*

The stock structure of Hapuku in Australian waters is unknown. Hapuku stock status at the jurisdictional level is sustainable in WA, negligible in QLD and SA, and undefined in NSW and Commonwealth waters.

The stock structure of Hapuku throughout Australian waters is unknown. Life history characteristics similar to Bass Groper (Polyprion americanus) suggest mixing across broad geographic areas [Ball et al. 2000]. However, Beentjes and Francis [1999] inferred the likelihood of separate stocks within New Zealand based on tagging studies of Hapuku, despite recorded movements of up to about 1,400 km. Paul [2002] reported on the stock structure of Hapuku (and Bass Groper) in New Zealand, concluding that stock structure could not be described, and that there was insufficient data describing the life history characteristics to distinguish different stocks. Wakefield et al. [2010] described differences in aged-based demography and reproduction of Hapuku among regions of Western Australia, and likely pan-oceanic mixing of the broader Hapuku population (including Indian Ocean). No such investigations have been done on Hapuku throughout eastern and south-eastern Australian waters to develop our understanding of stock structure. It is likely Hapuku in eastern and south-eastern Australian waters constitute one or more stocks of a greater population and fisheries within this region access this stock or subset of stocks in support of their annual catches. Panmixia could be expected throughout the region, owing to the extended larval/juvenile phase (years) and large-scale genetic homogeneity of congener P. americanus which has similar life-history traits [Ball et al. 2000; Roberts 1996; Sedberry et al. 1999; Wakefield et al. 2010]. Evidence in support of a single biological stock, or stock structuring within broader Australian waters is limited.

Here, assessment of stock status is presented at the jurisdictional level—Commonwealth, Western Australia, Queensland, New South Wales and South Australia.

New South Wales

Hapuku are primarily caught as a by-product species in the Ocean Trap and Line (OTL) Fishery on dropline gear, where the target species is commonly Blue-eye Trevalla (Hyperoglyphe antartica), although the proportion of total catch from different gears is changing with the general decrease in catch through time. Since 1997–98, commercial catches of Hapuku have been reported separately from Bass Groper (P. americanus). The annual reported commercial catches of Hapuku have steadily declined since at least the early 2000s, with this trend also reflected in the associated effort series and is consistent with reduced numbers of active fishing businesses in the OTL Fishery harvesting Hapuku. Within at least the last decade (2012–13 to 2021–22) the total annual commercial catch of Hapuku reported in NSW has averaged < 1.5 t, and within in the last 5 years (2017-18 to 2021–22) the average commercial catch was 0.9 t. Together with information on the mean weight (7.6 kg) of Hapuku caught and retained in the OTL Fishery, from unpublished data from an observer survey [Macbeth and Gray 2016], the commercial fishery for Hapuku in NSW is responsible for the removal of an average of < 120 individual fish per year over the last 5 years. 

From 1998-99, standardised catch rates (kg.day^-1) from droplining and that of nominal catch rates from handlining have not shown a clear trend over the time series of data available, with variance associated with the annual estimates substantially larger since about 2009-10, associated with fewer reported fishing events [Chick and Fowler 2023].

Although NSW commercial catches are low, the impact of fishing on the Hapuku stock in NSW remains uncertain. Recreational catch is potentially substantial relative to more recent commercial catches. This is despite state-wide surveys of recreational fishing not reporting recreational catches, due primarily to the design of the surveys, with large-scale phone and diary surveys like those of Henry and Lyle [2003], West et al. [2015] and Murphy et al. [2022] underestimating catches from small specific fisheries like the offshore deep-water recreational fishery. However, it is likely that the recreational component of the total catch has increased through time, due in part to the technological improvements that facilitate angling in deep water. 

Together with the uncertainty in total fishing mortality, demographic characteristics of late maturity, slow growth in later life and extended longevity reported from other regions and congener species suggest that the NSW stock is vulnerable to exploitation [Sedberry et al. 1999; Peres and Haimovici 2004; Wakefield et al. 2010]. Demography also likely varies across the extent of the stock(s) structure, as reported for south-western Australian stocks [Wakefield et al. 2010] and the extent of stock connectivity could be complex given life-history characteristics and oceanography of the region e.g. south-east Australian stocks of Blue-eye Trevalla, [Williams et al. 2017]. Added to these stock and species-specific uncertainties are broader pressures placed on stocks from human induced environmental processes such as climate change (e.g. ocean temperature and pH changes), resulting in greater variability in population responses to all pressures including fishing but also changes that are also likely to impact on fishing activities [Fulton et al. 2020]. These uncertainties, together with fishing pressures, could precipitate localised depletions or demographic shifts in stocks. 

A review of indicators (weight-of-evidence) approach was used to assess the status of Hapuku in NSW. There are insufficient data available to support more quantitative stock assessment methods. Important knowledge gaps and areas of uncertainty for Hapuku assessment include (i) stock structure, biology and quantified levels of recreational catch, (ii) low and decreasing levels of commercial catch together with similar patterns in effort (days), and (iii) low and variable catches and effort between different commercial fishing gears and methods, which exacerbate uncertainty surrounding estimates of standardised and nominal catch rates and their use as a proxy for change in biomass, provide insufficient information with which to support a reliable determination of stock status for NSW [Chick and Fowler 2023]. 

On the basis of the evidence provided above, Hapuku in New South Wales is classified as an undefined stock.

Hapuku biology [Ball et al. 2000; Paxton et al. 1989; Wakefield et al. 2010]

Distribution of reported commercial catch of Hapuku

Commonwealth – Commercial (Management Methods/Catch). Data provided for the Commonwealth align with the Commonwealth Southern and Eastern Scalefish and Shark Fishery and the High Seas Fishery for the 2021–22 financial year.

Commonwealth – Recreational. The Australian Government does not manage recreational fishing in Commonwealth waters. Recreational fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters, under its management regulations. 

Commonwealth – Indigenous. The Australian Government does not manage non-commercial Indigenous fishing in Commonwealth waters, with the exception of the Torres Strait. In general, non-commercial Indigenous fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters.

Western Australia – Recreational (Management Methods). Recreational Fishing from Boat Licence is required for use of a powered boat to fish or to transport catch or fishing gear to or from a land-based fishing location.

Queensland – Indigenous (Management Methods). For more information see: https://www.daf.qld.gov.au/business-priorities/fisheries/traditional-fishing

Queensland – Commercial (Catch). Queensland commercial and charter data has been sourced from the commercial fisheries logbook program. Further information available through the Queensland Fisheries Summary Report: https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/data/queensland-fisheries-summary-report

Queensland – Recreational Fishing (Catch). Data with high uncertainty (Residual Error > 50 %) have been excluded and listed as unknown. More information available at: https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/monitoring-reporting/statewide-recreational-fishing-surveys   

New South Wales – Indigenous (Management Methods). - https://www.dpi.nsw.gov.au/fishing/aboriginal-fishing

Commercial catch of Hapuku - note confidential catch not shown

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