New Zealand is a host to a variety of shark species from well-known species such as the great white – Carcharodon carcharias and whale sharks – Rhincodon typus to deep-sea species like the smalltooth sandtiger – Odontaspis fero and goblin shark – Mitsukurina owstoni sharks.
Some species are encountered more than others, one such species is the school shark – Galeorhinus galeus which is one of New Zealand’s most commonly encountered inshore shark species. Known by many names e.g., Tope, Tupere, Grey boy, and sand shark, school shark’s can be mistaken for other shark species such as bronze whalers – Carcharhinus brachyurus. More school shark or tope photographs.
Ranging in size from 30cm to just under 2m, school sharks can be distinguished from other shark species by their long, pointed, translucent snout, body colouration (greyish above, white below), and notched tail (the notch is generally longer than the rest of the tail’s upper lobe). Juvenile school sharks also have black colouration on the tips of their dorsal fins and the tip of their tail.
Despite predominantly inhabiting the continental shelf and coastal areas around New Zealand’s main islands, school sharks can be found as far north as the Three Kings Islands, as far south as the Campbell Islands, and up to 400 nautical miles off northern New Zealand towards the Kermadec Islands. This species typically inhabits the seafloor and can reach depths greater than 600m. Although, they can inhabit different areas of the water column and have been observed to make regular vertical migrations between the ocean’s depths and near-surface waters.
Encounters with school sharks are more common in coastal waters during summer when this species comes inshore to breed and feed. Over winter, juvenile school sharks will remain in coastal waters, whereas larger individuals will generally migrate to offshore habitats. This is where school sharks are more likely to be captured in pelagic environments.
Like other shark species, school sharks have complex movements, which are dependent on the habitat preferences of the individual. Movements may consist of short migrations between nearby habitats or sometimes may require large-scale migrations to reach or even return to their preferred habitat.
From movement data, New Zealand school sharks have been observed to move between New Zealand’s main islands and even undertake trans-Tasman migrations up to 4940km long. Australian school sharks have also been observed to also make trans-Tasman migrations to New Zealand.
Unfortunately, like other shark species, school sharks are vulnerable to overfishing and habitat degradation due to being high-level predators, slow-growing, long-lived, and reliant on particular habitats (i.e., nurseries). As a result of these threats, many school shark populations worldwide have been overexploited, with some subsequently collapsing and still being classified as overfished. This has led the International Union for Conservation of Nature (IUCN), in 2020, to re-classify school sharks, globally, as critically endangered and the Convention on the Conservation of Migratory Species of Wild Animals (CMS) to add school sharks to CMS Appendix II.
Luckily, in New Zealand, school sharks are still relatively abundant in our inshore waters. However, we know little about which inshore habitats are important to school sharks, and how and when they use them. Such information is key to help improve the management of this species.
The Kaipara Harbour, located in northern New Zealand, is the largest harbour in the southern hemisphere. The harbour’s large size and a broad variety of habitats make it important to many species such as Snapper – Pagrus auratus and the spotted smoothhound (rig) – Mustelus lenticulatus.
During the summer, juvenile and mature, and pregnant female school sharks are observed in the Kaipara Harbour in high abundance. This suggests that this harbour may contain important school shark habitats, including a potential nursery for newborn sharks. Although, this is yet to be confirmed.
Within New Zealand, school sharks from various regions have been observed to migrate to areas along the upper west coast of the North Island, with some being recaptured just outside the Kaipara Harbour. This suggests that the Kaipara Harbour may be important to school sharks from around New Zealand.
In the face of increasing human impacts in the region and the knowledge gaps that remain about how school sharks use different habitats, the importance of the Kaipara Harbour to New Zealand school sharks requires urgent assessment. This is where the research conducted by PhD student Alex Burton comes in.
Alex’s research aims to document the spatial and seasonal abundance, demographic structure, movements, heavy metal accumulation, growth, and diet of school sharks in the Kaipara Harbour in order to aid with this assessment. This information will be critical to efforts to conserve and protect this species in New Zealand waters.
For the movement section of his research, Alex is focusing on identifying school shark movement patterns to establish the origins of school sharks found in the Kaipara Harbour, what areas of the harbour different life stages use, and where school sharks are migrating too, once they leave the harbour.
To do this, he is using two types of tags. The first is mini–Pop-up Archival Transmitting (mini-PAT) or satellite tags, which collect and transmit data on the movements of sharks over the course of one year via satellite. The second is plastic ‘spaghetti’ tags, which have been, and are currently being used to tag and track the movements and growth of various fish, shark, and ray species around New Zealand as part of tagging programs such as the Tindale Marine Research Charitable Trust’s (TMRCT) inshore tagging program.
To track the movement of spaghetti-tagged individuals, Alex is relying on the public and fishers to report recaptures of tagged school sharks through the TMRCT inshore tagging program.
If you catch a fish that has been tagged, please take note of the following and report it to the TMRCT:
Tag number, Date captured, Capture location, Capture depth, Overall length, and Sex.
If possible, please also re-release the fish as it will allow for its movement to be tracked further. If you also find a spaghetti or satellite tag floating freely in the water or on the beach, please collect them and report them.
Furthermore, you can start tagging fish yourself by signing up to the program via the website here: Tagger Registration Form
If you tag school sharks in the Kaipara Harbour, Alex will replace the tags that are deployed onto school sharks. Another way to help is by talking to other people about getting involved. The more the merrier!
By becoming a citizen scientist and getting involved with Alex’s project and the TMRCT tagging program, you will be contributing to the conservation and kaitiakitanga (guardianship) of this species in New Zealand.
If you would like to contact Alex about his project, you can contact him on 0224005009 or via email: firstname.lastname@example.org
For more information on the TMRCT inshore tagging program, visit Tindale Marine Research Charitable Trust or email email@example.com
This post was last modified on 17/06/2021 2:49 pm
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