Patterns and drivers of movement for a coastal benthopelagic fish, Pseudocaranx georgianus, on Australia\u2019s southeast coast

Ashley M Fowler,John Stewart,Rowan C Chick

doi:10.1038/s41598-018-34922-6

Abstract

Knowledge of connectivity and population structure is integral to the sustainable management of fished populations, yet such information is unavailable for many species over scales relevant to their exploitation. We examined broad-scale patterns and drivers of adult movement for a putatively mobile carangid (Pseudocaranx georgianus) on Australia’s southeast coast using an angler tag-recapture dataset. More than 6300 individuals were tagged and released across 1007 km of coastline, with anglers recapturing 157 (2.48%) individuals during a 14-year period. Median distance moved was 5 km and a substantial proportion of individuals (19%) were recaptured at their release location. Recapture latitude was also strongly predicted by release latitude (r2 = 0.87). However, a broad range of movements were observed (0–508 km), with 6% of individuals moving further than 100 km. Most individuals recaptured in areas now designated as Marine Protected Areas (MPAs) were originally released in the same area (79.2%). Larger body size, longer periods at liberty, and releases during Spring all positively influenced distance moved. Results support restricted movement over an intermediate scale, punctuated by occasional large movements. Our findings suggest adult movement of P. georgianus in southeastern Australia primarily occurs over smaller distances than the current spatial scale of management.

Highlights

Despite the importance for management, scales of connectivity remain unknown for most exploited marine fishes[1]
Pseudocaranx georgianus is a commercially- and recreationally-important species in southeastern Australia[21], yet management has operated without detailed knowledge of connectivity and population structure
Despite fast swimming ability and offshore benthopelagic behaviour, our results indicate that movement of adult P. georgianus is likely restricted over the scale of fisheries management in the region (~1000 km), with a median distance between tag and recapture locations under 10 km and a high proportion of recaptures occurring at release locations

Summary

Introduction

Despite the importance for management, scales of connectivity remain unknown for most exploited marine fishes[1]. Many exploited species have a highly-mobile adult stage, capable of moving 100s of km within a lifetime[10] Such movements may further complicate patterns of connectivity established during the larval stage and remain poorly understood for most species[11,12]. Knowledge of the patterns and extent of post-settlement movement is essential for a holistic understanding of connectivity for mobile species Such information is critical for informing and evaluating spatial management approaches like Marine-Protected Areas (MPAs)[13]. Commercial and recreational fishers catch more individuals of target species than independent researchers and often do so over much broader spatial and temporal scales than can be achieved within a typical research program. Recreational harvests are an order of magnitude smaller than commercial harvests in both countries, with estimates of ~27 t in southeastern Australia[26] and ~190 t in New Zealand[25]

Methods

Results

Conclusion