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, Ca²⁺, Na⁺, Mg²⁺ 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.

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

Simple Summary

Companion animals (pets) may reduce loneliness and promote the well-being of their guardians (owners). This is important in the context of the COVID-19 pandemic, as companion animal guardians may be less negatively affected by the pandemic. This research examined the influence of companion animals, and specifically ornamental fishes, on mental well-being and loneliness during the pandemic. Data were collected via an online survey and interviews with companion animal guardians. Companion animal guardianship alone was not linked to loneliness or well-being during the pandemic, but there was evidence that people who interacted more with their dogs (and to a lesser extent cats) were lonelier and had poorer well-being; possibly, these individuals spent more time with their dogs/cats because they were more isolated. Open-ended survey responses and interview data identified that most people felt their companion animals were a positive influence during the pandemic, but ornamental fishes were perceived as having a less positive effect than other companion animals, possibly because they cannot provide comfort via physical touch. Consistent with past research, these findings indicate that people believe their companion animals positively influenced their lives during the pandemic, but there is a lack of quantitative evidence to support these beliefs.

Abstract

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.

First report of the infectious spleen and kidney necrosis virus (ISKNV) infection in ornamental fishes in India

Infectious spleen and kidney necrosis virus (ISKNV), a member of family iridoviridae, reported for the first time in a wide range of ornamental fish species in India. Significant mortalities during the year 2018-19 were reported from a number of retailers in the region with various clinical signs. The samples of moribund, dead and apparently healthy ornamental fishes were collected from retailers, located in three districts of Karnataka, India. Out of 140 fish samples, 16 samples (11.42%) representing 10 different fish species were found positive to ISKNV by OIE listed primers and same samples were reported to amplify the major capsid protein (MCP) gene of ISKNV. Further, sequence analysis of MCP gene showed that all strains detected in this study were closely related to other documented isolates from different countries with an identity ranging from 98.76% to 100%. Further, they clustered in the clade of ISKNV, during the phylogenetic analysis. The sequence similarity was high (99.94%) to ISKNV strains from Japan, Australia and Malaysia. This is the first report of an ISKNV infection in India. Moreover, out of 10 ISKNV-positive fish species, three species were reported positive to ISKNV for the first time in the world. Further, the in vitro experiment showed the growth of virus in Asian sea bass cell line, which is a natural host of ISKNV. Therefore, considering the lethal nature of megalocytiviruses to infect a vast range of species, proper biosecurity measures need to be taken to control these emerging pathogens.

Linking eggs and adults of Argulus spp. using mitochondrial DNA barcodes

We have created barcode library for common Argulus spp. infecting Carassius auratus, which could also be used to identify premature forms of Argulus spp. even by non-professionals. Infected C. auratus was examined and purchased from ornamental fish-trading centers and the adult life stage of Argulus spp. was identified and DNA barcoded. The eggs of Argulus spp. were collected using bottle implants. The collected eggs are barcoded and precisely identified by matching with the adult sequences. Four species of adult Argulus spp. were identified, namely Argulus japonicus, Argulus indicus, Argulus siamensis, and Argulus foliaceus. Precise identification of egg samples was done by two different analyses, namely (i) BLAST analysis and (ii) phylogenetic clustering of adults and eggs. All egg samples including the control were precisely identified by BLAST analysis and the results are consistent with phylogenetic clustering of adult and egg's DNA barcodes. In order to establish the DNA barcode technology for the identification of all Argulus spp and its premature forms, the development of full-fledged barcode library that includes all species of this genus is very important for the benefit of ornamental fish industries.