A project undertaken at La Trobe University, and supervised by Dr Lucille Chapuis.
Human-made noise in the ocean is known to have a negative effect on the physiology and survival of marine fishes, such as altering the behaviour by masking important acoustic stimuli or inducing avoidance responses, which can result in physiological stress and damage to the hearing system. Most research in this field has focused on adult bony fishes.
As yet, no studies have investigated the effects of noise on cartilaginous fishes (sharks, rays and chimaeras) although these animals are usually particularly vulnerable to the threats posed by humans, notably due to their slow reproduction. Many species of cartilaginous fishes lay eggs (oviparous reproduction), which attach to structures on the sea floor by tendrils for anchorage. Embryos develop over a period of a few months to years before hatching. Juveniles then typically seek out specific coastal areas as nursery habitats to avoid predation.
In other species, the females gestate the fertilised eggs internally and give birth to live young (ovoviviparous reproduction). Embryos develop over one to two years where only the strongest survive and hatch inside the uterus. In these early stages of development, the juveniles, or eggs (and subsequently the hatchlings) are directly exposed to local environmental conditions, including anthropogenic impacts, with no ability to move away.
This project aims to assess the effects of noise on these critical early life stages of cartilaginous fishes. It will complement our larger, long-term, objective to understand the role of sounds for these animals and their vulnerability to noise pollution. We will assess the soundscape of nursery sites of three species of cartilaginous fishes: the Port Jackson shark, Heterodontus portusjacksoni, the Australian ghost shark, Callorhinchus milii, and the Southern fiddler ray, Trygonorrhina dumerilii. We will identify the sources of human-made noise in the area and expose egg-cases and hatchlings to relevant noise from anthropogenic sources to monitor their development, physiology and behaviour.
This study will establish, for the first time, an overlooked but potentially severe threat to an important group of fishes. There is currently no information on the vulnerability of cartilaginous fishes to noise and therefore no reference to this group in current protocols for environmental impact assessments or recommendations from regulators. By providing the first evidence of potential impacts, we will initiate a needed move towards evidence-based information.