Can MPAs conserve fish on marine soft sediments?

Soft sediments make up a large proportion of the total area of the ocean under protection in marine protected areas (MPAs). It is widely considered that on relatively homogenous marine soft sediment habitats, fish are... [ view full abstract ]

Soft sediments make up a large proportion of the total area of the ocean under protection in marine protected areas (MPAs). It is widely considered that on relatively homogenous marine soft sediment habitats, fish are unlikely to show site attachment and therefore will not remain inside MPAs for long enough to be afforded protection. However, as there is no movement information for the majority of fish species found on these habitats, it is currently impossible to say whether MPAs really are an effective conservation measure for these species. The bluespotted flathead (Platycephalus caeruleopunctatus) is a commercially and recreationally exploited species found on sand in South East Australia. Prior to this study there was no published data on movement patterns. Here we aimed to quantify movement and habitat-use of bluespotted flathead to: (1) determine whether site attachment is shown, (2) identify migration or aggregation movements, (3) compare movement to current no-take MPA design. We used acoustic tags and 48 acoustic receivers within Jervis Bay MPA to assess movement. Forty-six bluespotted flathead were tagged within the MPA and tracked for over 600 days. Bluespotted flathead exhibited strong short-term site attachment, with 37 fish detected within an 81 ha no-take zone for at least 2 months. Fifty percent of tagged fish exhibited long-term site attachment and remained in the no-take zone for 300–618 days. Taken together these outcomes indicate that bluespotted flathead show considerable site attachment on marine soft sediments. Current MPA design may well be adequate to afford this species protection.