DIETARY AVAILABILITY AND RETENTION OF SELECTED MINERALS ASSOCIATED WITH THE INTENSIVE PRODUCTION OF RAINBOW TROUT (Oncorhynchus mykiss)

This research programme aimed to review the nutritional requirements for the main minerals, (namely calcium, phosphorus, magnesium and zinc) formulated in commercial diets that are essential for the health and growth performance for salmonid fish. This was undertaken with the aim of improving our knowledge of their physiology, metabolism and fate in the rainbow trout, Oncorhynchus mykiss. Phosphorous (P) featured strongly in this work due to its adverse role in pollution and the environmental impact of intensive fish farming. The first chapter surveyed the gross nutritional requirements of fish and focused on the mineral requirements in particular. Typically the P requirements for trout were found to range from 0.5-0.8% of the diet. The problems of P loading as a consequence of dietary loses was addressed and the physiological and metabolic roles of both calcium and phosphorous were especially noted in relation to fish health and for phosphorous its environmental implications were addressed. Experimental approaches were evaluated and it was decided to conduct both standard growth trial studies as well as digestibility trials to provide the basis of most investigations with the rainbow trout. Novel approaches and strategies were used in relation to specific experiments such as examining the mineral levels in blood, and various tissues and the testing of different feed ingredients, dietary supplements and mineral sources in successive investigations. Initial investigations appraised commercial diets of varying nutritional profile with respect to mineral retention and availability for rainbow trout under controlled laboratory conditions. The effects of diets containing different fishmeal sources: i.e. brown versus white fishmeals, elevated ash content and also varying in the levels of oil were tested on juvenile rainbow trout in closed recirculated systems. Diet composition caused a significant effect on mineral retention and distribution profile in fish tissues and organs. Typically, both P and Ca were of highest concentration in vertebrae of trout (60mg/g-dry weight), compared with P concentrations for all other major organs/tissues, which were fairly even between 11-20mg/g. A small increase in dietary P level (1.08% vs. 1.22%) did not affect any growth parameters for trout for the first two commercial feeds tested but there were interesting observations with respect to the amount of P excreted in the bile with a 25% increase from 0.8mM to 1.2mM. The P levels in plasma of these fish did not reflect any dietary changes. However, there was a noticeable reduction in the digestibility of P in the diet containing the white fishmeal source (26%) compared with 49% for the higher grade fishmeal diet. High ash content feeds resulted in a marked reduction in the net mineral retention of this element (16% compared to 27% for the lower ash diet). The same was also true for Ca (12% compared with 26%). The effect of oil levels in diets on mineral utilization was investigated under farmed conditions and was of particular interest given the demand for nutrient dense feeds in the industry. There was a strong tendency for improved P and Ca digestibility coefficients at each incremental increase in oil level for juvenile production sized fish (50-l00g). This ranged from 55% to over 70% when oil levels were over 26%. However this was not observed for larger fish of over 200g in weight. Experimental investigations followed are described in (Chapter 4) where fishmeal based diet was supplemented with varying levels of inorganic phosphorous. Phosphorous, calcium and other mineral absorption characteristics in addition to retention were measured in a series of growth and digestibility trials. Interestingly, there was no apparent change in the distribution of P with increasing dietary levels ranging from 1.39-2.16%. These were above known requirements for these fish with minerals being in excess. Similar results were noted for all other minerals measured in rainbow trout. There was a significant rise in the P concentration of plasma of rainbow trout fed a diet containing over 2% P and this may infer that the homeostatic regulation of P is unable to function at this level. Other haemato-logical parameters were not affected. Although not significant, there appeared to be slight trend in elevated bile P with increasing dietary P supplementation. The faecal concentrations for each of the minerals showed that elevated P in fish meal diets led to increased faecal output from 25mg/g to over 40mg/g for the highest P diet. Overall digestibility coefficients were lower as dietary P increased above that in the fishmeal control diet. These ranged from 50% to 39% for P, Ca and Mg were not greatly affected. The net retention of P was calculated and this fell from 30% to just below 20% for the range of dietary P used in the investigation. A preliminary study, reported in chapter 5A, was useful in providing information about the relative absorption profiles for differential mineral absorption from the various regions of the gastro intestinal tract of rainbow trout. A standard commercial diet was fed to large trout (>200g) and subsequently, digesta was removed from fish and analysed. For all minerals and protein, the pyloric and mid intestinal region was the main site for digestion, release and absorption of the macro elements concerned. The protein and mineral digestibility of suitable feedstuffs commonly employed in the formulation of complete diets for trout resulting from a sequence of experimental trials are presented in chapter 5B. These included a selection of marine, animal and plant by-products which were substituted into a reference basal diet designed for salmonids. This involved the inert marker- yttrium oxide and calculations based on nutrient digestibility from diet and faecal concentrations. Mineral digestibility coefficients were found to vary considerably and a number of anomalies such as negative values were obtained for Ca and Zn in certain feedstuffs. Combined diets (reference and test ingredient) gave values that were more consistent and P digestibility ranged from 47-59% in marine and animal protein concentrates compared with plant sources (24-37%). Negative values for Ca and Zn were thought to be attributable to complex interactions with other feed components. Additionally, a group of inorganic mineral supplements were tested by inclusion into a series of diets. These included mono calcium phosphate, di-calcium phosphate (DCP), mono di-calcium phosphate and magnesium phosphate. DCP produced lower Ca and P digestibility values, 31 and 50% respectively, compared with the other sources (44-62%), indicating the importance of choice of mineral supplement in aquafeeds. A critical appraisal of this work is provided in Chapter 6 and formed a retrospective review of the results generated and integrated these findings into a foundation for further research and development. Nutritional investigations using the rainbow trout as the model salmonid species raised many more questions and possibilities and broadened the scope of the topic. The subject of mineral requirements for fish is very complex and numerous factors are involved at several physiological and biochemical levels in fish. Although the research on rainbow trout involved whole animal studies under both laboratory and commercial farm conditions, the need to explore alternative in vitro methods and to utilize larger scale farm and sea cage trials for salmon were suggested. The advent of more advanced diet formulations and feeding strategies were mentioned and the scope for more scientific investigations to improve the utilization and reduce phosphorous discharge into the environment proposed.TROUW Aquaculture U

Do workplace fish tanks influence employee wellbeing and cognitive performance? An embedded mixed-methods study

Evidence from “pet-friendly” workplaces highlights potential benefits associated with taking companion animals to work, including reduced stress among employees. Ornamental fishes carry a much lower risk than other companion animals and may be a suitable alternative in situations where other animals would introduce too great a risk (e.g., allergy, accidental injury). The aim of this study was to investigate whether watching an aquarium during the working day influenced employee wellbeing through the reduction of stress and improvements in stress-related outcomes. An embedded mixed-methods study was conducted, comprising two within-subjects trials (Trials A and B) and a qualitative follow-up. Participants were university employees and research students who participated during their working day. In Trial A (n = 30), the immediate effects of watching live fishes on mood, physiological stress, and cognitive performance were compared with the effects of watching a fish video or resting quietly. Although some outcomes improved from pre- to post-activity, there was no evidence that watching fishes (live or video) had greater effects than resting quietly. In Trial B (n = 27), the effects of repeatedly engaging in the same three activities over several weeks were examined. Watching fish videos was associated with improvements in “high pleasure-low arousal” and overall job-related affective wellbeing, but no further effects of condition were found. Qualitative follow-up data collected from a subset of participants from the experimental trials (n = 13) indicated that all three activities may be beneficial as leaving their desks provided detachment from work for a short period. Qualitative data suggested that live fishes were perceived as more engaging, but this did not translate to quantitative findings. Locating fish aquaria within offices (rather than a separate workplace location) may promote wellbeing by encouraging “microbreaks”; further research is needed to investigate this hypothesis

Do Workplace Fish Tanks Influence Employee Wellbeing and Cognitive Performance? An Embedded Mixed-Methods Study

Evidence from “pet-friendly” workplaces highlights potential benefits associated with taking companion animals to work, including reduced stress among employees. Ornamental fishes carry a much lower risk than other companion animals and may be a suitable alternative in situations where other animals would introduce too great a risk (e.g., allergy, accidental injury). The aim of this study was to investigate whether watching an aquarium during the working day influenced employee wellbeing through the reduction of stress and improvements in stress-related outcomes. An embedded mixed-methods study was conducted, comprising two within-subjects trials (Trials A and B) and a qualitative follow-up. Participants were university employees and research students who participated during their working day. In Trial A (n = 30), the immediate effects of watching live fishes on mood, physiological stress, and cognitive performance were compared with the effects of watching a fish video or resting quietly. Although some outcomes improved from pre- to post-activity, there was no evidence that watching fishes (live or video) had greater effects than resting quietly. In Trial B (n = 27), the effects of repeatedly engaging in the same three activities over several weeks were examined. Watching fish videos was associated with improvements in “high pleasure-low arousal” and overall job-related affective wellbeing, but no further effects of condition were found. Qualitative follow-up data collected from a subset of participants from the experimental trials (n = 13) indicated that all three activities may be beneficial as leaving their desks provided detachment from work for a short period. Qualitative data suggested that live fishes were perceived as more engaging, but this did not translate to quantitative findings. Locating fish aquaria within offices (rather than a separate workplace location) may promote wellbeing by encouraging “microbreaks”; further research is needed to investigate this hypothesis

The effects of interacting with fish in aquariums on human health and well-being: a systematic review

BackgroundMost research into the health benefits of human-animal interaction has focused on species that interact physically with humans, such as dogs. This may be unsuitable for certain populations for reasons including accessibility and the risk of negative consequences to both the person and the animal. However, some research has associated viewing fish in aquariums with positive well-being outcomes; as there is no physical contact with the animal, this form of interaction carries less risk. At present, little is known about the specific benefits of human-fish interaction.ObjectivesTo explore current evidence relating to the psychological and physiological benefits of interacting with fish in aquariums.MethodsSystematic searches were conducted to identify relevant primary research of any design. All forms of interaction were considered, including keeping fish as companion animals and fish aquarium-based interventions. “Non-live” alternatives, such as videos, were also considered. This review was conducted according to a registered protocol (PROSPERO ID: CRD42018090466).ResultsNineteen studies were included. Two provided tentative evidence that keeping home aquaria is associated with relaxation. The remaining studies involved novel interactions with fish in home or public aquariums. Outcomes relating to anxiety, relaxation and/or physiological stress were commonly assessed; evidence was mixed with both positive and null findings. Preliminary support was found for effects on mood, pain, nutritional intake and body weight, but not loneliness. All studies had methodological issues and risk of bias was either high or unclear.ConclusionsReview findings suggest that interacting with fish in aquariums has the potential to benefit human well-being, although research on this topic is currently limited. Future research should aim to address gaps in the evidence, such as whether and how the type of human-fish interaction can influence well-being outcomes. Researchers should also aim to address the methodological concerns highlighted in this review

Companion animal type and level of engagement matter: a mixed-methods study examining links between companion animal guardianship, loneliness and well-being during the covid-19 pandemic

To reduce the spread of COVID-19, countries worldwide placed limitations on social interaction, which is anticipated to have severe psychological consequences. Although findings are inconsistent, prior research has suggested that companion animals may positively influence human well-being and reduce loneliness. In the context of COVID-19, this has important implications, as companion animal guardians may be less negatively affected by the pandemic. The primary aim of this research was to investigate the influence of companion animals on mental well-being and loneliness during the pandemic, with specific interest in the role of ornamental fishes. A mixed-methods study was conducted, using an international sample. Quantitative data were collected via an online survey (n = 1199) and analysed using robust hierarchical multiple regression analyses; the influence of level of engagement with companion animals was examined for dogs, cats and ornamental fishes. There was no evidence that companion animal guardianship was associated with loneliness and mental well-being during the pandemic but spending more time engaging physically or socially with dogs (and to a lesser extent cats) was generally associated with poorer outcomes. Qualitative data were collected through open-ended survey responses (n = 757) and semi-structured interviews (n = 25) and analysed using reflexive thematic analysis. Two themes were developed—one related to companion animals as providers of social and emotional support, and the other to companion animals as providers of purpose and perspective. Concerns regarding the impact of the pandemic on animal welfare were also identified. Compared to other animal types, more participants expressed indifference regarding the impact of their fishes on their well-being during the pandemic, possibly because fishes cannot provide comfort via physical touch. The findings of this study reflect the wider field of human–animal interaction; although qualitative data suggest guardians believe their companion animals are a positive influence in their lives, there is little convincing quantitative data to support these beliefs. This highlights the need to refine theories regarding which aspects of companion animal guardianship may influence human well-being; the findings from this research may be useful in the refinement of such theories

The effect of substrate on water quality in ornamental fish tanks

SIMPLE SUMMARY: Fish kept as pets are almost always held in tanks with substrate such as gravel or sand on the bottom of the tank. This may be added as a form of enrichment to encourage natural fish behaviours, or for aesthetic reasons. However, substrate can also harbour elevated levels of waste products and unwanted bacteria; therefore, whether the use of substrate in home aquaria is advantageous or disadvantageous has not been fully considered. Here, we investigated whether there was a difference in water quality in home aquaria that contained either no substrate (bare tanks), plastic plants as enrichment but no substrate, sand or gravel substrate. Water quality (e.g., temperature, oxygen, pH and ammonia) and the presence of bacteria were measured over a 7-week period. As water quality can also vary with the season, the study was repeated at different times of the year. Addition of both gravel and sand substrate resulted in increased pH and the waste products ammonia and nitrate. Substrate was also associated with a greater presence of bacteria. In conclusion, the use of substrate affected water quality, with further research needed on the use of substrate in home aquaria. ABSTRACT: Almost all home aquaria contain substrate, either as intentional enrichment or for aesthetic purposes. For fishes, benefits of structural enrichment have been well considered, particularly in research and aquaculture settings. However, our understanding of the impacts of tank substrate as enrichment is limited. While substrate can induce foraging in some species, a major drawback is the potential of substrate to harbour elevated levels of waste and pathogenic bacteria. Here, we considered whether substrate as a form of environmental enrichment significantly altered water quality and bacterial presence in home aquaria. Water quality (temperature, oxygen, pH, TAN, unionised ammonia, nitrate, Ca(2+), Na(+), Mg(2+) and K(+)) and bacterial presence (Pseudomonas spp.) were measured over two seven-week periods in stand-alone, tropical, freshwater tanks that simulated home aquaria. The following four enrichment conditions were considered: bare tanks, plastic plants, gravel substrate or sand substrate. The addition of both gravel and sand resulted in increased pH, concentrations of total ammonia nitrogen and nitrate. Substrate was also associated with a greater Pseudomonas presence. Decreased pH alongside an increased concentration of ions were also observed depending on the time of year. In conclusion, enrichment type affected the water quality of home aquaria, with further research needed on the role of the tank biome in fish welfare