Marine biodiversity disrupted by recreational fishing entanglements and discards in the Garden Route.

On the 30th June, members of the Strandloper Project set off down to their primary reef transect at Gericke’s Point to attempt a reef survey and to recover snagged recreational fishing tackle.

I use the term ‘attempt’ as the sea conditions were not ideal. A huge swell was running and and the sea temperature was a chilly 16°C.

Reef Clean Up and Survey Dives.

In the 18 months that the Strandloper Project has being conducting reef cleanup dives and surveys, our core focus has been on ghost fishing with an emphasis on fish deaths attributed to snagged fishing gear.

As we have expanded our survey sites and broadened our attention to other deaths caused by lost and discarded recreational fishing tackle we have recorded physical damage to reefs, entanglements of marine birds and discards by fishermen of ‘pest’ species.

This survey trip highlighted the occurrence of both entanglement and indiscriminate discards attributed to recreational fishing.

Sea Barbel Discard.

In the Garden Route, Sea Barbel are regularly discarded by shore fishermen.

No sooner than we had started walking on the beach to our regular transect than we found a dead Sea Barbel. Situated at the high water mark this had all the signs of a discard.

Sea Barbel are considered a nuisance fish by surf fisherman, a pest that steals their bait and are regularly discarded and left to die on the beach.

They are a species that invests a huge amount of energy into reproduction, the female producing 15 and 100 eggs, depending on her age, that are slightly larger than a marble. As the eggs are forming they fill up her entire abdomen and she is unable to eat for up to six weeks. She also uses up a huge amount of her own resource for the development of the eggs and is extremely hungry when she lays the eggs. She will feed on any bit of food available and is a prime target for ghost fishing.

Once the eggs are laid the male fertilizes them and then takes them into his mouth for an incubation period of about 2 months. During this period he is unable to eat. Once they hatch he may keep the young in his mouth for their protection.

The male is also hungry when he has finished rearing his young and will feed on whatever food is available.

Sea Barbel play a crucial role in marine ecological health, feeding on dead marine organisms, particularly after rough sea conditions and should be returned alive to the ocean when caught.

Suffice to say, this was another unnecessary death with a potential consequence on marine biodiversity.

Bird Entanglements in Mono-Filament.

The consequence of avian entanglement, a leg of a Little Egret with entangled mono filament.

On reaching our site for our dive entry, Lisa found the leg of a Little Egret with mono-filament wrapped around it.

This bird had obviously become entangled in the snagged fishing line while feeding on the exposed flats at low tide. Unable to fly away it had then drowned as the tide came in. A tragic waste with another consequence to the ecology.

Constant Accumulation of Snagged Fishing Gear.

We kitted up and headed into the sea to start our dive. The last time that we had conducted a survey dive was on the 2nd June when we collected no less than 98 sinkers and associated tackle from our transect of 100m.

While this count of snagged fishing tackle ranks as our highest recovery from one dive in 18 months, what makes it even more disturbing is the fact that our preceding dive had been a week earlier, on the 26th May, when we recovered just over 90 sinkers and associated tackle from the same transect. As on previous dives, from one particular rock we recovered 15 sinkers in one handful, close to 15%. A simple way to prevent this repeated loss and snagging is to avoid casting in that direction.

A summary of lost sinkers and weight pieces recovered from our 100m transect at Gericke’s Point in the 18 months from January 2018.

Unfortunately the large swell and rough sea conditions forced us to abort our dive early. We also suffered some equipment losses. A fin and a GoPro were lost while exiting, making it an expensive dive.

The Strandloper Project team sunning themselves to warm up after the dive.

After sunning ourselves to warm up, we made another disturbing find on our way back to the parking area.

Though we try to remain objective during our cleanups and research, it is impossible to not let some of our findings trigger an emotion. Today it was one of despair.

Shark Discard Impacts Populations.

Hidden behind a rock above the high water mark was a Spotted Gully Shark, recently discarded. It was a female, approximately 1.4m long. They are a species that feed on crustaceans, molluscs and small fish. They have no pronounced teeth, though their jaws have small sharp teeth like rough sandpaper. They have a large mouth and buccal cavity and feed by sucking prey in.

They are a gentle species of shark and true to their name, take shelter in gullies to escape rough sea conditions. One of my most memorable shark swims was with no less than 13 of them in a gully on the Otter Trail, an experience akin to being with a pack of Jack Russels settling down to sleep after a meal. Mostly docile with random bursts of energy till all of them settled down.

As the shark was fresh Dr Louw Claassens from the Knysna Basin Project conducted a dissection. The stomach was full, with two fish (an advanced digested possible trumpet fish and a recently ingested Black Tail) and lots of Rock Crab exoskeletons.
We also inspected her ovaries and discovered that they were full of ova near to maturity and almost ready for fertilization.

From the dissection we could ascertain that the shark had fed well on Cape Rock Crab, Blacktail and a possible Trumpet Fish. It also had well developed ova.

Spotted Gully Sharks have a remarkable gestation of nearly 2 years and give birth to between 6 and 12 pups at a time. They live to an age 21 years and only reach sexual maturity at about 14 years old. Roughly speaking a female only has the ability to produce between 18 and 36 pups in her reproductive life.

Last night, not only did an inconsiderate fisherman unnecessarily kill a shark, but he prevented a minimum of 18 Spotted Gully Sharks from entering the ecosystem over the next 7 years (from the size of this female she was about 14 to 15 years old).
Considering this species role in maintaining trophic cascades on a reef ecosystem the ultimate consequence extends beyond the death of one shark to include a potential decrease of species in the mid trophic level. This sort of discard has the potential to jeopardise the sustainability of target fish species in the future.

Finishing up we learnt a lot on the trip. Hopefully our research helps others adopt a more ethical approach to utilizing marine resources.
If you aren’t going to use it, return it to the ocean. That is the only way to fish for the future.

The Strandloper Project focuses on studying the impact of shore based recreational on reefs and marine biodiversity. During their survey dives they analyse fishing tackle accumalation rates, damage to reef ecology and the incidents of ghost fishing and entanglements.