined for ovigerous females collected from estuaries with three different tidal regimes: semi-diurnal, diurnal, and non-tidal. Crabs from the tidal estuaries had circatidal or circalunidian swimming rhythms with period lengths corresponding to the tidal period of their home estuary. Swimming occurred primarily on ebb tide. Crabs from the non-tidal estuary had a circadian rhythm of vertical swimming around the time of sunset. Such a rhythm has no obvious migratory significance and migration likely takes place though another mechanism.</p><p>Swimming behavior was also examined in the field in one non-tidal site and three tidal sites. Crabs were tethered in the field and swimming was monitored using archival pressure tags. Crabs tethered in the non-tidal site did not swim, possibly due to the lack of necessary environmental cues. Crabs at the tidal sites swam primarily on ebb tides. Swimming was greatest at the deepest site, which also had the strongest currents. This site is known to be a migratory area for spawning blue crabs. Decreased swimming behavior was observed at the two shallower sites, including one site that is known to be habitat for all stages of blue crabs. These results indicate that swimming behavior is variable among different areas in a single estuary. In areas where swimming is reduced, crabs may continue migrating seaward by walking or may spend additional time in that area to forage. Within each site, peak swimming generally occurred during the time of the most rapid decrease in water level, suggesting that hydrostatic pressure may serve as a cue for swimming. </p><p>Mark-recapture studies were conducted in three rivers (North River, South River, Adams Creek) in eastern North Carolina, and recently-molted female crabs were tagged to ensure a relatively constant time since molting. Most crabs traveled relatively short distances and were recaptured before producing a clutch of eggs. Individuals that moved substantial distances typically moved down-estuary. The Adams Creek canal, connecting Adams Creek with the Newport River estuary, functioned as a migratory corridor, as crabs from both Adams Creek and South River migrated down the canal, presumably using ebb tide transport. Many of the crabs that migrated down the canal into the Newport River were recaptured while ovigerous. Results of this study support the hypothesis that rapid long-distance migratory movements do not begin until production of the first clutch of eggs, though some down-estuary movement takes place by prior to production of the first clutch of eggs.</p><p>Female blue crabs mate following the terminal molt and begin moving seaward soon thereafter by walking and swimming. Once the appropriate salinity (> 22 ppt) is reached, the first clutch of eggs is produced and migration rate rapidly increases. Blue crab spawning biology should be similar throughout the range of the species. After taking latitudinal temperature variation and other local variables into account, results presented here should be applicable not only to blue crabs in North Carolina, but in other areas as well.</p> / Dissertation

Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye.

Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye.

Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye. / Forestry, Faculty of / Graduate

Made available in DSpace on 2015-03-05T16:19:36Z (GMT). No. of bitstreams: 0 Previous issue date: 30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O conhecimento da estratégia de vida, estrutura populacional e comportamento são fundamentais para a compreensão da biologia dos peixes e imprescindíveis para a elaboração de planos de conservação. Prochilodus lineatus é uma espécie reofílica, migradora, com grande biomassa e considerada relevante economicamente. Com ampla distribuição nas bacias do Brasil, vem sofrendo uma redução na densidade populacional devido o impacto antrópico como diminuição das áreas de desova, rotas migratórias afetadas pôr barragens e construções de usinas e por pesca intensiva. Através da utilização da radiotelemetria foram investigadas as migrações, o habitat de estadia, a atividade diária e sazonal e estabelecimento do período reprodutivo. De Agosto de 2002 a Março de 2004, 19 grumatãs foram marcados com rádio-transmissores (149.640MHz, 320 dias de vida, LOTEK Canadá Ltda.) na cavidade peritoneal. Semanalmente os peixes foram rastreados, usando barco ou avião. O monitoramento através de estações fixas foi permanente. Cada estaçã / Life strategy, population structure and behavior are fundamental elements for the comprehension of fish biology and essential for conservation. The grumatã, (Prochilodus lineatus; Prochilodontidae) is a reophilic migratory species of economical importance for local fisheries. It is widely distributed in Brazil. During the last decades grumatã populations seem to have declined due to river damming by power plant constructions, pollution, habitat degradation and heavy fishing pressure. The present study investigated circadian and seasonal activity patterns, spawning migration and habitat use. Between August 2002 and March 2003 nineteen Grumatã were tagged internally with digitally coded radio transmitters (149 MHz). Mobile tracking was carried out weekly by boat or aircraft. Additionally six data loggers recorded movements of tagged fish. Results showed that the mean distance covered per fish and day was positively related with fish weight (r2 =0.3102; p=0.013). Grumatã showed a preference for river reaches su

I Österdalälven har mängden Siljansöring (Salmo trutta) minskat avsevärt på grund av kraftverk som stoppar fiskens vandringsvägar. För att lyckas med att stärka beståndet krävs en fördjupad kunskap kring fiskens beteendemönster, bland annat rörelser i samband med uppströms lekvandring. Denna studie är ett försök att ge en överblick av den lekmogna Siljansöringens uppströmsvandring i Österdalälven och se om det föreligger några skillnader mellan odlad/vild öring respektive hanar/honor. Genom akustisk telemetri har 18 Siljanöringars rörelser längs en begränsad älvsträcka registrerats under 56 dagar. Analys har gjorts för hitta variationer både rumsligt och tidsmässigt samt mellan odlade/vilda Siljansöringar respektive honor/hanar, likväl som skillnader avseende rörelser, tim- och dygnsaktivitet och benägenhet att söka sig uppströms till det definitiva vandringshindret Spjutmo kraftverk. Siljansöringarna rörde sig mer under dagen jämfört med natt vilket skulle kunna kopplas till påverkan från elproduktion och vattenströmmar som skapas vid Spjutmo kraftverks turbinutlopp och/eller att dagsljuset är en fördel då de använder sig av synintryck för att kunna navigera. Skillnader (dock ej statistiskt säkerställda) kunde urskiljas mellan odlade och vilda fiskar och hanar/honor, såsom exempelvis att vild fisk simmade längre sträckor än odlad. Studier som denna är viktiga för att kunna få en helhetsbild kring livsvillkor och beteendemönster för Siljansöring och därigenom lyckas med framtida förvaltnings- och åtgärdsarbeten. / The number of Siljan trout (Salmo trutta) in the River Österdalälven has declined due to hydropower development. To restore the river information about the behavioural patterns of the trout, such as upstream migration, are needed. The aim of this study is to describe the upstream movements of tagged Siljan trout as well as to identify differences between hatchery-reared and wild trout and between males and females. During 56 days, 18 individuals tagged with acoustic telemetry transmitters were registered in a section of the River Österdalälven. The data were analysed to identify variation in time and space as well as differences between origin (hatchery-reared vs wild trout) and sex. Analyses were also performed on hourly and diel movement patterns and if the fish swam upstream to the first migration barrier, the power station in Spjutmo. Variation in diurnal activity was identified, with higher activity during daytime compared to night, which might be related to power production in relation to currents flowing from turbine outlets and/or the importance of daylight for effective navigation. There were no significant differences identified between hatchery-reared and wild trout, respectively, nor were there any sex-related differences. Information obtained from this study is important to understand the situation for Siljan trout, to help in future management and restoration of this valuable stock of trout.

The subject matter of this Bachelor´s thesis is the Eastern Baltic Sea cod. A literature review has been done regarding how environmental factors such as salinity, oxygen supply and temperature but also the size of the cod populations affects the migration patterns and the habitat choice of the cod. The result of the review shows that, when the eastern Baltic cod population is small, its area of distribution is restricted to the southern parts of the Baltic Sea. Moreover, high salinity leads to a larger area of distribution, while low oxygen content in the Deep Basins leads to vertical migrations, as well as further migrations south and north, to areas with better hydrological conditions. Finally the the cod tend to prefer habitats with warmer water, if the oxygen and salinity conditions are suitable, at least during the spawning period. This thesis also include estimation on how well the annual scientific trawl surveys performed by coastal Baltic countries, reflects the actual cod population size. This estimation is partly based on a critical review of available information about the trawl survey design in relation to cod migration patterns, distribution and habitat choice. Furthermore, a test has been done of how well the annual stock size estimates for the latest year, presented in the International Council for the Exploration of the Sea (ICES) Annual Reports of the Baltic Fisheries Assessment Working Group (WGBFAS), between the years 1996-2009 reflected the best available stock size estimates from 2010. The results indicate that the scientific trawl surveys might not work satisfactory. This indicates that further research must be done in the field, therefore possible alternatives such as comparisons of positioning data of commercial and scientific trawls and interviews with fishermen are suggested. / Denna uppsats handlar om torsken i det östra Östersjöbeståndet. En litteratursammanfattning har gjorts gällande hur miljömässiga faktorer såsom salthalt, syretillgång, temperatur samt storleken på bestånden påverkar migrationsmönster och habitatval hos torsken. Resultaten visar bland annat att när torskbestånden är små blir torskens utbredningsområden begränsade till de södra delarna av Östersjön. Höga salthalter leder till större utbredningsområden medan låga syrehalter i djupbassängerna leder till vertikala migrationer såväl som längre migrationer söder och norr om bassängerna, till områden med bättre syretillgång. Torsken verkar dessutom föredra habitat med varmare vatten om syre- och salthaltsförhållandena är gynnsamma, åtminstone under lekperioden. Vidare inkluderar denna uppsats en bedömning av hur väl de årliga vetenskapliga trålningsundersökningarna som utförs av länder med kust mot Östersjön, återspeglar den faktiska storleken på torskbestånden. Denna bedömning baseras på en kritisk granskning av den information som finns tillgänglig gällande de vetenskapliga trålningsundersökningarna, i förhållande till torskens migrationsmönster, distribution och habitatval. Dessutom har ett test gjorts av hur väl de årliga beståndsuppskattningarna för 1996-2009 presenterade i International Council for the Exploration of the Sea (ICES) Annual Report of the Baltic Sea Fisheries Assessment Working Group (WGBFAS), reflekterar de bästa tillgängliga beståndsuppskattningarna från 2010. Resultaten indikerar att de vetenskapliga provtrålningsundersökningarna inte fungerar tillfredsställande, vilket visar på att vidare studier måste göras inom området. Möjliga alternativ, såsom jämförelser av positioneringsdata för kommersiell- samt vetenskaplig trålning, samt intervjuer med yrkesfiskare presenteras.

Migration occurs among many animal species for the purpose of, among other things, finding food or to reproduce. Spawning migration is a form of migration that occurs among many fish species where they move to another site for reproduction. The movement can be obstructed by migration barriers like road culverts. Barriers to migration pose one of the greatest threats to biodiversity and ecosystem functions in freshwater. They impair the connectivity of watercourses and may prevent fish from improving reproductive success or completing their life histories altogether. There are both benefits and costs with migration, benefits such as increased survival for the adults and offspring, and costs such as increased energy consumption and increased mortality. The costs are often dependent on the morphological traits of the individual, like body shape and size. In this study, the spawning migration of two species of fish of the family Cyprinidae, ide (Leuciscus idus) and roach (Rutilus rutilus) was investigated. Few studies have been made on ide or on roach compared to other cyprinids and salmonids. This study might therefore enhance the overall knowledge of these two species. The overall aims of this project are to study and compare phenotypic correlates of spawning migration behaviour of ide and roach. The field studies were performed in Oknebäcken, Mönsterås (SE632310-152985), Sweden in March and April 2020. To describe the watercourse and define the location and characteristics of different potential migration barriers, a simplified biotope mapping method was used. The fish were caught in a hoop net and then measured, weighted, sexed, and injected with passive integrated transponder using the bevel down method. In order to register in stream movement of fish, reading stations with antennas were placed, at two locations upstream from the marking station and one downstream at the estuary. The sex ratio differed from the expected 1:1 with a majority of females for both species. This might be a result of fluctuations in survival of spawn coupled with different age-at-maturity between sexes. We found that individuals that arrived early to the stream were larger for both study species, as other studies also reported. Also, male ide was both larger and arrived before female ide. There might be an energy cost associated with early arrival to the stream and therefore, larger individuals arrive first. For roach, there was no difference in arrival time between the sexes although female roach were larger. There was no difference in the time spent in the stream between the species. For ide, females stayed for a longer period of time in the stream than males. However, the opposite was true for roach. This may be because male roach might benefit from more fertilization events when staying longer. There might therefore be a trade-off between the energy cost in staying in the stream and the increased fitness advantage in fertilization events. We found no correlation between any of the morphological traits and migration distance. However, since very few individuals were registered at the upstream reading stations, there might be an effect of migration barriers on the spawning migration. The mortality after spawning was higher for roach than for ide. For ide, a larger proportion of females than males died. For roach, individuals that arrived early was classified as alive to a greater extent than those who arrived late. Both similarities and differences between the species were discovered in this study which concludes that even closely related species might differ substantially from each other.