Throughout the summer, I have been researching the patterns of the Scalloped Hammerhead (Sphyrna lewini) in the waters of Cape May and Wildwood from this year compared to last year’s data. Last year the American and Atlantic Star only had one data entry on a Scalloped hammerhead sighting, meaning one sighting where the shark stayed at the surface of the water for over five minutes (Long enough to take data). This year we have had over nine sightings of Scalloped hammerheads. These recorded sightings do not include times where a shark was spotted and immediately fled into deeper water. With that information we would assume that the population of scalloped hammerheads must be increasing, but unfortunately that would be an incorrect assumption. Although we have seen more hammerheads in our area from last year to this year, that doesn’t mean the population is increasing. In fact it is decreasing. Scalloped hammerheads were even the first hammerhead shark species to get put onto the IUCN red list. First, I will go through the data collected:
Last year the first, and only sighting lasting over five minutes was collected the American Star was from August 10th 2014. It was an AM trip where the conditions were clear, no precipitation, at least seven miles of visibility, five to ten knots wind speed, cat paw sea height, and one to two feet swell height. The area the scalloped hammerhead was seen was in the Delaware Bay/ Cape May area. There was only one found there. It was seen swimming at the surface of the water and very close to the boat. The conditions didn’t vary too much in the year 2015. The data on a scalloped hammerhead sightings were all seen in July. All clear with no precipitation, visibility was always at least 5 miles, wind speeds were all from five to fifteen knots, sea and swell heights were consistent from cat paw to four feet. Each was seen in the same general area of Cape May, Delaware Bay, or Wildwood. Most were seen individually while there was one instance where it was seen in the same area as a pod of dolphins, and another was seen with a humpback whale. Water temperature averaged 74 degrees fahrenheit and the water depth varied from 26.4 feet to 44.4 feet. Most seen were small juveniles. All were seen just swimming at the surface. With all of this information I was able to figure out that due to their migratory patterns they are extremely consistent with when they are in the south Jersey area. Next, I will talk about their ecology and ranges.
Scalloped hammerheads are found in coastal warm temperate and tropical waters, which explains why we only have data during the July and August months. Their range can go from New York all the way down to almost the tip of South America. Scalloped hammerheads are the second largest hammerhead, second to the great hammerhead. They are different due to the shape of their head. Scalloped hammerheads have ridges making it look like a scallop shell. The scalloped look comes from three indentations on their head one of which is in the center and two more beside that which you can see in figure two. Although there can be large groups found together, which are called aggregates, they are primarily seen individually or in pairs even.
As said before, I had decided to do my research on Scalloped Hammerhead sharks due to the fact that our data had shown an increase in sightings and I was curious if the population of these sharks were increasing. After doing to the research on it, I have seen that the population is in fact not increasing but severely decreasing. I found many different sources on the subject and found that they are actually on the IUCN Red List classified as endangered. I continued the research with what could be causing this decrease in population and what is being done about it. First, I will state the threats towards Scalloped Hammerheads.
The biggest threats in our part of the ocean, North West Atlantic Ocean, is the same as in any other ocean. Although in other parts of the oceans it is a lot worse. As seen in the map below in Figure 3, there are very few areas where Scalloped hammerheads are more numerous than others and are not considered in danger, Cape May and Wildwood area being one of them. Although in our area they may be doing well, in almost all other parts of the world they are not.
Scalloped hammerheads are not only caught by accident, but also on purpose. They tend to be caught in fishing lines and nets which primarily catch large numbers of pups and juveniles who get stuck. When they travel in large groups they tend to be more vulnerable to capture. The other reason their population is decreasing is due to their fins being very valuable. They are continuously sought after due to their large dorsal fin size and its fin ray count. Scalloped hammerhead fins account for 4-5% of the fins found in Hong Kong where the largest shark fin trading center is found. Fins can cost from $50-$100 per pound. So what is being done about this?
The conservation actions for Scalloped hammerheads are not where they need to be for this species. In the U.S. the Scalloped hammerhead is a part of the Large Coastal Shark complex management unit. Unfortunately, there are no management actions in this plan that are specifically for the Scalloped hammerheads. IUCN has recommended to limit catches of these sharks and increase monitoring of incidental catches in commercial fisheries. Although most of the U.S. has made shark fin trading and selling illegal which is a step in the right direction. That can’t be said for most other countries in the world.
While it may be very hard to get people interested in this animal to try to help them, it is extremely important to the environment. If we don’t have hammerhead sharks, or any sharks for that matter, then there will no longer be a balance of species in the oceans. We will be taking out a key predator in the food chain and there will be dire consequences if that happens. The most important message to take out of this article is the understanding of how important all animals are in the balance of nature. It’s extremely important to have them within our oceans.
Victoria Reader, Intern at Cape May Whale Watch and Research Center