Assessment tool shows 33 aquatic species worldwide pose 'very high risk' of invasion

A global risk-assessment tool shows 33 nonnative aquatic species worldwide pose a "very high risk" of becoming invasive in current and future climate conditions.

"These species readily establish, spread and have severe impacts across several regions of the world," said Jeff Hill, a UF/IFAS professor of fisheries and aquatics and a lead author on a new study that used the risk-assessment tool. "The threat posed by invasive species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems."

That's why Hill worked with scientists across the globe to develop the Aquatic Species Invasiveness Screening Kit.

Scientists, including Hill, used the kit to assess the risk of such invasions. Once established outside its native range, an invasive species can cause environmental, social or human health impacts, Hill said.

Here are a few invasive species and their potential impacts in Florida, as outlined by Hill:

• Redear Slider, Trachemys scripta elegans. This turtle breeds with the native turtle known as the Yellowbelly Slider.
• Cane Toad, Rhinella marina. This large toad consumes smaller amphibians and competes with natives for food. It also secretes toxins dangerous to pets and wildlife.
• Amazon Sailfin Catfish, Pterygoplichthys pardalis. This armed catfish digs burrows for spawning. In doing so, it exacerbates erosion in natural waters and in stormwater ponds.

Hill helped lead a newly published study in the journal Science of the Total Environment that shows the risks of invasion by hundreds of species in the six inhabited continents.

For the study, 195 scientists used the Aquatic Species Invasives Kit (AS-ISK) to examine 819 species.

Their goal is to inform policy makers, those making day-to-day management decisions and other stakeholders about global threats to aquatic ecosystems, said Hill, a faculty member at the UF/IFAS Tropical Aquaculture Laboratory in Ruskin. Agencies and businesses across the word use the decision-support tool to help sustain aquaculture, the aquarium trade and fisheries management by identifying potentially invasive species before they establish and cause negative effects.

AS-ISK uses a scoring system. The higher the score, the higher the risk of a species becoming invasive. To get the most out of the tool, scientists calculate a score to differentiate between medium and high risk—normally non-invasive vs. potentially invasive. Researchers studied risk thresholds for species in various climates. Those factors provide a basis for scientists to interpret invasion thresholds.

Though helpful, the risk assessments are not meant to be comprehensive, Hill said. Each screen consists of 49 questions for basic assessment and six more questions about climate change.

Through their analyses, researchers provided global thresholds so natural resource managers can now assign species as "low," "medium" or "high" risk under current and future climate conditions, Hill said.

If the assessment is "high-risk," responses are to determine which species:

• Require an immediate, rapid management action such as eradication or control to avoid or mitigate negative impacts.
• Need a full risk assessment.
• Meet criteria for additional regulation in vulnerable areas.

This risk-screening tool used in this study is a generalized version of the Fish Invasiveness Screening Kit developed by the UF/IFAS Tropical Aquaculture Laboratory and the Centre for Environment, Fisheries and Aquaculture Sciences. Researchers use it as an international tool for nonnative freshwater fish.