Impact of wind stress anomalies on the seasonal pattern of southern rock lobster (Jasus edwardsii) settlement in South Australia

Abstract

Quantified estimates of southern rock lobster (Jasus edwardii) puerulus settlement have been undertaken in the Southern Zone fishery of South Australia since the early 1990s. An analysis of mean monthly puerulus settlement indices from 1995 to 2007 in three monitoring sites revealed a strong seasonal correlation (r > 0.94 between sites) in settlement patterns. Settlement was highest during the winter months of June, July and August with peak settlement in all sites occurring in July. A reduced secondary settlement occurred during February and March. Seasonal trends were correlated with monthly wind stress and direction data in order to investigate possible environmental drivers of settlement. Using monthly averages of wind stress, it was hypothesized that strong alongshore wind-stress anomalies (ASWSA) prior to peak settlement would influence puerulus indices. Maximum ASWSA over the December-May period prior to maximum settlement was therefore examined. The results showed significant correlations (P < 0.1, r = 0.51-0.90) between wind stress and puerulus settlement in all but one site. We suggest that storm events, in combination with onshore surface drift during the period of settlement, are the principal physical oceanographic mechanisms influencing settlement patterns within the Southern Zone rock lobster fishery of South Australia.

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

“…Monitoring of settlement in J. edwardsii on artificial collectors has been undertaken throughout their distribution range for 20–30 years and has been used as a predictor of future recruitment to fishable biomass in some regions (Gardner et al ., ; Booth and McKenzie, ; Linnane et al ., , ). Monitoring of settlement in other spiny lobster fisheries has enabled the identification of environmental signals affecting settlement (Caputi, ; but see de Lestang et al ., ) and the impact of changes in the size of the adult breeding population (e.g., Ehrhardt and Fitchett, ).…”

“…Data from regional monitoring of settlement in J. edwardsii and other spiny lobsters has previously been used to search for associations with a range of recorded environmental variables as an effective first step aimed at identifying the environmental processes that drive settlement variability. For example, discrete projects at smaller spatial scales or time series in both South Australia and New Zealand have found that wind stress, Ekman transport and storm events associated with El Niño events can be related to seasonality and pulses of settlement (Booth et al ., ; Linnane et al ., ). At other locations, environmental variables influencing fluctuations in settlement have proven to be more difficult to isolate (e.g., Hayakawa et al ., ; Bruce et al ., ).…”

The Achilles heel for spiny lobsters: the energetics of the non‐feeding post‐larval stage

“…Phyllosoma subsequently metamorphose to pueruli offshore (Phillips et al 2006a). Physical forcing by wind or tidal currents may also influence onshore migration (Jeffs et al 2005;Linnane et al 2010b). Active swimming is thought to play an important role in the migration of pueruli into coastal waters, with pueruli being capable of sustained swimming velocities of 15 cm s À1 (Calinski and Lyons 1983;Jeffs and Holland 2000).…”

Environmental factors influencing the recruitment and catch of tropical Panulirus lobsters in southern Java, Indonesia

“…These patterns suggest that fishers do respond to the increased monsoonal rains by increasing effort but that improved catchability must also be influencing the higher catches. Thus, local and regional climate and oceanography appear to influence both lobster recruitment (Linnane et al, 2010) and catchability.…”

“…Lobster recruitment has been shown to be enhanced by strong on-shore winds during the late puerulus stages (Caputi and Brown, 1993;Linnane et al, 2010;Feng et al, 2011). Strong onshore southeast trade winds are common in southern tropical latitudes during the dry season (June-October).…”