DEEP dive into the Two Oceans Aquarium

June 25, 2018

The Dyer Island Conservation Trust Environmental Education Programme(DEEP) second and third year intake learners visited the Two Oceans Aquarium on Wednesday, 20 June, as part of their programme. The programme focuses on the marine ecosystem.

During the course of the year the children learn about protecting and conserving the marine environment, including marine animals and rocky shores ecosystem. The visit to the aquarium aimed at showing the learners some of the marine animals that are covered in their curriculum e.g. stingrays, crabs, different shark species, fish species, jellyfish and many other species.

These learners are on their three year journey of becoming ambassadors for the ocean. The trip was an eye opener for these young ambassadors as most of them haven’t been out of Gansbaai. Seeing the big city was an amazing thing for the kids. They learned about movement of smaller animals through microscopes, which made them see the world in a different way. They asked the aquarium staff lots of questions about the marine life. Watching the feeding of stingrays was a highlight for them.

They learned about social stuff as well, using escalators, fork and knife, having the privilege to sit in a restaurant and order food of their choice. This wouldn’t have been possible if it wasn’t for South African National Lotteries who sponsored the outing and Wilfred Chivell for extra spoils and treats. Thank you to Marine Dynamics and  the International Marine Volunteers who assisted with the children.

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June 08, 2018

The Dyer Island Conservation Trust (DICT) officially launched the Fishing Line Recovery and Recycling Program along the Gansbaai shoreline in 2010. This innovative project of strategically placed unique fishing line bins aims to reduce the severe environmental damage caused by discarded fishing line on our coastline. “Our marine animal rescue team has seen some of the worst injuries on seabirds, seals and sharks caused from discarded fishing line. We have to date collected probably over 5000kms of fishing line. The fishing line bin helps create public awareness about the negative impacts that fishing line debris has on marine life, water quality, and human welfare. We place bins at our local beaches and popular fishing spots encouraging anglers and beach walkers to dispose of their used fishing line. We hope to reduce the amount of fishing line entering the marine environment, as well as to increase the amount of fishing line being recycled. We also conduct regular beach clean-ups. We have strong partnerships with organisations that help the reach and management of this project,” says Trust CEO Wilfred Chivell.

The first twenty bins were placed in partnership with Overstrand Municipality in the Gansbaai area. Since then bins have been placed at various locations around the country including alongside Blue Flag beaches and is proving to be an icon for marine pollution. Since 2011, DPI Plastics has been providing material for these bins. This dedicated and critical sponsorship was arranged by John Kieser of Plastics ǀ SA.
“Monofilament fishing line is non-biodegradable and can last for hundred of years in the marine environment where it entangles wildlife, is mistakenly ingested by birds and animals, resulting in injury or death, and is also hazardous to boaters and swimmers,” says Anthea Paulsen of DPI Plastics. “DPI Plastics would like to enlarge our eco footprint and be seen as eco leaders in our industry. We look forward to the continued reach of the fishing line bin project. It can grow so much further, not only along the coastline but inland for rivers and dams where the same problems exist."

Kieser is also responsible for organising interested organisations in South Africa to take part in the International Coastal Clean Up Day that happens every September. Kieser provides all bags, gloves and data cards for this annual event as well as all clean ups that take place throughout the year. “It is important that we collate the data forming an accurate picture of marine pollution and its sources in South Africa, so we can assess and advise plastic manufacturers where required. Product design can be revised minimising waste issues. The fishing line bin has been well received along the coast and a roadshow is planned for 2019,” says Kieser.

The team got together in Gansbaai on World Oceans Day, 8th June. After enjoying a whale trip with Dyer Island Cruises that reminded all of the marine world that needs protection, some fishing line bins were built with the Trust’s environmental education group. A bin was strategically placed in Stanford’s Cove in the De Kelders in an area commonly used by fishermen.

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Laser Photogrammetry – a non-invasive tool to yield key biological information from Sharks

June 04, 2018

The latest Marine Dynamics evening started on a positive note with Dyer Island Conservation Trust Environment Educational Programme, better know as the DEEP Blue ambassadors, opening with a short presentation on what this programme means for their education and personal development. The youngest future DEEP ambassador, Munashe Mudenge, just 6 years old introduced the rest of the team with ease. The group thanked their sponsors and Pinkey Ngewu, the educator of the Dyer Island Conservation Trust.

The Great White House management and staff recently took to using their singing talent to start a choir. They have been practicing under the expertise of musician Anza Naude for the last three weeks. This talented team entertained everyone with Margaret Singama – Lady Africa’s: Mama Thembu’s Wedding.

This month’s guest speaker was Marine Dynamics Guiding Biologist Toby Rogers, presenting on his research concerning sharks and laser photogrammetry.

Toby Rogers studied at UK based, Bangor University, where he graduated with a Master’s Degree in Marine Biology in 2016. Toby is the Academic lead of the skills-based Science Internship with the companies’ new venture, Marine Dynamics Academy.

Photogrammetry in simple terms is using still images to collect measurements of free-swimming animals. Non-invasive techniques are strived for in marine biology and the motivation behind Toby’s research was to pinpoint a technique that allows researchers to yield core biological metrics namely, size, sex and stage of sexual maturity, from sharks without having to touch the animals. These core biological metrics can then be used for management authorities when they are implementing conservation policy. Using lasers and cameras to capture measurement data from sharks provides an alternative to catching sharks.

The lasers point onto the flank of the shark, and because the distance between the two lasers is known (10cm) you can use image analysis software to scale your images and collect accurate measurements. However, it doesn’t appear to be as simple as it first might seem. It is not possible to use the software to measure from the tip of the snout to the tip of the caudal, due to the swimming behaviour of the shark. Therefore, you need to find a measurement proxy to try and predict the total length of the shark.

Typically, researchers will use a fixed point on the animal, usually the dorsal fin area. 101 catsharks (Shark Picture) that were caught as a result of by catch were used to gather detailed measurements of every body part (shark sketch), as well as identifying the sex and stage of reproductive maturity for each animal. This would then be useful for building models to predict these metrics from free swimming sharks.

To gather information about Total Length (TL), linear equations were calculated between three dorsal fin measurements and TL from the dead shark database. The strongest predictor of TL turned out to be the dorsal fin base length. Dorsal fin measurements can then be collected by using your cameras. Enter your measurement into the linear equation and your predicted TL will be produced. Since the researchers had live sharks in the tanks they were able to validate their predictions by comparing to the known total length of each shark. Results were shown to be very accurate and precise, which allowed the researchers confidence to collect finer scale measurements from the sharks in the tanks.

Laser photogrammetry has previously been used to measure whale sharks, white sharks and even Manta Rays. Therefore, they have provided further support that the technique is accurate to gather TL information. But the researchers also wanted to gain information about the sex and stage of reproductive. With sharks generally, you can determine males from females by looking for claspers where presence is male, and absence is female. However, with some juvenile male shark species, or even some of the more cryptic species it may not be as obvious. Identifying the level of reproductive maturity is a very difficult process. The team looked at using the analogy that different body parts grow at different rates during your life and applied this to the catsharks. By calculating ratios between different body parts, you can start to detect slight changes between males and females as well as mature and immature sharks.

A statistical test called Random Forest Classification Modelling, allows you to pinpoint the most important ratios that discriminate between male and females, and mature and immature individuals. To test for the accuracy of this, the measurements highlighted by the Random Forest Models were collected from the live animals in the tanks using the lasers and the camera. Ratios were calculated and applied to the model to predict the maturity level of the male sharks in the tanks. Since the team knew the maturity stage of each male in the tank, they were able to validate the model predictions. The models were able to correctly classify 79% of the immature males, and 100% of the mature males. Very good results indeed!

Next steps involve researchers to examine and determine whether the growth ratio technique will also work for other species of shark around the world and investigating the use of different camera arrays.

Thank you to all our guests supporting our Marine Evenings. We look forward to welcoming you to our next event.

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