Traditionally, fish oil (FO) has been used extensively in aquafeeds. The stagnation in global fish oil production coupled with an increased demand for its use in aquaculture feeds, especially salmonid feeds, has greatly inflated fish oil prices. Therefore, in order to sustain the rapid growth of the tilapia industry, the dependence on these commodities in feeds should be reduced through use of cheaper and more sustainable sources of dietary lipids, such as palm oil. This study therefore investigated several, previously poorly understood, effects of palm oil on reproductive performance of the commercial tilapia species, Oreochromis niloticus; which currently ranks as second most popular species in world aquaculture. In the present study broodstock were fed on experimental diets at full and half ration regimes throughout their entire life cycle from exogenous feeding. Studies were conducted in standardised and controlled hatchery conditions, thereby reducing the potential influence of environmental variations. First feeding O. niloticus fry were fed on four diets, cod liver oil (D 1), palm oil (D 2), mixed palm and cod liver oil (D 3) (9:1 ration) and a commercial trout diet as control (D 4) (Skretting, U.K.) on a reducing ration based on fish size. The present study investigated the effect of dietary lipid sources on (1) growth performance, (2) biochemical composition of eggs (total lipid and fatty acid composition), (3) morphological parameters of eggs (total and relative fecundity, egg size, egg weight and EW:BW), (4) larval quality (larval length and weight) and (5) oocyte recruitment and its associated sex steroid hormones. Experimental diets and feeding ration significantly influenced (p<0.05) the growth performance over a period of 120 days. Total lipid and fatty acid composition of eggs originating from broodstock fed on palm oil, mixed palm and cod liver oil (9:1) or a control diet were not significantly different (P>0.05) when fed at either full (3% BWday-1) or half ration (1.5% BWday-1). The present study, however, confirmed that fatty acid composition of fish eggs reflected the fatty acid composition of the diet, although specific fatty acids were selectively utilized or retained in the eggs. The mean inter-spawning interval (ISI) increased with increasing fish size and averaged 14, 19 and 24 days for fish fed on palm oil, mixed palm and cod liver oil or control diets, respectively. The shortest ISI observed was 7 days for fish fed a palm oil diet. Total fecundity ranged from 660 - 820 eggs/clutch. Mean total fecundity was 750, 820 and 660 eggs/clutch for fish fed a palm, mixed palm and cod liver oil or a control diet, respectively, but these differences were not significant (P>0.05). However, relative fecundity and egg weight to body weight rates as a percentage (EW: BW) were found significantly differ (p<0.05) between fish fed the control diet and experimental diets. Mean egg diameter (2.2 mm) was not significantly influenced (p>0.05) by experimental diets. The egg volume, egg dry and wet weight, fertilisation and hatching rate were also not significantly different between fish fed the experimental diets. Oocyte development was classified into distinct stages based upon oocyte size, biochemical properties and structure. The recrudescence to these stages was not significantly influenced by broodstock fed experimental diets either at full or half ration. Steroid hormones and histological analyses provided valuable data concerning the oocyte development and recruitment in this species. Levels of 17ß-oestradiol (E2) and testosterone (T) peaked within 6 days of spawning, suggesting that vitellogenesis began as early as day 2 or 3 post-spawning. By day 6, ovaries were dominated by large late-vitellogenic/maturing oocytes (stages 6 & 7) occupying about 70% of the ovary. Gonadosomatic index (GSI) reached maximal levels by day 6. It is suggested that pre-vitellogenic oocytes are recruited into vitellogenic growth immediately after spawning and complete vitellogenesis on day 6 post-spawning. Finally, the present study investigated the effect of food restriction at two rations (full and half) on broodstock reproductive performance. Oreochromis niloticus were rationed from first feeding and throughout their life-cycle. The dietary regime, full ration (3%) and half ration (1.5%), influenced fish size but despite this variation no significant differences (p>0.05) were detected in total lipid and fatty acid composition in the eggs, total fecundity, egg diameter, total egg volume and larval size. These results suggested that despite large differences in food availability throughout their life cycle, investment in reproduction had remained remarkably consistent. It appeared that during food restriction, O. niloticus sacrificed body weight and growth so as to maintain reproductive investment. In summary, this study provides valuable information using a novel experimental design on the effects of dietary lipid sources on reproductive performance of female O. niloticus. Substituting palm oil for fish oil as the dietary lipid source and reducing ration by half (1.5% BWday-1) had no significant effect on reproductive performance. Therefore it is suggested that under controlled conditions, lipids of non-marine origin, such as palm oil, can be successfully substituted for broodstock diets. Halving feed requirement should also increase profitability of seed production. KEYWORDS: Tilapia; O. niloticus; palm oil; diet; fecundity; spawning periodicity; oocyte recruitment; reproductive performance.

The main objective of this dissertation was to evaluate long-term fluctuations in the distribution and abundance of Engraulis anchoita eggs and larvae in the Southeastern Brazilian Bight (SBB). Engraulis anchoita is a fish species that is ecologically and economically important. We analyzed samples and abiotic data from eighteen oceanographic cruises conducted during austral late spring and early summer from 1974 to 2010. Two different stocks were detected in the SBB based on egg size, with the predominant stock in the area having smaller eggs than the stock in the region further south. Using indicative kriging, we identified occasional (e.g. Florianópolis - 27°S and off Santos Bay) and avoided (e.g. off São Sebastião Island and off Cananéia-Iguape Coastal System) spawning sites. Through zero-inflated models, spatial factors (different areas and the local depth) were related to the probability of sampling false zeros and temporal and oceanographic conditions (different years and temperature) with egg and larvae abundance. We also described faster and more accurate methodology to identify E. anchoita eggs, and compared the mesh-size efficiency to sample eggs and analyzed how egg size varied seasonally. Our results may support future studies and may assist a future fishery management of E. anchoita, a species not yet exploited in the SBB. / O principal objetivo dessa tese foi analisar as flutuações de longo-prazo na distribuição e abundância de ovos e larvas de Engraulias anchoita, uma espécie de peixe de importância econômica e ecológica, na Plataforma Continental Sudeste do Brasil (PCSE). Nós analisamos amostras e dados abióticos de dezoito cruzeiros oceanográficos realizados durante o fim da primavera e o começo do verão de 1974 a 2010. Dois estoques distintos foram identificados com base no tamanho dos ovos, um predominante e com menor tamanho e outro de maior tamanho ao sul da PCSE. Através de \"krigagem\" indicativa, foram identificadas áreas de desova ocasional (como ao norte de Florianópolis e a área ao largo da baía de Santos) e áreas em que a desova foi evitada (como em frente à Ilha de São Sebastião e ao Sistema Costeiro Cananéia-Iguape). Usando modelos inflacionados de zeros, os fatores espaciais (diferentes áreas e profundidades amostradas) foram relacionados com a probabilidade de se amostrar falso zero, enquanto os fatores temporais e oceanográficos (diferentes anos e temperatura) foram relacionados com a abundância de ovos e larvas. Apresentamos também uma metodologia mais rápida e mais eficiente para identificar os ovos de E. anchoita, comparamos as amostragens realizadas com duas malhagens diferentes e analisamos variações sazonais do tamanho dos ovos capturados. Assim, nossos resultados poderão auxiliar estudos futuros e também no manejo pesqueiro da espécie em questão, ainda não explorada comercialmente na área de estudo.

The main objective of this dissertation was to evaluate long-term fluctuations in the distribution and abundance of Engraulis anchoita eggs and larvae in the Southeastern Brazilian Bight (SBB). Engraulis anchoita is a fish species that is ecologically and economically important. We analyzed samples and abiotic data from eighteen oceanographic cruises conducted during austral late spring and early summer from 1974 to 2010. Two different stocks were detected in the SBB based on egg size, with the predominant stock in the area having smaller eggs than the stock in the region further south. Using indicative kriging, we identified occasional (e.g. Florianópolis - 27°S and off Santos Bay) and avoided (e.g. off São Sebastião Island and off Cananéia-Iguape Coastal System) spawning sites. Through zero-inflated models, spatial factors (different areas and the local depth) were related to the probability of sampling false zeros and temporal and oceanographic conditions (different years and temperature) with egg and larvae abundance. We also described faster and more accurate methodology to identify E. anchoita eggs, and compared the mesh-size efficiency to sample eggs and analyzed how egg size varied seasonally. Our results may support future studies and may assist a future fishery management of E. anchoita, a species not yet exploited in the SBB. / O principal objetivo dessa tese foi analisar as flutuações de longo-prazo na distribuição e abundância de ovos e larvas de Engraulias anchoita, uma espécie de peixe de importância econômica e ecológica, na Plataforma Continental Sudeste do Brasil (PCSE). Nós analisamos amostras e dados abióticos de dezoito cruzeiros oceanográficos realizados durante o fim da primavera e o começo do verão de 1974 a 2010. Dois estoques distintos foram identificados com base no tamanho dos ovos, um predominante e com menor tamanho e outro de maior tamanho ao sul da PCSE. Através de \"krigagem\" indicativa, foram identificadas áreas de desova ocasional (como ao norte de Florianópolis e a área ao largo da baía de Santos) e áreas em que a desova foi evitada (como em frente à Ilha de São Sebastião e ao Sistema Costeiro Cananéia-Iguape). Usando modelos inflacionados de zeros, os fatores espaciais (diferentes áreas e profundidades amostradas) foram relacionados com a probabilidade de se amostrar falso zero, enquanto os fatores temporais e oceanográficos (diferentes anos e temperatura) foram relacionados com a abundância de ovos e larvas. Apresentamos também uma metodologia mais rápida e mais eficiente para identificar os ovos de E. anchoita, comparamos as amostragens realizadas com duas malhagens diferentes e analisamos variações sazonais do tamanho dos ovos capturados. Assim, nossos resultados poderão auxiliar estudos futuros e também no manejo pesqueiro da espécie em questão, ainda não explorada comercialmente na área de estudo.

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.

In den vergangenen Jahren ist es zu einer dramatischen Vervielfachung der verfügbaren Rechenzeit gekommen. Diese 'Grid Ressourcen' stehen jedoch nicht als kontinuierlicher Strom zur Verfügung, sondern sind über verschiedene Maschinentypen, Plattformen und Betriebssysteme verteilt, die jeweils durch Netzwerke mit fluktuierender Bandbreite verbunden sind. <br /> Es wird für Wissenschaftler zunehmend schwieriger, die verfügbaren Ressourcen für ihre Anwendungen zu nutzen. Wir glauben, dass intelligente, selbstbestimmende Applikationen in der Lage sein sollten, ihre Ressourcen in einer dynamischen und heterogenen Umgebung selbst zu wählen: Migrierende Applikationen suchen eine neue Ressource, wenn die alte aufgebraucht ist. 'Spawning'-Anwendungen lassen Algorithmen auf externen Maschinen laufen, um die Hauptanwendung zu beschleunigen. Applikationen werden neu gestartet, sobald ein Absturz endeckt wird. Alle diese Verfahren können ohne menschliche Interaktion erfolgen.<br /> Eine verteilte Rechenumgebung besitzt eine natürliche Unverlässlichkeit. Jede Applikation, die mit einer solchen Umgebung interagiert, muss auf die gestörten Komponenten reagieren können: schlechte Netzwerkverbindung, abstürzende Maschinen, fehlerhafte Software. Wir konstruieren eine verlässliche Serviceinfrastruktur, indem wir der Serviceumgebung eine 'Peer-to-Peer'-Topology aufprägen. Diese “Grid Peer Service” Infrastruktur beinhaltet Services wie Migration und Spawning, als auch Services zum Starten von Applikationen, zur Dateiübertragung und Auswahl von Rechenressourcen. Sie benutzt existierende Gridtechnologie wo immer möglich, um ihre Aufgabe durchzuführen. Ein Applikations-Information- Server arbeitet als generische Registratur für alle Teilnehmer in der Serviceumgebung.<br /> Die Serviceumgebung, die wir entwickelt haben, erlaubt es Applikationen z.B. eine Relokationsanfrage an einen Migrationsserver zu stellen. Der Server sucht einen neuen Computer, basierend auf den übermittelten Ressourcen-Anforderungen. Er transferiert den Statusfile des Applikation zu der neuen Maschine und startet die Applikation neu. Obwohl das umgebende Ressourcensubstrat nicht kontinuierlich ist, können wir kontinuierliche Berechnungen auf Grids ausführen, indem wir die Applikation migrieren. Wir zeigen mit realistischen Beispielen, wie sich z.B. ein traditionelles Genom-Analyse-Programm leicht modifizieren lässt, um selbstbestimmte Migrationen in dieser Serviceumgebung durchzuführen. / In recent years, there has been a dramatic increase in available compute capacities. However, these “Grid resources” are rarely accessible in a continuous stream, but rather appear scattered across various machine types, platforms and operating systems, which are coupled by networks of fluctuating bandwidth. It becomes increasingly difficult for scientists to exploit available resources for their applications. We believe that intelligent, self-governing applications should be able to select resources in a dynamic and heterogeneous environment: Migrating applications determine a resource when old capacities are used up. Spawning simulations launch algorithms on external machines to speed up the main execution. Applications are restarted as soon as a failure is detected. All these actions can be taken without human interaction. <br /> <br /> A distributed compute environment possesses an intrinsic unreliability. Any application that interacts with such an environment must be able to cope with its failing components: deteriorating networks, crashing machines, failing software. We construct a reliable service infrastructure by endowing a service environment with a peer-to-peer topology. This “Grid Peer Services” infrastructure accommodates high-level services like migration and spawning, as well as fundamental services for application launching, file transfer and resource selection. It utilizes existing Grid technology wherever possible to accomplish its tasks. An Application Information Server acts as a generic information registry to all participants in a service environment. <br /> <br /> The service environment that we developed, allows applications e.g. to send a relocation requests to a migration server. The server selects a new computer based on the transmitted resource requirements. It transfers the application's checkpoint and binary to the new host and resumes the simulation. Although the Grid's underlying resource substrate is not continuous, we achieve persistent computations on Grids by relocating the application. We show with our real-world examples that a traditional genome analysis program can be easily modified to perform self-determined migrations in this service environment.

Fish sound production has been associated with courtship and spawning behavior. Acoustic recordings of fish sounds can be used to identify distribution and behavior. Passive acoustic monitoring (PAM) can record large amounts of acoustic data in a specific area for days to years. These data can be collected in remote locations under potentially unsafe seas throughout a 24-hour period providing datasets unattainable using observer-based methods. However, the instruments must withstand the caustic ocean environment and be retrieved to obtain the recorded data. This can prove difficult due to the risk of PAMs being lost, stolen or damaged, especially in highly active areas. In addition, point-source sound recordings are only one aspect of fish biogeography. Passive acoustic platforms that produce low self-generated noise, have high retrieval rates, and are equipped with a suite of environmental sensors are needed to relate patterns in fish sound production to concurrently collected oceanographic conditions on large, synoptic scales. The association of sound with reproduction further invokes the need for such non-invasive, near-real time datasets that can be used to enhance current management methods limited by survey bias, inaccurate fisher reports, and extensive delays between fisheries data collection and population assessment. Red grouper (Epinephelus morio) exhibit the distinctive behavior of digging holes and producing a unique sound during courtship. These behaviors can be used to identify red grouper distribution and potential spawning habitat over large spatial scales. The goal of this research was to provide a greater understanding of the temporal and spatial distribution of red grouper sound production and holes on the central West Florida Shelf (WFS) using active sonar and passive acoustic recorders. The technology demonstrated here establishes the necessary methods to map shelf-scale fish sound production. The results of this work could aid resource managers in determining critical spawning times and areas. Over 403,000 acoustic recordings were made across an approximately 39,000 km2 area on the WFS during periods throughout 2008 to 2011 using stationary passive acoustic recorders and hydrophone-integrated gliders. A custom MySQL database with a portal to MATLAB was developed to catalogue and process the large acoustic dataset stored on a server. Analyses of these data determined the daily, seasonal and spatial patterns of red grouper as well as toadfish and several unconfirmed fish species termed: 100 Hz Pulsing, 6 kHz Sound, 300 Hz FM Harmonic, and 365 Hz Harmonic. Red grouper sound production was correlated to sunrise and sunset, and was primarily recorded in water 15 to 93 m deep, with increased calling within known hard bottom areas and in Steamboat Lumps Marine Reserve. Analyses of high-resolution multibeam bathymetry collected in a portion of the reserve in 2006 and 2009 allowed detailed documentation and characterization of holes excavated by red grouper. Comparisons of the spatially overlapping datasets suggested holes are constructed and maintained over time, and provided evidence towards an increase in spawning habitat usage. High rates of sound production recorded from stationary recorders and a glider deployment were correlated to high hole density in Steamboat Lumps. This research demonstrates the utility of coupling passive acoustic data with high-resolution bathymetric data to verify the occupation of suspected male territory (holes) and to provide a more complete understanding of effective spawning habitat. Annual peaks in calling (July and August, and November and December) did not correspond to spawning peaks (March - May); however, passive acoustic monitoring was established as an effective tool to identify areas of potential spawning activity by recording the presence of red grouper. Sounds produced by other species of fish were recorded in the passive acoustic dataset. The distribution of toadfish calls suggests two species (Opsanus beta and O. pardus) were recorded; the latter had not been previously described. The call characteristics and spatial distribution of the four unknown fish-related sounds can be used to help confirm the sources. Long-term PAM studies that provide systematic monitoring can be a valuable assessment tool for all soniferous species. Glider technology, due to a high rate of successful retrieval and low self-generated noise, was proven to be a reliable and relatively inexpensive method to collect fisheries acoustic data in the field. The implementation of regular deployments of hydrophone-integrated gliders and fixed location passive acoustic monitoring stations is suggested to enhance fisheries management.

Στην παρούσα εργασία πραγματοποιήθηκε εκτίμηση της αναπαραγόμενης βιομάζας του ευρωπαϊκού γαύρου, Engraulis encrasicolus, στην περιοχή του Βορειοανατολικού Αιγαίου (Θρακικό Πέλαγος, Κόλπος Καβάλας, Στρυμωνικός Κόλπος, Λήμνος) τα έτη 2003 και 2004 με τη Μέθοδο Ημερήσιας Παραγωγής Αβγών (DEPM). Για την εφαρμογή της μεθόδου πραγματοποιήθηκαν δύο ωκεανογραφικά ταξίδια με το Ε/Σ «ΦΙΛΙΑ» κατά το μέγιστο της ωοτοκίας του γαύρου τον Ιούνιο του 2003 και του 2004. Στη διάρκεια τους συλλέχθηκαν δείγματα ιχθυοπλαγκτού για την εκτίμηση της ημερήσιας παραγωγής αβγών, ενώ πραγματοποιήθηκαν και λήψεις κατακόρυφων διατομών θερμοκρασίας και αλατότητας σε εκτεταμένο δίκτυο σταθμών. Παράλληλα, πραγματοποιήθηκαν δειγματοληψίες ενήλικων ατόμων γαύρου είτε επί του επαγγελματικού στόλου των γρι-γρι της περιοχής, είτε με την πελαγική τράτα του «ΦΙΛΙΑ», τα οποία χρησιμοποιήθηκαν για την εκτίμηση της αναλογίας φύλου, της γονιμότητας ομάδας, της συχνότητας ωοτοκίας και του μέσου βάρους των θηλυκών. Όσον αφορά στις περιβαλλοντικές συνθήκες, το 2003 παρατηρήθηκε αυξημένη στρωματοποίηση των υδάτων, χαμηλότερη επιφανειακή αλατότητα και υψηλότερες τιμές χλωροφύλλης-α, διαφορές που πιθανώς οφείλονται σε αυξημένη εκροή νερού της Μαύρης Θάλασσας. Και τα δύο έτη η βιομάζα του ζωοπλαγκτού ήταν περίπου ίδια. Μέσω απλής ανάλυσης πηλίκου για το χαρακτηρισμό του αναπαραγωγικού ενδιαιτήματος του γαύρου, βρέθηκε ότι και τις δύο χρονιές η ωοτοκία πραγματοποιήθηκε σε νερά με χαμηλή αλατότητα (<34.5), πλούσια σε χλωροφύλλη-α και ζωοπλαγκτό. Αντίθετα, τα θερμοκρασιακά εύρη κατά τις δύο χρονιές διέφεραν, γεγονός που φαίνεται να αντανακλά περισσότερο τις διαφορές θερμοκρασίας ανάμεσα στα δύο έτη παρά διαφορετική προτίμηση για ωοτοκία. Επιπλέον, το 2004 η παραγωγή αβγών ήταν μειωμένη, το πεδίο αναπαραγωγής είχε συρρικνωθεί και η ωοτοκία ήταν επικεντρωμένη στην περιοχή του Θρακικού. Για την εκτίμηση της συχνότητας ωοτοκίας πραγματοποιήθηκε ιστολογική ανάλυση των θηλυκών γονάδων του γαύρου, από την οποία προέκυψε ότι ενώ τα στάδια ανάπτυξης των υγιών ωοκυττάρων ήταν παρόμοια με περιγραφές για το είδος Engraulis mordax, τα στάδια της ατρησίας παρουσίασαν ορισμένες διαφορές. Αυτές αφορούσαν στην εμφάνιση καφε-κίτρινων χρωστικών (χαρακτηριστικό γνώρισμα της δ-ατρησίας) στο τέλος της β-ατρησίας. Επιπλέον, η απορρόφηση των κενών ωοθυλακίων διαρκούσε δύο ημέρες σε αντίθεση με παρατηρήσεις για το Engraulis mordax, όπου παρατηρούνταν και κενά ωοθυλάκια τριών ημερών, διαφορά που οφείλεται στις υψηλότερες θερμοκρασίες του ΒΑ. Αιγαίου σε σχέση με περιοχές αναβλύσεων. Οι παράμετροι των ενηλίκων που προέρχονταν από δείγματα της επαγγελματικής και πειραματικής αλιείας δεν εμφάνισαν σημαντικές διαφορές μεταξύ τους. Αντίθετα, διαφορές παρατηρήθηκαν ανάμεσα στα δύο έτη όσον αφορά στις παραμέτρους του μέσου βάρους, της συχνότητας ωοτοκίας και της γονιμότητας. Συγκεκριμένα, το 2004 τα ψάρια ήταν βαρύτερα, πιο εύρωστα και απελευθέρωναν μεγαλύτερο αριθμό αβγών ανά μικρότερα χρονικά διαστήματα. Αν λάβει κανείς υπ’όψιν ότι το 2004 η αναπαραγόμενη βιομάζα ήταν σημαντικά μικρότερη ενώ η βιομάζα του ζωοπλαγκτού παρέμεινε η ίδια, οι παραπάνω διαφορές μπορούν να εξηγηθούν από φαινόμενα εξάρτησης των παραμέτρων αυτών από την πυκνότητα του πληθυσμού (density dependence). Η αναπαραγόμενη βιομάζα το 2004 (6251t) ήταν σημαντικά μειωμένη και αντιστοιχούσε σχεδόν στο 1/3 της βιομάζας του 2003 (17600t). Η μείωση αυτή πιθανώς να οφείλεται σε συνδυασμό έντονης αλιευτικής πίεσης και χαμηλών επιπέδων στρατολόγησης της ηλικιακής κλάσης του 2003. / The spawning biomass of the European anchovy, Engraulis encrasicolus, stock in the N.E. Aegean Sea was estimated by means of the Daily Egg Production Method (DEPM) for the years 2003 and 2004. Two oceanographic surveys were conducted with the R/V “PHILIA” during the maximum reproductive activity of the anchovy population in June 2003 and 2004. Ichthyoplankton sampling and vertical profiles of temperature and salinity were performed over an extensive grid of stations. At the same time adult anchovy samples were collected either on board the commercial purse-seine fleet or by means of an experimental pelagic trawl operated by “PHILIA”. The adult samples were used to estimate parameters of the DEPM: sex ratio, mean female weight, batch fecundity and spawning frequency. Significant interannual differences were found in the environmental conditions. In June 2003 the water column was more stratified, less saline (5m) and richer in chlorophyll-α, which probably were due to larger outflow of Black Sea Water (BSW). The zooplankton biomass remained the same during 2003 and 2004. A simple quotient rule analysis was applied to characterize the spawning habitat of anchovy. In both years anchovy spawning appeared to take place in less saline waters (34.5), rich in chlorophyll-α and zooplankton. On the contrary, anchovy spawning appeared to take place over different temperature range in the two years. This rather reflects different temperature values in 2003 and 2004 than different selection for spawning. In 2004 the daily egg production was reduced, the spawning area was limited and the spawning activity took place mainly in the Thracian Sea. Histological analysis of the female anchovy gonads was carried out in order to estimate the spawning frequency. The developmental stages of healthy oocytes were similar to those of the species Engraulis mordax. However, the atresia stages were different with regard to the appearance of brown-yellow pigments at the end of beta stage atresia instead of the end of delta stage atresia. Moreover, the absorption of the postovulatory follicle lasted two days instead of three days. The higher temperatures in the N.E. Aegean Sea were responsible for the shorter duration of the postovulatory follicle absorption. There were no statistically significant differences between DEPM adult parameters calculated from purse-seine samples compared to pelagic trawl samples. On the contrary, mean female weight, fecundity and spawning frequency showed statistically significant differences between the two years. In 2004 the anchovies were in better condition and produced numerous eggs in short interspawning intervals. Since the estimated biomass was lower in 2004 while the zooplankton biomass remained stable, it seems that density-dependence phenomena could justify the interannual differences. The estimated spawning biomass in 2004 (6251t) was significantly lower compared to that of 2003 (17600t). Intense fishing effort and low levels of recruitment of the 2003 cohort are probably responsible for this decrease.

Environmental factors influence species and habitats on multiple scales creating a mosaic of distribution patterns. Studying factors shaping these patterns are central to our understanding of population dynamics and ultimately ecosystem functioning. Information on the distribution of resources and conservation values are also highly needed in marine management as coastal areas are increasingly influenced by human activities. In this thesis, large-scale field data is used to explore how strong environmental gradients found on multiple scales in the coastal areas of the Baltic Sea influence fish habitats. The underlying concepts are based in the field of species distribution modelling, whereby habitat maps can be produced using environmental layers in a geographic information system. Distribution modelling is further used to address both ecological and applied questions by examining effects of habitat limitation on fish population sizes and to evaluate management actions aimed at habitat conservation. I show that specific habitat requirements for fish species of both freshwater and marine origin can be described using environmental variables and that species-environment relationships can be used to predict the distribution of early life-stages of fish in the Baltic Sea archipelagos. Further, predicted habitat availability of a specific life-stage was directly related to adult population size of Eurasian perch Perca fluviatilis, signifying that the abundance of large predatory fish can be limited by specific recruitment habitats. Lastly, by predicting the distribution of an assemblage of coastal fish species and their associated habitats, an assessment of a network of marine protected areas was performed. Results revealed large gaps in the current network and identified areas suitable for future protection. By demonstrating how current habitat protection can be improved by including critical habitats for coastal fish population sizes this thesis points to the benefits of integrating nature conservation and fisheries management. Based on these findings I conclude that species distribution modelling provides a suitable analytical framework for assessing the habitat requirements of organisms. An increased understanding of habitat-population relationships and an ability to accurately map ecologically important features will be of great value for an ecosystem-based marine management. ­ / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 709

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