Differing environmental drivers of settlement across the range of southern rock lobster (Jasus edwardsii) suggest resilience of the fishery to climate change

Abstract

Temporal and spatial trends in settlement of the southern rock lobster, Jasus edwardsii, were examined to identify the influence of environmental variables over different spatial scales. Settlement data were collected from 1994 to 2011 along the Southern Australian and New Zealand coasts. We identified common settlement trends at a regional scale (100–500 km): the magnitude of settlement at sites from South Australia (SA) and Victoria (VIC) were similar, but different to sites in Tasmania (TAS). In New Zealand, three spatial regions were identified: northern (NNZ), middle (MNZ) and southern regions (SNZ). Higher settlement in SA, VIC and MNZ occurred in years with higher rainfall and storms in spring and El Niño conditions. In TAS and SNZ, higher settlement occurred during La Niña conditions. These results suggest that settlement over regional scales is modulated by oceanic processes, but outcomes vary between regions. At a local scale, a higher wave period and wind relaxation were relatively more important than the sea surface temperature (SST) in SA and VIC. In TAS, the current velocity also influenced the strength of settlement. However, much of the local settlement variability was not explained by the models suggesting that settlement in J. edwardsii is a complex process where larval behaviour, biological factors and oceanographic processes interact over different scales. The apparently complex processes affecting settlement showed that environmental conditions that reduced settlement strength in one region of the fishery often increased settlement strength in other regions. This could provide resilience to climate change at the stock level.

Temporal genetic patterns of diversity and structure evidence chaotic genetic patchiness in a spiny lobster

“…These two distinct oceanic features created genetic patchiness along P. argus’ geographic range (Truelove et al., ). In the case of J. edwardsii , patterns of settlement abundance have also been attributed to oceanographic features that vary in strength and importance among regions (Hinojosa et al., ). An oceanographic model simulating larval transport of J. edwardsii suggested that there is a high degree of self‐recruitment in areas such as Cape Jaffa (Bruce et al., ).…”

“…This suggests that either the selective forces acting during early postsettlement of J. edwardsii differ across the geographic range of the species and from year to year, or that different loci are responding to the same selective pressure. Differences in selective pressures would be the most likely scenario given that climate‐ocean forces driving settlement in J. edwardsii are also variable across the species distribution (Hinojosa et al., ). As mentioned above, predation is the main source of mortality after settlement.…”

“…The southern rock lobster, Jasus edwardsii , represents a valuable fishery in Australia and New Zealand. It occupies a wide geographic range, approximately between 110–180°E and 30–50°S, and subpopulations are exposed to different temperature regimes along this latitudinal gradient (Hinojosa et al., ). Studies assessing population structure of J. edwardsii have distinguished large‐scale neutral and adaptive differences between populations in Australia and New Zealand (Morgan, Green, Murphy, & Strugnell, ; Thomas & Bell, ; Villacorta‐Rath et al., ).…”

“…High variability in year‐to‐year settlement abundance of J. edwardsii and the subsequent fluctuating commercial catch rates have been described and attributed not only to variation in adult reproductive output (Kennington, Melville‐Smith, & Berry, ), but to fluctuating environmental factors prior to settlement. Due to the wide geographic range of J. edwardsii , the strength of the environmental factors driving settlement abundance differs from region to region (Hinojosa et al., ). Although interannual variation in settlement abundance has been widely studied for J. edwardsii (Booth, ; Hinojosa et al., ; Linnane et al., ), no study to date has assessed whether year‐to‐year fluctuations are also observed in the genetic structure and diversity of pueruli and to what extent natural selection during early postsettlement could affect population structure.…”

“…Due to the wide geographic range of J. edwardsii , the strength of the environmental factors driving settlement abundance differs from region to region (Hinojosa et al., ). Although interannual variation in settlement abundance has been widely studied for J. edwardsii (Booth, ; Hinojosa et al., ; Linnane et al., ), no study to date has assessed whether year‐to‐year fluctuations are also observed in the genetic structure and diversity of pueruli and to what extent natural selection during early postsettlement could affect population structure.…”