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Invasive species are often more able to rapidly and efficiently utilise resources than natives, and comparing per capita resource use at different resource densities among invaders and trophically analogous natives could allow for reliable predictions of invasiveness. In South Africa, invasion by the Mediterranean mussel Mytilus galloprovincialis has transformed wave-exposed shores, negatively affecting native mussel species. Currently, South Africa is experiencing a second mussel invasion with the recent detection of the South American Semimytilus algosus. We tested per capita uptake of an algal resource by invading M. galloprovincialis, S. algosus, and the native Aulacomya atra at different algal concentrations and temperatures, representing the west and south coasts of South Africa, to examine whether their per capita resource use could be a predictor of their spread and subsequent invasiveness. Regardless of temperature, M. galloprovincialis was the most efficient consumer, significantly reducing algal cells compared to the other species when the resource was presented in both low and high starting densities. Furthermore, these findings aligned with a greater biomass of M. galloprovincialis on the shore in comparison with the other species. Resource use by the new invader S. algosus was dependent on the density of resource and, although this species was efficient at low algal concentrations at cooler temperatures, this pattern broke down at higher algal densities. This was once more reflected in lower biomass in surveys of this species along the cool west coast. We therefore forecast that S. algosus will be become established along the south coast; however, we also predict that M. galloprovincialis will maintain dominance on these shores., Author(s): Mhairi E. Alexander [sup.1] [sup.4] , Robyn Adams [sup.1] , Jaimie T. A. Dick [sup.2] [sup.3] , Tamara B. Robinson [sup.1] Author Affiliations: (Aff1) grid.11956.3a, 000000012214904X, Department of Botany [...]

The global ornamental fish trade is a multibillion‐dollar industry, with legal trade estimated to be worth between $15 and 20 billion per annum. Although there is existing legislation concerning the improvement of fish welfare in aquaculture and research, there is little legislation surrounding the welfare of pet fish. The different phases of the ornamental fish trade, including curation, transportation, time spent at wholesalers/retailers and time spent in domestic/public aquaria, represent different welfare concerns. Within the animal welfare field there is increasing interest in improving welfare through the creation of operational welfare indicators (OWIs), where individual indicators are aggregated to assess animal welfare. OWIs can be morphological, behavioural, physiological, metabolic or abiotic in nature, with behaviour often considered as the foremost non‐invasive method of elucidating welfare in fish. Currently, while OWIs exist for food fish species, there are no OWIs for use within the ornamental fish trade. This review looks briefly at the stressors experienced by fish within the ornamental trade, and then used a systematic approach (keywords behavio* AND fish* AND welfare) to identify relevant publications investigating existing behavioural measures of welfare used for ornamental fish species. Finally, this review considers the potential development of OWIs for the ornamental trade. [ABSTRACT FROM AUTHOR]

Characterising interspecific interaction strengths, combined with population abundances of prey and their novel predators, is critical to develop predictive invasion ecology. This is especially true of aquatic invasive species, which can pose a significant threat to the structure and stability of the ecosystems to which they are introduced. Here, we investigated consumer-resource dynamics of two globally-established aquatic invasive species, European green crab (Carcinus maenas) and brown trout (Salmo trutta). We explored the mediating effect of prey density on predatory impact in these invaders relative to functionally analogous native rock crab (Cancer irroratus) and Atlantic salmon (Salmo salar), respectively, feeding on shared prey (Mytilus sp. and Tenebrio molitor, respectively). We subsequently combined feeding rates with each predator's regional abundance to forecast relative ecological impacts. All predators demonstrated potentially destabilising Type II functional responses towards prey, with native rock crab and invasive brown trout exhibiting greater per capita impacts relative to their trophic analogues. Functional Response Ratios (attack rates divided by handling times) were higher for both invasive species, reflecting greater overall per capita effects compared to natives. Impact projections that incorporated predator abundances with per capita effects predicted severe impacts by European green crabs. However, brown trout, despite possessing higher per capita effects than Atlantic salmon, are projected to have low impact owing to currently low abundances in the sampled watershed. Should brown trout density increase sixfold, we predict it would exert higher impact than Atlantic salmon. Such impact-forecasting metrics and methods are thus vital tools to assist in the determination of current and future adverse impacts associated with aquatic invasive species. [ABSTRACT FROM AUTHOR]