Abstract
1. Public aquaria globally display numerous threatened fish species captured from wild populations. Although aquaria usually aim to support sustainability and biodiversity conservation, the potential impacts of these harvests are rarely evaluated.
2. Sawfishes (family Pristidae) are one of the world’s most at-risk fish families and are highly valued by aquarium operators due to their potential to attract visitors. The Critically Endangered largetooth sawfish, Pristis pristis, is most commonly displayed species with more than 30 wild caught individuals exhibited globally.
3. In northern Australia, two public aquaria routinely release P. pristis back to the wild as they outgrow displays, intending to offset impacts of the original harvests. However, the conservation value of releases is unclear because the fate of released sawfish is unknown.
4. Using acoustic telemetry, the effects of captivity on P. pristis behaviour and survival were assessed by comparing rates of movement, patterns of habitat use, and survival between a group of aquarium released sawfish (n = 5) and a control group of wild sawfish (n = 5).
5. Aquarium sawfish had reduced rates of movement, were more sedentary, and occupied smaller activity spaces than wild sawfish; but diel activity and habitat use patterns were similar.
6. Mortality was high for both groups, with two aquarium sawfish surviving to the end of the monitoring period (391 days and 117 days respectively), and no wild sawfish surviving. The mean duration of survival for aquarium and wild sawfish was 157 and 58 days, respectively.
7. Rapid growth rates and the avoidance of a period of high natural mortality whilst in captivity may explain the longer survival times of aquarium sawfish. Thus, whilst captivity affects sawfish behaviour, lower mortality rates of aquarium sawfish indicates that releases may partially offset the impact of the original harvest. Further survival, behavioural, and reproductive data are required to investigate potential long-term ecological impacts.
8. Results suggest that, if Pristis pristis are to be used for public aquarium displays, the best conservation outcomes could be achieved by harvesting in the first year of life when natural mortality is highest. This should be followed by release into the freshwater reaches of the natal river where predation risk may be minimised. Size on release should be less than ~2800 mm total length to allow for migration from the river system as part of their natural life cycle.
2. Sawfishes (family Pristidae) are one of the world’s most at-risk fish families and are highly valued by aquarium operators due to their potential to attract visitors. The Critically Endangered largetooth sawfish, Pristis pristis, is most commonly displayed species with more than 30 wild caught individuals exhibited globally.
3. In northern Australia, two public aquaria routinely release P. pristis back to the wild as they outgrow displays, intending to offset impacts of the original harvests. However, the conservation value of releases is unclear because the fate of released sawfish is unknown.
4. Using acoustic telemetry, the effects of captivity on P. pristis behaviour and survival were assessed by comparing rates of movement, patterns of habitat use, and survival between a group of aquarium released sawfish (n = 5) and a control group of wild sawfish (n = 5).
5. Aquarium sawfish had reduced rates of movement, were more sedentary, and occupied smaller activity spaces than wild sawfish; but diel activity and habitat use patterns were similar.
6. Mortality was high for both groups, with two aquarium sawfish surviving to the end of the monitoring period (391 days and 117 days respectively), and no wild sawfish surviving. The mean duration of survival for aquarium and wild sawfish was 157 and 58 days, respectively.
7. Rapid growth rates and the avoidance of a period of high natural mortality whilst in captivity may explain the longer survival times of aquarium sawfish. Thus, whilst captivity affects sawfish behaviour, lower mortality rates of aquarium sawfish indicates that releases may partially offset the impact of the original harvest. Further survival, behavioural, and reproductive data are required to investigate potential long-term ecological impacts.
8. Results suggest that, if Pristis pristis are to be used for public aquarium displays, the best conservation outcomes could be achieved by harvesting in the first year of life when natural mortality is highest. This should be followed by release into the freshwater reaches of the natal river where predation risk may be minimised. Size on release should be less than ~2800 mm total length to allow for migration from the river system as part of their natural life cycle.
| Original language | English |
|---|---|
| Pages (from-to) | 2351-2369 |
| Number of pages | 19 |
| Journal | Aquatic Conservation: Marine and Freshwater Ecosystems |
| Volume | 30 |
| Issue number | 12 |
| Early online date | 23 Aug 2020 |
| DOIs | |
| Publication status | Published - Dec 2020 |
