Behavioural and physiological studies of fighting in male Tilapia Zillii (Cichlidae)

This thesis is a compilation of several behavioural and physiological studies of fighting in a species of African cichlid fish, Tilapia zillii. The behavioural studies are concerned with explaining the functional significance and behavioural organisation of fighting. The physiological studies are concerned with attempting to elucidate the mechanisms that underlie the expression of aggressive behaviour. My aim is show how these two levels of study are related and why it is important to maintain a balance between them in the study of animal behaviour.Chapter 2 reports a senes of laboratory experiments that investigated how asymmetries in body size and gonadal state influence the fighting strategies of male T. zillii, Fights between animals over limited resources often end in victory to the larger contestant. Game theory predicts that relative body size is assessed during the fight and thus also determines fight duration and intensity. However, if the contestants differ in the value they place on the disputed resource, this can override the effects of relative body size. In the experiment described here, relative gonad weight was a much stronger predictor of fight outcome than relative body size. This suggests that males with large gonads fight harder to defend their territory, implying that the value of a territory is a function of the gonadal state of the individual. Despite this, a detailed behavioural analysis suggested that relative body size is assessed through a behaviour termed 'mouth wrestling'. In addition to persisting in the fight, smaller contestants escalated to a higher degree (in terms of biting), especially if they went on to win the tight. Winners and losers differed consistently with regard to a behaviour termed mouth locking, suggesting that through this behaviour the fish were assessing an asymmetry related to the intention to persist with the fight, although I could not demonstrate that this was related to relative gonad weight.Chapter 3 was undertaken with the aim of gaining information on the social structure and occurrence of aggressive behaviours in a semi-natural environment. To this end, a study was made of the social interactions of a group of male fish allowed free range over approximately ten metres of artificial 'river bed' during a four week period. Under these conditions, the social structure of T. zillii may be described as a loose group with an unstable dominance hierarchy. Aggression is a major component of this species' time budget, with different acts and degrees of escalation probably functioning to establish, challenge and maintain dominance relationships within the hierarchy. The expression of territorial behaviour appeared to be conditional upon social status (only the two top ranked males were seen to dig nests and consistently court females). One escalated fight was observed between the two highest ranked fish, but it was not clear whether this was a territorial dispute, a challenge for the top position, or a dispute over both. Thus, while the immediate reasons for escalated fighting between male T. zillii depends upon the social and physical environment, it is probably ultimately caused by competition for mating opportunities. Chapter 4 deals with the issue of how body size and gonadal state relate to life-history aspects of the animal by means of a morphometric analysis. The analysis provided evidence to suggest that there was a trade off between gonad size and the storage of fat It is not clear whether this relationship arises from a direct energetic trade-off or is a result of adopting different behavioural strategies. I also explored the relationship between behaviour, morphology and somatic and reproductive condition. It was possible to predict gonadal state on the basis of mouth morphology which may explain why so much fighting involves use of the mouth in this species.In Chapter 5 I studied the proximate costs of fighting in terms of physical injury and the metabolic consequences of engaging in a energetically demanding activity. In relation to injuries incurred during fights, losers suffered greater scale loss than winners, especially if the loser was larger than its opponent. In relation to energy metabolism, fighting resulted in significant depletion of total sugar reserves from the muscle and the liver (compared to unfought controls). It appears that the muscle energy reserves are respired anaerobically, as was evident from the accumulation of lactate in the muscle. Interestingly, losers had significantly higher levels of lactate than winners. Together, the data on injury and metabolic state suggest that fighting is costly for both winners and losers, but that this is especially marked for losers. These data are discussed in relation to models of animal decision-making and it is concluded that the summation of different proximate costs incurred during fighting is likely to underlie the making of decisions such as continuing, giving up or escalating the fight.In Chapter 6 I report a study of plasma concentrations of gonadal steroids in T. zillii in relation to fighting and gonadal state. The gonadal steroids, particularly the androgens, have been shown to be associated with aggression in a wide range of species and seemed like obvious candidates for the mechanism by which gonadal state influences behaviour Blood samples were taken from fish immediately after fighting and the plasma concentrations of the following gonadal steroids were then determined by radioimmunoassay: testosterone (T), l l-ketotestosterone (1IkT) and 17a,20~- Dihydroxy-4-pregnen-3-one (17,20-P) and estradiol (Ez). T concentrations did not correlate with GSI and no differences were detected between winners, losers and unfought controls. II kT concentrations were on average twice those of T and negatively correlated to GSI, although winners, losers and controls were not significantly different. T and II kT concentrations were positively correlated with each other but 17,20-P and Ez levels were too low to be accurately measured. It appears that in T. zillii, II kT is the major androgen as it is in most other mature male teleosts.While the present results suggest that these sex steroids may playa role in physiological regulation of testicular maturation, they do not support the idea that these steroids are the mechanism by which GSI influences aggressive behaviour. In Chapter 7 I review the main conclusions of the previous chapters. I then offer my personal opinion on how the different levels and approaches taken throughout the study interrelate and collectively reinforce each other and why integration between disciplines is important in the study of animal behaviour

Deep Sea – Close Kin: A Genetic Approach for Improved Fisheries Management

Deep-sea fish stocks consist of species that live at depths of greater than 400 metres. While being important for EU fisheries, this natural renewable resource is particularly vulnerable to over-fishing, as many deep sea species are slow-growing and commonly of low fecundity. Generally little is known about the biology of deep sea species, and there prevails a substantial lack of scientific data on deep-sea stocks. This constitutes a major impediment to management strategies underpinning sustainable and profitable deep sea fisheries. Europe’s deep-sea fisheries began in the 1970’s and were entirely unregulated. The fleet grew as rewards were high, but many species were rapidly depleted. It was only in 2003 that a management plan was brought into action. While some measures to better protect commercially exploited deep sea fish have been adopted, such as the limitation of fishing effort or total allowable catches, these have been insufficient to allow stocks to recover and there is a general consensus that most deep-water stocks remain below safe biological limits for exploitation. In a recent communication to the Council and the European Parliament, the European Commission has emphasized the need to improve our knowledge on deep sea fish species to move away from the current prevailing unsustainable exploitation. Ideally, this would be the development of a robust and practical approach to estimate the abundance of deep sea species to support stock assessments and reduce the uncertainty about the state and rebuilding rates of commercially exploited deep sea stocks. The current rapid technology development and concurrent steep drop in costs of large-scale genotyping offers major opportunities for fisheries management. This report explores whether the concept of genetic close-kin abundance estimation, recently applied to establish biomass estimates of Southern Bluefin Tuna, can be applied to fisheries management of deep sea fish species.JRC.G.3-Maritime affair

Using individual tracking data to validate the predictions of species distribution models

The authors would like to thank the College of Life Sciences of Aberdeen University and Marine Scotland Science which funded CP's PhD project. Skate tagging experiments were undertaken as part of Scottish Government project SP004. We thank Ian Burrett for help in catching the fish and the other fishermen and anglers who returned tags. We thank José Manuel Gonzalez-Irusta for extracting and making available the environmental layers used as environmental covariates in the environmental suitability modelling procedure. We also thank Jason Matthiopoulos for insightful suggestions on habitat utilization metrics as well as Stephen C.F. Palmer, and three anonymous reviewers for useful suggestions to improve the clarity and quality of the manuscript.Peer reviewedPostprintPostprintPostprintPostprintPostprin

Seasonal and ontogenetic variation in depth use by a critically endangered benthic elasmobranch and its implications for spatial management

The project was undertaken through the Movement Ecology of the Flapper skate project at St Andrews and received support from the Ecology and Conservation Group, Marine Scotland Science, and Marine Scotland Planning & Policy and NatureScot. It was funded by Marine Scotland projects SP004 and SP02B0 and NatureScot project 015960.Seasonal and ontogenetic variation in depth use by benthic species are often concomitant with changes in their spatial distribution. This has implications for the efficacy of spatial conservation measures such as Marine Protected Areas (MPAs). The critically endangered flapper skate (Dipturus intermedius) is the designation feature of an MPA in Scotland. This species is generally associated with deeper waters >100 m; however, little is known about its seasonal or ontogenetic variation in habitat use. This study used archival depth data from 25 immature and mature flapper skate tagged in the MPA over multiple years. Time series ranged from 3 to 772 (mean = 246) days. Generalised additive mixed models and highest density intervals were used to identify home (95%) and core (50%) highest density depth regions (HDDRs) to quantify depth use in relation to time of year and body size. Skate used a total depth range of 1 – 312 m, but home HDDRs typically occurred between 20 – 225 m. Core HDDRs displayed significant seasonal and ontogenetic variation. Summer core HDDRs (100 – 150 m) suggest high occupancy of the deep trenches in the region by skate of most size classes. There was an inverse relationship between body size and depth use, and a seasonal trend of skate moving into shallow water over winter months. These results suggest flapper skate are not solely associated with deep water, as skate, especially large females, are frequently found in shallow waters (25 – 75 m). The current management, which protects the entire depth range, is appropriate for the protection of flapper skate through much of its life-history. This research demonstrates why collecting data across seasonal scales and multiple ontogenetic stages is needed to assess the effectiveness of spatial management.Publisher PDFPeer reviewe

A Scientific Basis for Regulating Deep-Sea Fishing by Depth

The deep sea is the world’s largest ecosystem [1], with high levels of biodiversity [2, 3] and many species that exhibit life-history characteristics that make them vulnerable to high levels of exploitation [4]. Many fisheries in the deep sea have a track record of being unsustainable [5, 6]. In the northeast Atlantic, there has been a decline in the abundance of commercial fish species since deep-sea fishing commenced in the 1970s [7, 8]. Current management is by effort restrictions and total allowable catch (TAC), but there remain problems with compliance [9] and high levels of bycatch of vulnerable species such as sharks [10]. The European Union is currently considering new legislation to manage deep-sea fisheries, including the introduction of a depth limit to bottom trawling. However, there is little evidence to suggest an appropriate depth limit. Here we use survey data to show that biodiversity of the demersal fish community, the ratio of discarded to commercial biomass, and the ratio of Elasmobranchii (sharks and rays) to commercial biomass significantly increases between 600 and 800 m depth while commercial value decreases. These results suggest that limiting bottom trawling to a maximum depth of 600 m could be an effective management strategy that would fit the needs of European legislations such as the Common Fisheries Policy (EC no. 1380/2013) [11] and the Marine Strategy Framework Directive (2008/56/EC) [12]

Depth as a driver of evolution in the deep sea: Insights from grenadiers (Gadiformes: Macrouridae) of the genus Coryphaenoides

Here we consider the role of depth as a driver of evolution in a genus of deep-sea fishes. We provide a phylogeny for the genus Coryphaenoides (Gadiformes: Macrouridae) that represents the breadth of habitat use and distributions for these species. In our consensus phylogeny species found at abyssal depths (> 4000 m) form a well-supported lineage, which interestingly also includes two non-abyssal species, C. striaturus and C. murrayi, diverging from the basal node of that lineage. Biogeographic analyses suggest the genus may have originated in the Southern and Pacific Oceans where contemporary species diversity is highest. The abyssal lineage seems to have arisen secondarily and likely originated in the Southern/Pacific Oceans but diversification of this lineage occurred in the Northern Atlantic Ocean. All abyssal species are found in the North Atlantic with the exception of C. yaquinae in the North Pacific and C. filicauda in the Southern Oceans. Abyssal species tend to have broad depth ranges and wide distributions, indicating that the stability of the deep oceans and the ability to live across wide depths may promote population connectivity and facilitate large ranges. We also confirm that morphologically defined subgenera do not agree with our phylogeny and that the Giant grenadier (formally Albatrossia pectoralis) belongs to Coryphaenoides, indicating that a taxonomic revision of the genus is needed. We discuss the implications of our findings for understanding the radiation and diversification of this genus, and the likely role of adaptation to the abyss

Development and Evaluation of Methods for Surveying Fish Populations in Nearshore Waters

Nearshore areas provide critical habitat for a range of fish species targeted by commercial and recreational fisheries, both of which make an important contribution to local economies in rural areas. However, established trawl survey methods are not suited to many nearshore areas, owing to shallow depths, obstructions on the sea bed or vulnerable habitats, so there is a lack of information on fish abundance in these areas. The aim of the present project was to develop and test survey methods applicable to Scottish inshore waters, focussing on baited underwater cameras, fish traps, systematic rod-and-line surveys and observations of fish bycatch in crustacean trap fisheries, and to carry out associated studies of fish movements. A lightweight baited underwater camera system was developed that could be deployed by two persons from inshore fishing vessels and small boats. The system consisted of a digital camera and strobes in underwater housings, mounted on a frame of aluminium alloy tubing, suspended above the seabed by sub-surface floats on one leg of a J-shaped mooring. The camera was baited with oily fish and a standardized 1 hour deployment period was used, to minimize variability in results due to changing tidal currents and bait degradation. Photographs were taken at 30 second intervals throughout the deployment period. On retrieval, the photographs were examined to derive indices of fish abundance, such as the time to first arrival of particular species (TFA) and the maximum number of individuals seen in the field of view at any time during the deployment (MaxN). The BUC system was developed and tested in the Firth of Clyde and then deployed at a range of other locations in Lamlash Bay, Arran, the Firth of Lorn, the Sound of Mull, Loch Sunart, Loch Etive, around Skye, Galloway and in Orkney. The BUC system was successfully deployed from a range of types of vessel in depths down to 40 m. Over thirty species of fish were recorded in total, including species of commercial interest, with lesser spotted dogfish, Scyliorhinus canicula, being the most commonly recorded. The number of species and indices of abundance were highest at sites on the Galloway peninsula. When compared within a single area, BUC detected more species than angling or fish traps, but less than in visual transects by SCUBA divers. BUC shows great potential as a cost-effective survey method, able to show relative differences in abundance between areas. It is likely that it would also be effective in detecting temporal trends, though this was outside the scope of the present project. A Norwegian design of collapsible cod trap, Roscoff traps designed for common prawns and Norway lobster creels were investigated as fish traps. There were differences in catch rates and species composition related to the trap design. Roscoff traps appeared to be suitable for sampling juvenile cod (Gadus morhua) in complex habitat in shallow water, whereas collapsible cod traps are suitable for larger fish, but need to be fished in greater numbers to obtain sufficient data. Creel fisheries were surveyed by questionnaire and by on-board catch sampling. A range of fish species is taken as bycatch in creels, with some obvious differences in species composition between crab fishing and Norway lobster fishing in relation to the depths and ground types fished. The present results suggest that the catch rates of commercial fish species may be too low for creeling to be a useful way of monitoring fish stocks, but sampling throughout the year in different areas would be desirable to assess this more fully. A small-scale pilot study in Galloway indicated some potential for rod-and-line surveys to generate useful information on the abundance of certain fishes. The Scottish Sea Angling Conservation Network and the Scottish Shark Tagging Project already collect information on catches of angling target species and on tagging and recaptures of tagged fish. This would be augmented by encouraging anglers to submit returns with an indication of fishing duration even when they have not caught anything. However, we were unsuccessful in recruiting volunteers to participate in a randomized angling survey. Further work is required to develop statistically robust angling surveys in which volunteer anglers would be willing to participate. Experience indicates that payment of expenses would be required for volunteers to agree to fish according to a survey protocol. To study movements of a species of interest to recreational sea anglers, spurdog (Squalus acanthias), ten specimens in Loch Etive were tagged with data storage tags designed to record water temperature and depth. To date, one tag has been recovered and the downloaded data shows an interesting pattern of nocturnal movements into shallow water. More information should become available when more of the tagged spurdog are recaptured. The following recommendations arise from the present study: To improve our understanding of baited methods of surveying fish and to develop improved estimates of abundance, modelling studies of bait odour dispersal and fish responses are required, building on previous work in this area. Further trials of baited underwater cameras at different sites and under different conditions are required to assess the degree of variability in the different types of abundance index that can be derived. Further work to compare different survey methods is required at sites with greater fish abundance, e.g. at sites around the Galloway peninsula. A BUC system with greater depth limit (e.g. 200 m) should be developed to extend the range of habitats in which it can be used to include other species of interest. Further work is required to assess the size and species selectivity of different designs of fish trap. An intensive pilot survey of an area of interest, such as an actual or proposed marine protected area, by BUC and fish traps would provide a good test of the ability of these methods to generate data of use to inshore fishery managers and conservation interests. Seasonal sampling of fish bycatch in Norway lobster and crab creel fisheries is desirable to further assess the potential for creel fisheries to be used to monitor fish populations. Ongoing analysis of recreational sea-angling catch and tagging records should be encouraged and supported by Marine Scotland. There should be continued engagement between recreational sea-anglers and fishery scientists in Marine Scotland and universities

Distribution and thermal niche of the common skate species complex in the north-east Atlantic

Temperature is one of the most significant variables affecting the geographic distribution and physiology of elasmobranchs. Differing thermal gradients across a species' range can lead to adaptive divergence and differing developmental times, an important consideration for recruitment rates of exploited species. The Critically Endangered common skate (formerly Dipturus batis) has been divided into 2 species, the flapper skate D. intermedius and blue skate D. batis, both of which have undergone dramatic population declines. Here we examine the environmental thermal and geographic distribution of these species, using observations from scientific trawling surveys and recreational angling around the British Isles. As similar-sized specimens of the 2 species can be confused, we validated species identity using molecular genetic techniques. Both species had more extensive geographic ranges than previously reported and different spatial patterns of abundance. The distribution of the blue skate appears to reflect its partiality to thermally less variable and warmer waters, while flapper skate were found in more variable and notably colder areas. The thermal range and current geographic distribution of these species indicate that future projected climate change could have a differential impact on distribution of flapper and blue skate in the north-east Atlantic

Ontogenetic Variation in Movements and Depth Use, and Evidence of Partial Migration in a Benthopelagic Elasmobranch

Tope (Galeorhinus galeus) is a highly mobile elasmobranch in the temperate to subtropical northeast Atlantic. It is highly migratory and has been shown to display complex movement patterns, such as partial migration, in the southern hemisphere. In the northeast Atlantic, previous mark-recapture studies have struggled to identify movement patterns and the species behavior is poorly described, yet identification of migratory behaviors and habitats of importance for the species is of paramount importance for effective management. Here, we combined fisheries independent survey data with mark-recapture (MR) data to investigate the distribution of different age classes of tope across the northeast Atlantic. We further investigated depth use in detail with archival electronic tags and a pop-up satellite archival tag (PSAT). We suggest previous studies struggling to find consistent movement patterns using MR data were confounded by a combination of site fidelity, partial migration by females, and increasing depth and home range of juveniles. Survey and MR data showed immature tope <40 cm were caught exclusively in continental shelf waters <45 m deep, showing a significant relationship between habitat depth and total length. Immature individuals seemed to remain on the continental shelf, while mature tope of both genders were caught in both shelf and offshore waters. This use of deeper water habitats by mature tope was further supported by archival tags, which indicated individuals use both shallow (<200 m depth) and deep-water habitats, diving to depths of 826 m; the deepest record for this species. The PSAT tag tracked the horizontal movements of an adult male, which confirmed utilization of both shallow inshore and deep offshore habitats. Most tope remained within 500 km of their tagging site, although some mature females had a larger, more southerly range, including connectivity with the Mediterranean. This study clearly demonstrates the highly migratory habits of tope, and suggests larger individuals divide their time between shallow and deep-water habitats. It shows the northeast Atlantic tope population should benefit from consistent management throughout its range