potential threats have been identified, there are no obvious explanations to account for their decline. Few studies have specifically investigated effects of shipping on cephalopods, although the literature suggests that shipping noise can cause physical, physiological and behavioural changes in some organisms. The aims of this project were to: (1) undertake a desktop review of S. apama related research including population trends, threats, shipping impacts and management, (2) investigate the potential impacts of shipping on S. apama through field/laboratory experimentation and analysis, (3) incorporate outcomes from experimental research into an integrated model assessing population viability, and (4) discuss associated conservation and management implications for S. apama in USG. For the experimental component of the project, S. apama adults and eggs were collected from False Bay, Whyalla, South Australia and transported to SARDI Aquatic Sciences Centre at West Beach. Eggs were kept in flow-through polystyrene holding tanks and exposed to shipping noise and turbidity on either a twice weekly or fortnightly basis (i.e. relevant to shipping frequency), with appropriate control treatments. Hatching success of eggs and embryonic development (length and weight of hatchlings) were examined for each treatment. Adults were held in individual flow-through conical tanks then placed in a resting respirometer and, after a suitable acclimation period (4 to 6 h), were exposed to reef and shipping noise in random order for approx. 2 h. Oxygen consumption in the chamber was measured to provide an indication of potential stress. Shipping noise and turbidity had no significant effect on hatching success though hatchlings exposed to noise were 3-6% larger than the control group. Increased shipping frequency led to slightly increased hatching success and increased size of hatchlings, although this may relate to increased handling and movement of eggs in these treatments. Turbidity had no significant effect on hatching success or embryonic development. Given the lack of effect of these factors on hatching success it was not possible to incorporate these variables into a demographic model. Shipping noise also had no effect on the metabolic rate of adult S. apama. This research only investigated the effect of one component of sound, sound pressure. The experiments investigated lethal effects on egg development and sub-lethal effects on embryonic growth and adult metabolism, however shipping noise may
(noise and turbidity) on S. apama or the potential impact of saline discharge on adults. Table 1. Potential factors contributing to a decline in S. apama as summarised from Steer et al. () Additional threats listed by Halpern et al. () have been included as have other proposed and potential activities in USG. Factor Evidence Other comments Natural process No reports of S. in early 1980s, but present in 1986; historical newspaper reports suggest dead & dying cuttlefish in USG but not clear where they came from Species of cuttlefish not listed in newspaper reports Abiotic factors Climate change Sea level, sea temperature (see below), ocean acidification, ozone/UV – potential long-term effects possible but unlikely to have been significant changes in last 10-15 years Potential for longer term impacts; Prowse et al. (submitted) found decline in abundance in USG could not be attributed to climatic factors Temperature Average annual temperature showed no correlation with S. apama numbers. Lagged monthly temperature 0-12 months prior to peak spawning also did not affect abundance Potential for spikes or pulses in temperature to affect embryo survival
Other toxicant input Unknown No information available Hydrocarbon Range of invertebrates show no evidence of hydrocarbon residues Hydrocarbon contamination from Santos unlikely to impact S. apama Noise pollution No correlation between current shipping levels (2.4 vessels per and abundance or biomass of S. apama; unknown how shipping noise per se may impact S. apama Uncertain whether offshore shipping traffic may interrupt potential movement and migration pathways for S. apama entering and exiting Point Lowly spawning grounds Biotic influences Predators Dolphins, New Zealand fur seals, snapper, Australian salmon, yellowtail kingfish (see details below) Where possible, correlations made between S. apama abundance and annual catch of predators; spikes in abundance of predators may however occur, but difficult to know whether these impact abundance of S. apama Dolphins, Delphinus delphis and Tursiops aduncus Dolphins to feed on S. apama No estimates of local dolphin abundance, but anecdotal reports of an increase in abundance of resident dolphins NZ fur seals, Arctocephalus forsteri Unlikely to influence S. apama abundance; further research underway Relative abundance & foraging intensity of A. forsteri in USG unknown
investigating diet of A. forsteri Snapper, Chrysophrys auratus No correlation between annual commercial catch of C. auratus and abundance or biomass of S. apama Australian salmon, Arripis truttaceus No correlation between annual commercial catch of A. truttaceus and abundance or biomass of S. apama Yellowtail kingfish, Seriola lalandi No correlation between S. lalandi escapes and S. apama abundance or biomass Nearby S. lalandi aquaculture; No data on wild S. lalandi abundance Prey Western king prawns, blue crabs Diet of S. currently under investigation Western king prawns, Penaeus (Melicertus) latisulcatus No clear relations between annual estimates of commercial catch of P. latisulcatus and abundance or biomass of S. apama Blue crabs, Portunus armatus Inverse correlation between annual estimates of P. armatus CPUE and S. apama abundance and biomass Suggests that S. apama predation mediates blue crab abundance Species invasion No known species invasion in USG
little change in behaviour of S. apama observed whilst diving; likely to be minimal Aquaculture Nearby S. lalandi aquaculture (see above); effects unknown Other potential threats Coastal engineering (e.g. breakwalls) May provide additional habitat but dependent on structure Coastal development (e.g. Ports & dredging) Turbidity may impact adult breeding behaviour S. apama require visual cues for reproduction Benthic structures May provide additional habitat depending on orientation Ocean mining Possible impacts through noise Mining leases exist in SG waters Desalination plant See salinity; possibility for other pollutants & turbidity effects; unknown how saline discharge might affect migratory routes onto/off breeding aggregation Previous experiments conducted on eggs; current experiments underway examining salinity and temperature effects and their interaction Defence Depends on activities in water