Anthropogenic impacts on green turtles Chelonia mydas in New Zealand

Abstract

Conservation strategies to sustain endangered green turtle Chelonia mydas populations must categorise and mitigate a range of anthropogenic threats. This study provides first insights into some of the adverse effects of anthropogenic activities on green turtles at a foraging area in New Zealand. Gross necropsies were conducted on 35 immature and sub-adult green turtles that were stranded in northern New Zealand between 2007 and 2013. Results revealed 54% (n = 19) of individuals exhibited human-related trauma, and 63% of these (n = 12) had ingested synthetic marine debris. The predominant plastic items ingested were soft plastics (e.g. single-use food packaging, plastic bags), and white, clear or translucent items. No correlation was observed between curved carapace length and the volume or number of synthetic debris items ingested. Propeller strike injuries were identified in 26% (n = 5) of turtles exhibiting human-related effects, while 10% (n = 2) had evidence of incidental capture in recreational fishing activities. Importantly, within New Zealand waters, anthropogenic effects predominantly associated with plastic ingestion are impacting the green turtle aggregation, and may be an important contributory factor to the stranding of immature and sub-adult green turtles in this region. Consequently, the threats identified in this study should be considered when developing population-specific conservation strategies.

Marine Debris in Green Sea Turtles along the Northern Coast of Taiwan

“…Plastic ropes includes mainly the fishing lines such as monofilaments rope, and synthetic 'soft bait' lures rope for wrap up bags, etc. They are the marine debris originate mainly from the fishing vessels [4,8,31].…”

“…Plastics are lightweight, strong, durable, and cheap, making them suitable materials for a wide range of products; they are ubiquitous on land, and make-up most of the marine litter worldwide [6,7]. Synthetic debris types include single-use plastics such as food packaging, fishing line and synthetic 'soft bait' lures [8]. Plastics are not biodegradable, but use in many shortlived disposable products, and have great dispersal capabilities, making them a severe global environmental threat to marine ecosystems [2,6,9].…”

Plastic Pollution and Small Juvenile Marine Turtles: A Potential Evolutionary Trap

“…Records of plastic ingestion (> 1 mm) by marine turtles have been reported in the Atlantic (Musick and Limpus, 1997;Witherington, 2002;Mascarenhas et al, 2004;Di Beneditto and Awabdi, 2014;Santos et al, 2016;Colferai et al, 2017;Pham et al, 2017;Rizzi et al, 2019;Eastman et al, 2020;Machovsky-Capuska et al, 2020;Rice et al, 2021), the Pacific (Wedemeyer-Strombel et al, 2015;Ng et al, 2016;Clukey et al, 2017a;Godoy and Stockin, 2018;Jung et al, 2018a), the Indian Ocean (Hoarau et al, 2014;Yaghmour et al, 2018) and the Mediterranean Sea (Tomas et al, 2002;Campani et al, 2013;Camedda et al, 2014;Matiddi et al, 2017;Domènech et al, 2019;Digka et al, 2020). Drivers behind marine debris ingestion have included visual selectivity (Schuyler et al, 2012;Fukuoka et al, 2016;Duncan et al, 2019a), odour (Pfaller et al, 2020), or failure of discrimination when mixed with normal dietary items (Di Beneditto and Awabdi, 2014).…”

Finding Crush: Environmental DNA Analysis as a Tool for Tracking the Green Sea Turtle Chelonia mydas in a Marine Estuary

“…Development of new assessment methods for sea turtles is becoming increasingly urgent given concern over how changing oceanographic conditions may shift their distribution and habitat use. Greater occurrence of sea turtles within urbanised environments can result in more interactions with humans and associated risks, including drowning from entanglement (National Oceanic and Atmospheric Administration Marine Debris Program, 2014; Godoy and Stockin, 2018), ship strikes (Hazel and Gyuris, 2006), and exposure to toxins .…”