Jokiravun ja täpläravun aktiivisuus, rohkeus ja eksploratiivisuus : käyttäytymiserojen toistuvuus ja sukupuolen vaikutus

Jokirapu (Astacus astacus) on Suomessa alkuperäislaji. Rapuruttoa hyvin sietävää täplärapua (Pacifastacus leniusculus) on istutettu lähinnä Etelä-Suomeen vuodesta 1967 lähtien. Täplärapu on kookkaampi, aggressiivisempi ja lisääntymiskykyisempi kuin jokirapumme. Yleensä täplärapu dominoi jokirapua, kun rapujen elinympäristöt kohtaavat. Täpläravun dominoivaa otetta voidaan selittää tiettyjen käyttäytymispiirteiden ollessa korreloituneena. Tietyt käyttäytymispiirteet voidaan liittää yleisesti tulokaslajien dominoivaan levittäytymiseen uusille alueille. Tulokaslajin täytyy levittäytyä epäröimättä, lisääntyä hyvin pienestä alkupopulaatiosta huolimatta sekä runsastuessaan aiheuttaa suuria vaikutuksia tunkeutumaansa yhteisöön. Tulokaslajiin käyttäytymisessä voisi siis olla korreloituneena aktiivisuus, rohkeus ja eksploratiivisuus. Käyttäytymissyndroomalla viitataan korreloituneisiin yksilön yhdenmukaisiin käyttäytymispiirteiden eroihin, jotka ilmenevät tietyssä tilanteessa ja/tai läpi tiettyjen kontekstien. Kontekstilla tarkoitetaan toiminnallista käyttäytymiseen liittyvää kategoriaa (esim. levittäytyminen). Populaatio tai laji voi ilmentää käyttäytymissyndroomaa. Jokaisella yksilöllä on oma käyttäytymistyyppinsä käyttäytymissyndrooman sisällä. Saman käyttäytymistyypin omaavien yksilöiden käyttäytyminen korreloi muiden yksilöiden käyttäytymisen kanssa järjestysluvullisen arvoasteikon mukaan. Käyttäytymissyndroomat voivat vähentää käyttäytymiseen liittyvää plastisuutta tai ylläpitää yksilöiden käyttäytymisen välistä vaihtelua. Pro gradu –työni tavoitteeni on tutkia joki- ja täplärapujen käyttäytymiseroja. Olen valinnut tutkimuksen kohteeksi aktiivisen, rohkean ja eksploratiivisen käyttäytymisen, joiden korrelaatioita on jo löydetty muutamilla lajeilla. Tutkin käyttäytymiserojen toistuvuutta sekä sukupuolen vaikutusta. Oletin löytäväni positiivisen korrelaation aktiivisessa, rohkeassa ja eksploratiivisessa käyttäytymisessä ravuilla (käyttäytymissyndrooma), ja oletin näiden käyttäytymispiirteiden välisten erojen olevan täpläravuilla suuremmat. Käyttäytymispiirrekokeet suoritin Viikissä kahteen kertaan käyttäytymisen toistuvuuden testaamiseksi. Käyttäytymisen toistuvuus osoittautui melko hyväksi, vaikka jälkimmäisen kokeen (=samaa käyttäytymistä mittaava koe tehty toiseen kertaan) tulokset olivatkin usein merkitsevästi erilaisia ensimmäisen kokeen tuloksiin verrattuna. Aktiivisuus toistui hyvin käyttäytymispiirrekokeiden kesken. Jokirapujen aktiivisena olo aika on suurempi kuin täpläravuilla aktiivisuuskokeessa ja eksploratiivisuuskokeessa. Täplärapujen aktiivisuus yleensä nousi jälkimmäisessä, kun taas jokirapujen aktiivisuus laski. Sukupuoleen sidottuja käyttäytymiseroja ei juurikaan löytynyt. Rohkeaa ja eksploratiivista käyttäytymistä ilmentävät kokeet osoittautuivat epäonnistuneiksi mittaamaan näitä käyttäytymispiirteitä. En voi saamieni tulosten perusteella todeta joki- tai täpläravuilla olevan käyttäytymissyndroomaa, jossa aktiivisuus, rohkeus ja eksploratiivisuus olisivat korreloituneena

Factors influencing diurnal activity of crayfish and its seasonality

Crayfish is mainly but not exclusively a nocturnal animal. The crayfish aktivity is taxon specific and can be further affected by various factors. The aim of this thesis is to create an overview of factors affecting the activity and to summarize their impact. Factors can be divided into those influencing daily activity and those influencing seasonal behaviour. This thesis focuses on discussing different reactions to the factors and its intensity by individual species. Insufficient data covering activity during the winter season offers an opportunity for further research. Key words: crayfish; daily activity; abiotic factors; biotic factors; seasonalityRaci jsou živočichové s převážně, ale ne výhradně, noční aktivitou. Aktivita raků je specifická pro konkrétní taxony a může být dále ovlivňována mnoha faktory. Cílem této bakalářské práce je vytvořit přehled faktorů a shrnout dostupné informace o jejich působení. Faktory mohou být rozděleny do kategorií ovlivňující každodenní aktivitu a ovlivňující sezónní změny. V práci se zaměřuji na rozdílnou reakci konkrétních druhů na tyto faktory a také rozdílnou intenzitu působení jednotlivých faktorů. Nedostatek dat potřebných pro bližší porozumění zimní aktivitě dává prostor k dalšímu výzkumu. Klíčová slova: raci; každodenní aktivita; abiotické faktory; biotické faktory; sezonalitaKatedra ekologieDepartment of EcologyFaculty of SciencePřírodovědecká fakult

Overland Movement and Activity of the Endangered White-Clawed Crayfish Austropotamobius Pallipe

The UK’s only native crayfish, the white-clawed crayfish Austropotamobius pallipes, is endangered and in decline across its range in Europe. The principle threat derives from the introduction, accidental and deliberate, of invasive crayfish species, which lead to losses of native crayfish through transmission of crayfish plague Aphanomyces astaci and competitive exclusion. Conservation programmes for white-clawed crayfish include captive breeding and conservation translocations. Crayfish are able to move terrestrially and this thesis examined the potential of white clawed crayfish to make terrestrial movements within an experimental arena. Results were compared with experiments on two UK invasive crayfish species, the signal crayfish Pacifastacus leniusculus and the red swamp crayfish Procambarus clarkii. White-clawed crayfish proved surprisingly willing to move onto a terrestrial environment, with 65% of animals tested making an exit from the water. Fewer signal crayfish and red swamp crayfish exited, but those that did, exited more frequently and spent longer in the terrestrial environment than white-clawed crayfish. An immediate and important outcome of these findings is to review captive enclosure design. Many more white-clawed crayfish made exits onto the terrestrial bridge when tested singly, than when in groups of four. This suggests a negative density-dependence in which crayfish are assessing habitat quality through the presence of conspecifics, or that when alone they make different behavioural decisions than when kept with conspecifics. White-clawed crayfish were tested in groups of four at varying sex ratios to investigate changes in activity level and interactions. Three metrics were captured: number of crayfish active in a group, how active the focal animal was, and number of interactions between the focal animal and its conspecifics. Size proved significant across the metrics, with larger animals showing less activity, taking part in fewer interactions, and a large size range corresponding to less activity in a group. This demonstrates the importance of using size in models of behaviour within crayfish, even when using size matched animals as seen here. Activity levels within the experimental tank corresponded with sex ratios. Having a higher percentage of males corresponded with more activity in the tank and female only trials were the least active groups. This is hypothesised to be due to the more agonistic nature of male crayfish and is despite the finding that overall males were slightly less active than females. Both sexes responded to the sex ratio of the system which consisted of four experimental tanks running through the same water system. Both sexes were more active when there were more males in the system. The finding that crayfish activity levels corresponded with sex ratios of animals they were only in aquatic contact with indicates they are responding to pheromones, which is relevant to aquarists and researchers alike. Overall this thesis found interesting differences in native and invasive species behaviours, and some thought-provoking intrinsic and extrinsic factors relating to activity levels

Microhabitat use and recolonisation in white-clawed crayfish: application to conservation

White-clawed crayfish Austropotamobius pallipes are listed as vulnerable on the International Union for the Conservation of Nature (IUCN) red list and British populations represent one of the greatest concentrations of this species in Europe. White-clawed crayfish still remain at risk in Britain due to habitat degradation, pollution, and non-indigenous crayfish and disease. This thesis investigates the microhabitat use of juvenile and adult white-clawed crayfish and quantifies the rate and pattern of recolonisation into an unoccupied reach of river. The microhabitat study was carried out over a 1 km stretch of the River Wansbeck, Northeast England in 2008 and a 3.5 km stretch on the Hart Burn, a tributary of the Wansbeck, in 2009. In September 2008 there was a 1 in 115 year flood and the data collected before and after the flooding were compared. Crayfish recorded in the Wansbeck were separated into three age groups, 0+ (0 - 9.4 mm carapace length (CL)), 1+ (9.5 - 16.4 mm CL) and 2+ and older (16.5 mm+ CL). Crayfish recorded in the Hart Burn were separated into four age groups 0+ (0 - 7.4 mm), 1+ (7.5 - 13.4 mm), 2+ (13.5 - 22.4 mm) and 3+ and older (22.4 mm+). Crayfish of different ages had different microhabitat requirements where young crayfish, in particular 0+ crayfish, were more restricted in the microhabitats they inhabited. Young crayfish were found in closer proximity to the bank, in smaller substrata and slower velocities than older crayfish. In both study sites substratum heterogeneity created suitable habitat for all ages of crayfish and in the Hart Burn, root habitats were found to be important for all ages of crayfish. Extensive flooding in 2008 was found to significantly reduce densities of larger crayfish, probably reflecting large-scale mortalities or major redistribution. Recolonisation was studied in the lower 3 km of the Hart Burn after a mass mortality event occurred in May 2004, apparently due to a one-off acute pollution incident. The recolonisation data highlights the impact mass mortality events can have on crayfish populations. It took 4 years of no further pollution for the population to recover which relates to a recolonisation rate of 750 m year-1. The passive downstream drift of juveniles was the most rapid form of movement recorded and was responsible for the downstream population expansion in the first two years. Juvenile crayfish seem to have some control over their dispersal, as there was limited dispersal over periods of high flows and rapid dispersal over periods of low flows. Active upstream and downstream dispersal by adult crayfish was similar in rate

Transforming a Research Concept into Commercial Practice: Addressing the ‘Hurdles’ of Single-Species eDNA-based Detection

The use of environmental DNA (eDNA) for measuring and monitoring biodiversity has been identified as a novel molecular based method to complement more commonly utilised traditional ecological sampling techniques. It is a time and cost-efficient technique, which is rapidly advancing due to the capabilities of low eDNA detection levels. As the efficiency of the technique has increased, commercial organisations and end-users have gained a greater interest in its application. Despite this, the technique is currently only commercially available from a select few service providers. In the UK, the main target species for commercial scale eDNA-based detection is the great crested newt (Triturus cristatus). Interest has now been sparked for the development of eDNA assays to detect various other species, both for use as a regulated informative tool and a conservation aid. However, many recent studies have highlighted various limitations associated with the use of eDNA-based detection and this appears to be hampering commercialisation of this tool. eDNA-based detection methods remain relatively underdeveloped and un-validated for use as reliable and accurate widespread monitoring programs and other such applications. Here, the so called ‘hurdles’ associated with the development and validation of eDNA-based methods and its use as a fully available commercial service are reviewed and addressed, in order to develop and validate a commercially applicable eDNA assay for the endangered white-clawed crayfish, Austropotamobius pallipes, as a target organism. When designing novel species-specific assays, detailed validation steps need to be undertaken, ensuring they perform under various conditions, habitats, and which sampling methods should be utilised. Currently, more traditional methods used to asses populations of white-clawed crayfish (such as trapping and hand searching) are becoming increasingly more difficult to undertake as the species become rarer and populations more fragmented. Such techniques are therefore expensive (with regard to time spent surveying) and often result in low probability of detection. A new species-specific qPCR assay to detect white-clawed crayfish was developed and tested under various conditions both ex-situ (laboratory and mesocosms) and in-situ (ponds and rivers) to explore the optimum sampling strategy giving the most reliable results. Experiments were also conducted on a wider scale to determine the impact of DNA degradation and seasonal influence on eDNA persistence. Interestingly, this thesis illustrates that sample collection choice is not simple, and the ‘best’ methodology was shown to vary between habitat type. This indicates that great care should be taken when designing any such assays and implementing them in the field. Furthermore, this study highlights that a ‘standard operating procedure’ for eDNA-based detection in the commercial sector may not be possible and this will have to be explored on an assay by assay basis. Alongside case studies from real-world application of the technique, recommendations are made on how this novel eDNA assay can be used for the commercial practice of white-clawed crayfish assessment.SureScreen Scientific

The Ecology of Signal Crayfish in Two Large Ultra-Oligotrophic Ecosystems: Crater Lake and Lake Tahoe

Invasive species have become an increasing problem in the Western United States particularly when there are multiple stressors (e.g., invasive species and eutrophication) occurring to ecosystems. Invasive omnivores can present unique problems for aquatic ecosystems by having both direct and indirect impacts on native benthic invertebrates and vertebrates. Omnivorous crayfish, for example, strongly influence littoral habitats and biota with their foraging habits, creating both direct and indirect effects on trophic interactions in aquatic systems. Once they invade, these crayfish can ultimately dominate freshwater ecosystems. This dissertation investigates the distribution, density changes, and the direct and indirect impacts of the invasive signal crayfish (Pacifastacus leniusculus) in two oligotrophic lentic ecosystems in the western United States; Lake Tahoe (CA-NV) and Crater Lake (OR). In chapter 1, I investigate the distribution, movement, and feeding behavior of invasive signal crayfish in Crater Lake. This lake population presents a unique opportunity to understand the movement of crayfish in a recently expanding population. I used minnow traps and snorkeling to determine crayfish distribution and stable isotope ratios of δ13C and δ15N to determine the flow of organic matter through the food web, trophic position, and percent benthic reliance. Depth gradient minnow traps demonstrate that crayfish densities can live as deep as 250 m. Trap and snorkel surveys from 2008 to 2013 indicate an expansion of crayfish from 44% to 78% of the littoral zone. Summer water temperature in Crater Lake has been warming, which may increase the recruitment of individuals and expand habitat availability for growth. Between 1965 and 2014 the nearshore surface temperature increased by 3.5°C. Principal component analysis revealed a positive relationship between crayfish occupation and cobble and boulder habitats of the lake. Crayfish in the littoral zone rely heavily (97.4%) on littoral-benthic carbon sources indicating their potential for impacting native invertebrate communities and the overall dynamics of Crater Lake’s ecosystem. Our findings indicate, however, that deeper water crayfish also may rely on littoral benthic energy resources. Crayfish movement to deeper waters may be subsidizing generally nutrient poor, deep-water habitats with littoral energy through excretion and egestion, where physical conditions are stable and natural perturbation is low.In Chapter 2, I quantify the influence of this early, expanding invasion in Crater Lake to littoral zone ecology by evaluating their influence on zoobenthic consumer biomass and basal algal biomass. Benthic invertebrate biomass was 77% lower in hard substrate and 78% lower in soft substrate areas with crayfish present than in crayfish-absent locations. Using Bayesian, stable isotope mixing models, dietary preferences of crayfish at three locations with varying crayfish densities were quantified. Only slight variations in crayfish diet were detected between the three locations where crayfish have been established, the outer boundary of crayfish expansion, and the middle of the crayfish population indicating that crayfish. Despite differing densities, crayfish are feeding on similar food sources, particularly benthic invertebrates. At low crayfish densities (0 to 10), benthic invertebrate numbers were 222.3±36.6 individuals m-2, while chlorophyll a was 16.8±5.8 mg m-2. At high densities of crayfish (>50), benthic invertebrates had low mean density 3.0±4.2 individuals m-2, while chlorophyll a biomass was high 226.7±48.1 mg m-2. Crayfish are impacting native invertebrate communities and periphyton biomass in Crater Lake by changing trophic interactions in the lake’s littoral zone and altering the lake’s food web.In Chapter 3, I focus on the benthic environment and biodiversity of Lake Tahoe and regional lakes (Donner Lake, Marlette Lake, and Fallen Leaf Lake. Signal crayfish were introduced into the Central Sierra Nevada region of the United States in the late 19th to early 20th century. I used a long-term data set to document highly variable crayfish densities in the littoral zone of Lake Tahoe, showing an increase during the summer months linked to an increase in water temperature (R2 = 0.69, P<0.001). Crayfish responded to site-specific characteristics of the nearshore rather than to lake-wide characteristics; local stream discharge was the only factor that explained a positive increase in lake densities (P< 0.04). Trophic niche models developed from stable isotope measurements of crayfish and nongame fish indicate that crayfish influence the dietary breadth (e.g. niche area) of nongame fish consumers. Crayfish feeding behavior may be forcing nongame fish to feed on a broader set of food resources when crayfish are present. Stable isotope analysis also indicates an overlap of crayfish niche area with other nongame fish and amphibians, indicating interspecific competition between organisms. Our study highlights that local factors influence cold-water crayfish movement and densities in large lakes, as well as potential direct and indirect influences on nongame fish consumers in the littoral region, potentially affecting native biota and ecosystem function. This research has significant implications for understanding the direct and indirect impacts of signal crayfish in oligotrophic food webs, particularly on benthic invertebrate densities. It expands on the current understanding of expansion of signal crayfish and the factors that influence crayfish density. Future research will need to focus on better understanding the life history and mechanisms controlling this species if they are to be controlled in lakes of the Western United States

New approaches for exploring signal crayfish invasion biology and ecological impacts in headwater streams

The global spread of invasive alien species has had severe ecological, social and economic implications, with freshwater systems proving particularly vulnerable to invasion. Freshwater crayfish are exceptionally successful invaders, and 90% of species introduced to Europe have become established in the wild. As ecosystem engineers, crayfish present a significant threat to aquatic ecosystems. However, methodological constraints have thus far limited our understanding of invasive crayfish ecology and environmental impacts. This project aims to better our understanding of the spatio-temporal ecological impact invasive crayfish have on native biota, using Bookill Gill Beck and Long Preston Beck in the Yorkshire Dales as a case study. A novel method was developed to produce quantitative data on crayfish populations along an invasion gradient from well-established sites to the invasion front, where native crayfish still persist. The method was rigorously tested to evaluate efficiency and optimal deployment time for both crayfish and benthic fish. Following proof-of-concept, the method was then used to explore the invasion ecology and ecological impacts of signal crayfish within the headwater system. Population demographics of signal crayfish were investigated along the invasion gradient over three subsequent field seasons (2018 - 2020), focussing on population density, size structure and biomass, including relationships with substrate composition. Subsequently, density- dependent impacts of signal crayfish on macroinvertebrate and fish communities were explored, comparing sites along the invasion gradient and temporal changes at individual sites over the three-year timeframe. Notable changes in macroinvertebrate community composition and severe declines of native fish were observed, with European bullhead the most affected fish species. The results of this research can be used to inform conservation and management decisions by greatly enhancing our understanding of the invasion biology and ecological impacts of invasive crayfish, whilst also offering a novel method to be used in quantitative population assessments in future research and monitoring

Crayfish in Scotland

Unlike the rest of Britain, Scotland has no native crayfish species. There are, however, two introduced species: the white-clawed crayfish (Austropotamobius pallipes) has inhabited Loch Croispol in Sutherland and Whitemoss Reservoir in Renfrewshire for several decades. A. pallipes is endangered in its native range and Scottish stocks may constitute an important conservation resource in the future. The other crayfish species in Scotland, the North American signal crayfish (Pacifastacus leniusculus) was first recorded in the wild in 1995 and has spread rapidly to inhabit many river catchments and standing waters, where it is considered a serious threat to native biodiversity. The purpose of this thesis was to conduct research into the distribution, control and impact of non-native crayfish in Scotland, with a main focus on P. leniusculus. A comparative field study on the River Clyde in southern-central Scotland was used to test the efficacy of different sampling methods for detecting P. leniusculus in shallow, flowing waters. A combination of kick-sampling and three-run electrofishing was shown to be the most effective method and assisted in the development of a crayfish detection protocol. This protocol has been applied by fishery trusts across Scotland to determine the fine-scale distribution of P. leniusculus in rivers. Results of a radio-tracking study in the River Clyde catchment showed that P. leniusculus moves up to 195 m day -1 in lotic habitats, with flow and in-stream barriers identified as potential impediments to movement. In addition to studies of P. leniusculus, surveys were undertaken to assess the status of the two A. pallipes populations in Scotland. Results showed the occurrence of a low density and high density population at Loch Croispol and Whitemoss Reservoir respectively. These sites could serve as long-term “ex-situ” ark sites for A. pallipes but only if measures are taken to mitigate the current biosecurity threats of P. leniusculus and disease. Laboratory studies were used to assess the potential threat of P. leniusculus to Atlantic salmon (Salmo salar) redds and the globally endangered freshwater pearl mussel (Margaritifera margaritifera). The burial of Salmo salar eggs in redds appears to afford protection from predation by P. leniusculus but other life stages may be at greater risk. Crayfish attempted to predate upon M. margaritifera but were unsuccessful, probably due to the thick, protective shell of the adult mussels tested; predation of juvenile mussels is predicted to be more likely. Finally, the impact of a large-scale trapping programme on a population of P. leniusculus in a large lake was evaluated using mark and recapture methods at Loch Ken in southern Scotland. The programme significantly reduced the number of males in the population but its effect on females was complicated by seasonal variation in trappability and the bias of traps towards males. Depth was found to be a significant determinant of the catch of P. leniusculus. Animals were also found to make significant movements of 800 metres in two weeks. Crayfish occur in Loch Ken at densities which are high compared with other lakes and the loss of native biodiversity there is expected to be considerable. Continued research into invasive species such as P. leniusculus will provide valuable data to support management decisions and help tackle what is one of the top five drivers of human-induced global change