A Big First Step Towards Protecting a Small Giant Guitarfish

Knowing how animals use the landscape, when and what for, provides information to determine whether a species is in decline and can show ways to turn this around. Divya Karnad (FFN Award winner 2019) and her colleagues are the first to set a baseline population size for the smallest species of the giant guitarfish and found potential conservation management methods along the way.

The widenose guitarfish is a critically endangered species found along the coastal waters of India. They are an important prey species and play a vital role in the functioning of the local marine ecosystems. Widenose guitarfish use nearshore habitats for foraging, nursery and resting, but these areas are vulnerable to development, pollution and fisheries. Despite India’s position as a hotspot for the giant guitarfish, studies have shown that their populations have drastically declined, as the fishery sector has expanded in the past 50 years. While there are protective regulations in place, they are not successful as guitarfish are often victim of bycatch.

From coastline to research site
Divya and the team of researchers focused on the South Goa coast to study how widenose guitarfish use their habitat in this region, and if this changes with the seasons. They also wanted to determine the abundance of the species in this area, and how environmental and anthropogenic factors, such as tide and tourism, influence this. This not only provides a current insight into how the species is doing in the area, but also creates baseline data to inform species-specific conservation and fisheries management plans.

Counting fish one step at a time
Divya and the team surveyed 10 beaches for over 6 months. With three beaches in particular the study focussed on the potential impact of anthropogenic activity. They walked along the beach in shallow water, counting the guitarfish, and noting their size to determine their approximate age. Usually research depends on fisheries to get estimates about presence and abundance for marine life, but using this walking transect method proved to be successful.  

Nursery at Gabgibaga beach
The study showed an estimation of over 500 individuals across the 25 km coastline, spread across the different beaches. One beach in particular, called Galgibaga, has an estimated abundance of 200 individuals, including a lot of young individuals. This is the beach Divya and her team determine as a potential nursery site. Galgibaga is considered an ecologically sensitive area, and already has some form of protection against construction and development. Long-term research will need to be conducted to confirm this, but identification of nursery grounds is a research priority for guitarfish globally as they provide space for the species in vulnerable early life stages making it important for species survival.

Seasonal population peak
The study also showed higher abundance in November and December, which could mean that this is the pupping season. This is sort of surprising, as other studies on other guitarfish species show higher abundances in summer compared to winter months. Research covering a full year is necessary to determine how population numbers change throughout the seasons.

Protecting the coast at the right time
Knowledge about pupping seasons could enforce regulations for protecting the nursery site during this season. Long-term monitoring will also confirm how anthropogenic activity in the area affects the species. The researchers found that population number were lower at the beaches with more anthropogenic activity, but there were too many other factors that might influence this to really confirm it. More research is necessary to be able to determine the need for policy changes such as restricting benthic nets in specific seasons or live release to minimize the impact of bycatch

A baseline for hope
Divya’s study provides valuable insights into the lives of the critically endangered widenose guitarfish which will help guide conservation management and policy. Read the full article here.