Month: June 2024

The North Atlantic right whale (NARW) has been officially recognized as an endangered species according to the Endangered Species Act since 1970 (NOAA Fisheries, 2024). With only 360 individuals remaining, 70 of which are reproductively active females, understanding their past and current challenges is crucial for a more hopeful future.

Baleen whales were commercially hunted from the 16^th to 19^th century for their valuable blubber and baleen plates. During the peak of whaling, it was quickly realized that the North Atlantic species not only possessed the thickest layer of blubber but also remained floating at the surface after being harpooned. These characteristics earned them the name right whale, as they were the “right whale” to hunt, and thus made them a primary target. By the 19^th century, their numbers had decreased to the point where they no longer played a significant role in the whaling industry. The International Whaling Commission acknowledged that NARWs were on the brink of extinction and committed to globally protect the species in 1946 (Greene & Pershing, 2004). However, despite decades of protection, why has the population failed to recover?

With the end of commercial whaling, there was hope that the population of the NARW would gradually recover however, the reproduction rate is unable to keep up with the rate of mortalities. In addition to vessel strikes and fishing gear entanglement being the primary causes of death, the inevitable crisis of climate change has also been discovered to be a major contributing factor.

Through previous years of tracking NARW migration patterns, scientists revealed that right whales travelled annually to the Bay of Fundy. The Bay holds great significance for this species, particularly due to its abundance of copepod plankton, which are known as the primary food source for the NARWs.

Now, with the Bay of Fundy being the fastest-warming ocean region across the globe, copepods are adapting in ways that are proving to be detrimental to the right whales (Bucci, Thomas, & Cetinić, 2020). A recent study confirmed this correlation by examining the size and lipid content of copepod populations. The study found that warmer water temperatures are negatively associated with copepod size, resulting in reduced energy intake (lipid) for North Atlantic right whales (Helenius et al., 2023). As a result, these whales are not only shortening their migration route to preserve their energy, but also fail to meet the energetic requirements needed to reproduce. If mom isn’t eating a substantially nutritious diet, is she really going to want to grow and birth a 2,000 lbs calf? I know I wouldn’t!

NARWs are therefore changing their migration trajectory in hopes of finding higher-quality food as temperatures are increasing. Previously, along the Western Atlantic coast, shipping lanes were diverged and speed limits were enforced during the seasons when right whales were likely to be present. But now that groups are travelling to colder waters with higher prey quality, these regions have yet to catch up and enforce these lifesaving regulations (NOAA Fisheries, 2024).

This discovery allows scientists to track and predict NARW populations based on prey quality and water temperatures. By doing so, it can hopefully limit the amount of vessel strikes and fishing gear entanglement by laying out regulations sooner rather than later. The earlier we can detect these changes, the closer we are to saving the right whale species. As a community, our job is to continue to educate and spread awareness on these occurring topics so that they will not only have a past but will be given a chance for a brighter future!

Written by:  Gaby Caird

References:

1. NOAA Fisheries. (2024). North Atlantic right whale. Retrieved June 4, 2024, from https://www.fisheries.noaa.gov/species/north-atlantic-right-whale
2. Greene, C.H., & Pershing, A.J. (2004). Climate and the conservation biology of North Atlantic right whales: the right whale at the wrong time? Ecology, 5(2), 29-45. https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/1540-9295%282004%29002%5B0029%3ACATCBO%5D2.0.CO%3B2
3. Bucci, A. F., Thomas, A. C., & Cetinić, I. (2020). Interannual variability in the thermal habitat of Alexandrium catenella in the Bay of Fundy and the implications of climate change. Frontiers in Marine Science, 7, Article 587990. https://www.frontiersin.org/articles/10.3389/fmars.2020.587990/full

4. Helenius, L. K., Head, E. J. H., Jekielek, P., Orphanides, C. D., Pepin, P., Perrin, G., Plourde, S., Ringuette, M., Runge, J. A., Walsh, H. J., & Johnson, C. L. (2023). Spatial variability in size and lipid content of the marine copepod Calanus finmarchicusacross the Northwest Atlantic continental shelves: implications for North Atlantic right whale prey quality. Journal of plankton research, 46(1), 25–40. https://doi.org/10.1093/plankt/fbad047
5. Knowlton, A. R., Hamilton, P. K., Marx, M. K., Pettis, H. M., & Kraus, S. D. (2012). Monitoring North Atlantic right whale Eubalaena glacialis entanglement rates: a 30 yr retrospective. Marine Ecology Progress Series, 466, 293–302. http://www.jstor.org/stable/24876125

What is the first think you think of when you hear the word “shark”?

Is it a bloodthirsty man eater? A huge underwater torpedo with thrashing jaws and sharp teeth? Or is it perhaps the iconic Jaws theme song? Many people who hear the word “shark” immediately think of the horrors portrayed through movies and tv shows regarding these insatiable eating machines. But what if I were to tell you they aren’t exactly correct? In regard to some species at least, these allegations couldn’t be farther from the truth, and instead can be rather detrimental to these species’ reputations.

One such species I am referring to here is the elusive basking shark. This species, despite its name, is actually a fish. And while all sharks do in fact fall under the fish category not all fish fall into the shark category. To be a shark one must have a number of characteristics which distinguishes them from other fish. One such characteristic consists of having a skeleton made out of cartilage rather than one made of bone.

Out of all the fish in the ocean the basking shark is considered to be the second largest fish species in the world, following close behind the magnificent whale shark. These species grow up to maximum lengths of 12 meters (40 feet), and 18 meters (60 feet) respectively, and surprisingly enough these species do not rely on eating other fish to reach these massive lengths.

But if they don’t rely on eating fish to grow this big, they must be eating something much bigger than fish, right?

(Gill Rakers)

(Baleen Plate)

WRONG! This species is actually a filter-feeder who relies on plankton (small and microscopic organisms who float/drift with the current) as its main food source, much like the baleen whales commonly found throughout the Bay of Fundy. However, dissimilarly to baleen whales, these basking sharks do not have baleen plates, rather they have massive gill slits that extend almost completely around  their heads which are lined with gill rakers. These gill rakers are bristle-like and grow to about 10cm in length, with each gill slit carrying between 1000-1300 rakers along each arch. Also referred to as planktivores, basking sharks actively select foraging areas with high densities of plankton, containing both phytoplankton (plants) and zooplankton (tiny animals). When feeding the basking shark will reduce its speed by approximately 24% and its gills and mouth expand massively, filtering approximately two thousand tons of sea water every hour!

But why slow down to eat? Wouldn’t they catch more food if they swam faster? The answer to that is somewhat complicated. While they would in theory catch more prey at higher speeds, they also risk expending very high amounts of energy. Basking sharks require a perfect balance. Swim too slow and they may not filter enough food to fulfil their metabolic needs, or swim too fast and risk wasting more energy than they gain from the prey they catch. This perfectly balanced speed is called optimal foraging speed, where they maximize food ingested with the lowest energetic cost.

But one question still remains. How do they grow so big by eating such small prey?

Let’s break it down into simple terms. In this scenario phytoplankton will contain 1000 units of energy. When the phytoplankton is eaten by zooplankton it loses some energy, so the zooplankton only gains 100 units of energy. The zooplankton is then eaten by a small fish who only gains 10 units of energy, and the predator who eats the fish only gains 1 unit of energy. This trend then continues on until it reaches the top carnivores.

So, in other words, the closer you eat to the bottom of the food chain the higher amounts of energy you will gain. This is why the basking shark is able to grow to such large lengths. Because they feed on phytoplankton and zooplankton, they are able to fulfil their metabolic needs and then, using the abundance of extra energy they have, they are then able to direct it towards other areas such as their growth.

Written by Jayde Rapp

References

Campana, S. E., Shelton, P. A., Simpson, M., & Lawson, J. (2008). Status of basking sharks in Atlantic     Canada. Fisheries and Oceans.

How do whale and basking sharks grow so big eating such small food?. Wildlife Online. (n.d.).             https://www.wildlifeonline.me.uk/questions/answer/how-do-whale-and-basking-sharks-   grow-so-big-eating-such-small-food

Matthews, L. H., & Parker, H. W. (1950, November). Notes on the anatomy and biology of the Basking      Shark (Cetorhinus maximus (Gunner)). In Proceedings of the Zoological Society of London (Vol. 120, No. 3, pp. 535-576). Oxford, UK: Blackwell Publishing Ltd.

Sims, D. W. (2000). Filter-feeding and cruising swimming speeds of basking sharks compared with  optimal models: they filter-feed slower than predicted for their size. Journal of Experimental     Marine Biology and Ecology, 249(1), 65-76.

Sims, D. W., & Quayle, V. A. (1998). Selective foraging behaviour of basking sharks on zooplankton in a   small-scale front. Nature, 393(6684), 460-464.