I can hear you: the effects of shipping on the behavior of Arctic cod (Boreogadus saida)

By: Victor Bach Muñoz

 

When people think about noise in the ocean, they may think about negative effects on species that are known to be vocal in popular culture, like cetaceans (Ellison et al. 2012). However, whales and dolphins are not the only species affected by the increasingly abundant anthropogenic marine noises, as studies on fish have previously demonstrated (Simpson et al. 2016). Much of this marine noise comes from boat traffic, which quadrupled in only two decades at the beginning of the century, raising concerns among scientists about how marine communities may be affected (Tournadre 2014). However, until now, the Artic marine habitats had remained relatively spared by the this increase in shipping activities, mainly due to the Arctic’s sea ice cover. However, climate change has been severely affecting the Arctic sea ice extent during summer months, reducing it by 49% from the 1979 to 2000 baseline average in 2012 (Overland & Wang 2013). This phenomenon is now opening greater boat traffic opportunities through the Northwest Passages, including the Parry Channel (Figure 1).

Figure 1: Map of the Northwest Passage routes and location of Resolute Bay, Nunavut, Canada (Source: Ivanova et al. 2012)

In 2012, Ivanova et al. conducted a study in Resolute Bay, Canada, to find out if sound from ships was influencing the movement patterns of an important polar species: the Arctic cod (Boreogadus saida). The researchers recorded the sound produced by the different types of ships traveling through the bay and tagged 85 Arctic cods (Figure 2) with acoustic transmitters (although only 77 where ultimately used to obtain data). Acoustic receivers in the bay where then used to triangulate the position of the tagged fish as the experiment unfolded, resulting in 11.852 detections between the months of July and September. The movements of Arctic cods where then compared to several variables including ship noise but also marine mammal presence, daily dissolved oxygen, water temperature, salinity, wind speed and wind direction. The results showed that the fish were having a negative response to the noise produced by ships, relocating to other parts of the bay away from those. Furthermore, the potential behavioral changes for the species could have extended ramifications to the many polar inhabitants that depend on it, from seabirds and toothed whales to all Arctic indigenous people.

Figure 2: Two Arctic cods (Boreogadus saida), also known as polar or boreal cods (Photo by Wikifranki from the Creative Commons)

As our planet’s ecosystems keep being affected by climate change, mankind is likely going to look for ways to make the best out of a bad situation. However, while the retreat of Arctic sea ice may offer new possibilities for shipping through the Northwest Passages, it is important to consider the impact that those newly more abundant human activities could have on those relatively pristine environments. While we navigate the surface in look for progress, the underwater communities that provide food and life are listening to our uproar, and it may be just too loud for them.

 

Work cited:

Ellison, W. T., Southall, B. L., Clark, C. W., & Frankel, A. S. (2012). A new context‐based approach to assess marine mammal behavioral responses to anthropogenic sounds. Conservation Biology26(1), 21-28.

Ivanova, S. V., Kessel, S. T., Espinoza, M., McLean, M. F., O’Neill, C., Landry, J., … & Fisk, A. T. (2019) Shipping alters the movement and behavior of Arctic cod (Boreogadus saida), a keystone fish in Arctic marine ecosystems. Ecological Applications, e02050.

Overland, J. E., & Wang, M. (2013). When will the summer Arctic be nearly sea ice free?. Geophysical Research Letters40(10), 2097-2101.

Simpson, S. D., Radford, A. N., Nedelec, S. L., Ferrari, M. C., Chivers, D. P., McCormick, M. I., & Meekan, M. G. (2016). Anthropogenic noise increases fish mortality by predation. Nature communications7, 10544.

Tournadre, J. (2014). Anthropogenic pressure on the open ocean: The growth of ship traffic revealed by altimeter data analysis. Geophysical Research Letters41(22), 7924-7932.

Are Natural History Films Really Raising Environmental Awareness?

By: Delaney Reynolds, SRC intern.

Films have influenced the way people perceive certain topics for decades. We all know and love the Jaws theme song, but soon after the movie’s release, mass hysteria broke out and a negative stigma has been associated with sharks ever since. Here at Shark Research and Conservation we, of course, know these apex predators are nothing to fear, but rather a respectable species that can provide us with a lot of information regarding environmental vitality. Thankfully, many others recognize this as well and social media platforms have played a very large role in dissipating the adverse reputation sharks have obtained. With social media ruling the world we live in today, are natural films and documentaries doing as well of a job at educating about conservation issues? Researchers at the University College Cork and University College Dublin set to find out.

In 2016 the British Broadcasting Company (BBC) aired its wildly popular show Planet Earth 2 narrated by Sir David Attenborough. The show brought in over 12 million viewers (BBC News). By looking at the engagement on Twitter and Wikipedia between November 6th to December 11th, 2016 (when the show aired), a qualitative analysis was performed based on the show’s script, the animal species it mentioned, the screen time they each were given, and conservation themes. In total, 113 animal species were mentioned and classified as mammal, bird, reptile, amphibian, fish, and invertebrate (Fernandez-Bellon, Kane, 2019). It was also noted that each species was described in part based on their predator-prey interaction.

Figure 1: The proportion of taxonomic groups based on screen time and IUCN conservation status. The number of species is represented by circle size, colors represent the IUCN conservation categories, bars represent taxonomic groups and proportions, and changes in circle size represents differences in screen time (Source: Fernández‐Bellon et al. 2019).

Based on the qualitative analysis, it was found that mammals were overrepresented in the show, thus all other categories were underrepresented, and the screen time that was allocated to specific species based upon their IUCN categories did not discuss or reflect conservation priorities (Figure 1). As such, audience engagement was highest in response to the mammals on the show and animals with an IUCN “least concern” conservation status also dominated airtime.

Figure 2: Audience engagement for ten species that were featured in Planet Earth 2 from (a) Twitter and (b) Wikipedia. Twitter engagement was based on the number of times each species was mentioned under #PlanetEarth2 and Wikipedia engagement was based on the number of visits to each species’ specific page. Colors represent the IUCN conservation status, red shading in (b) represents the 6 weeks that Planet Earth 2 was aired, and the darker red band illustrates the specific episode each animal was highlighted in (Source: Fernández‐Bellon et al. 2019).

In total, 30,000 tweets were posted under #PlanetEarth2 during the broadcast of the show and it was evident that species screen time per episode had a significant impact on audience engagement. Only 6% of the entire script for the show was dedicated to conservation education, leading to 1% of tweets mentioned containing conservation themes (Figure 2a). Based on the Wikipedia analysis, 41% of the animal species highlighted in the show recorded a yearly peak in page visits during the episodes of their respective animal species and, again, screen time of animal species had a significant effect on engagement (Fernandez-Bellon, Kane, 2019). The more screen time an animal received, the more it was tweeted about or searched for.

Given the extreme success of nature films and documentaries, just like Planet Earth 2, they can be fantastic platforms to educate a large amount of people about different conservation and environmental issues. Unfortunately, Planet Earth 2 did not feature conservation themes nearly enough, but this study shows just how effective such a platform can be in informing an extensive audience and with environmental issues emerging as a key issue for our society, it will be crucial to include them. So, no, not all nature films are currently doing their job in raising environmental awareness

 

Works Cited:

Fernández‐Bellon, D, Kane, A. Natural history films raise species awareness—A big data approach. Conservation Letters. 2019;e12678. https://doi.org/10.1111/conl.12678

“Planet Earth II More Popular than X Factor with Young Viewers.” BBC News, BBC, 1 Dec. 2016, www.bbc.com/news/entertainment-arts-38170406.

 

Electronic monitoring in fisheries: Lessons from global experiences and future opportunities

By: Isabelle Geller, SRC intern

Marine life and the resources the oceans provide are not infinitely abundant. To protect the seas’ limited resources, protection and monitoring are of the utmost importance.

Prior to the 20th century, the impacts of large-scale fishing operations on the marine ecosystem were unknown and under-monitored. Today there is that technology that exists, such as Electronic Monitoring systems, which enable fisheries an easy way to adequately monitor their catch.

Electronic monitoring systems, or EM for short, consist of various sensors positioned on the vessel to remotely record fishing activity and catches – these include geographic positioning systems (GPS) and cameras, paired with computer hardware (Figure 1). The recordings taken are able to be replayed later to generate important catch information including species composition, numbers, volumes, and lengths (van Helmond et. al 2020). One of the advantages of the EM system is that it could eliminate the need for high cost “catch observing” personnel aboard fishing vessels.

Figure 1: Typical electronic monitoring system setup (van Helmond 2020).

A recent study found EM systems to have numerous advantages and disadvantages (Figure 2).

Three important disadvantages of the EM system include

  1. Possible data loss and the risk of system failure.
  2. Camera placement may be intrusive or blocked by dirt or vessel personnel.
  3. Low acceptance from the fishing industry because the system may represent governments’ mistrust of the fishers.

Figure 2: Analysis of the EM data collection compared with previous data collection methods (van Helmond 2020).

Despite the threats and disadvantages detailed above, according to the study the following three advantages greatly outweigh the disadvantages.

  1. In the long term the EM program is much more cost efficient than the current on-board observer program.
  2. Since recordings can be re-watched later to verify data, the EM system enables fisheries to document better fleet representations.
  3. Location and catch registration are made easier by the onboard GPS and ability to verify accurate bycatch.

The study found that EM on its can be used to fully document a fishery or in combination with current data collection techniques for management and compliance and or scientific data collection. The biggest challenge that proponents of EM systems face moving forward is the ability to rebrand their purpose as one of verifying fishers’ manual documentation of catch (for accurate data collection and fisheries management), rather than one of government intrusion based on mistrust.

 

 

Works cited

van Helmond, ATM, Mortensen, LO, Plet‐Hansen, KS, et al. Electronic monitoring in fisheries: Lessons from global experiences and future opportunities. Fish Fish. 2020; 21: 162– 189. https://doi.org/10.1111/faf.12425

A spatiotemporal long-term assessment on the ecological response of reef communities in a Caribbean marine protected area

By: Megan Ando, SRC intern.

Marine Protected Areas (MPAs) have played a large role in the maintenance and conservation of vital marine ecosystems and species, many of which are endangered due to anthropogenic and natural causes. They also provide an ideal setting in which to perform long-term monitoring studies in order to analyze trends in coral reef communities, which provide a vast amount of insight into an ecosystem’s resilience. A compiled study, carried out over the course of 11 years by Martínez-Rendis et al., set out to observe one of these MPAs in hopes of assessing both the spatial and temporal long-term trends of some of the coral reef community indicators, which can be essential when it comes to mitigating and adapting to the several consequences of ecological shifts (Ricart et al., 2018). Being carried out in Cozumel, Mexico, studies like this are vital due to the recently recorded rapid degradation of coral reefs that are proven to be so important for the well-being of our planet (Mora, Graham, & Nyström, 2016). There have only ever been a few studies carried out in the Caribbean that provide time sequences and indicators of these systems, so studies like this provide the scientific community, and the world, with a great array of knowledge concerning the resilience of such a natural protected area.

As previously mentioned, this study took place in Cozumel, Mexico along six different reefs, all within different “zones” contained in the Cozumel Reefs National Park (CRNP) (Figure 1). These zones vary in their restrictions regarding fishing, scuba-diving, cruise ships, and other tourist activities that attract so many people to this reef system from around the world. The sampling performed in this area was executed through the use of transects, along which coral species, fauna densities, and other important details about the surrounding area were all recorded. The aforementioned indicators were also taken note of, which included densities of fish species, densities of trophic groups, species richness for each trophic group, relative cover of all scleractinian coral, and the corresponding relative coverage of macroalgae. Each of these indicators were eventually used in order to identify fish trophic groups with trends pertaining to the CRNP coral reef ecosystem, each of which would then infer information about the overall resilience of the MPA for future ecological conservation implications (Martínez-Rendis et al 2019). Such trophic groups have been used in the past to describe how fishing pressures affect reef trophic dynamics (Darling & D’Agata, 2017). Statistical tests were performed with all of this data to conclude their results.

Overall, it was found that differences in fish species appeared to be associated with distributions of the dominant species over the reef system, being controlled ultimately by environmental dynamics (Díaz-Ruiz, Aguirre-León, & Arias-González, 1998). Also, the changes seen in the densities of the fish trophic groups were both temporal and spatial, suggesting that both natural effects, including storms and hurricanes, and anthropogenic events, meaning construction and coastal development, cause changes in the abundance of these reef communities. As far as coral cover, there appeared to be a direct relationship between coral cover and corresponding macroalgae cover (Figure 2). Such algae cover could be promoted by an increase in coastal sediment discharge or other cumulative anthropogenic effects, which has the potential to surround and kill healthy coral.

To conclude, this group drew key conclusions regarding ecological trends and relevant constructive information that can be used to restructure the MPA for its own benefit as well as the benefit of the natural reef systems and all living organisms that it supports. It provides motivation for the further exploration of proper management strategies that need to be in respect to the tourists as well as the marine organisms in order to better conserve this reef system for generations to come.

Figure 1: Map showing location of Cozumel off of the Mexican coastline, as well as the various reefs and zones being studied within the CRNP (Martínez-Rendis et al 2019).

 

Figure 2: Graphic visual showing the direct trends in relative cover of scleractinian coral (purple) versus macroalgae (green) within the CRNP (Martínez-Rendis et al 2019).

 

Works cited

Darling, E. S., & D’agata, S. (2017). Coral. Reefs: Fishing for Sustainability. Current Biology.

Díaz-Ruiz, S., Aguirre-León, A., & Arias-González, J. E. (1998). Habitat interdependence in coral reef ecosystems: A case study in a Mexican Caribbean reef. Aquatic Ecosystem Health & Management, 1, 387–397.

Martínez-Rendis, Abigail, et al. (2019). A spatio-temporal long-term assessment on the ecological response of reef communities in a caribbean marine protected area. Aquatic Conservation: Marine and Freshwater Ecosystems, 30, 2, 273–289.

Mora, C., Graham, N. A. J., & Nyström, M. (2016). Ecological limitations to the resilience of coral reefs. Coral Reefs, 35, 1271–1280.

Ricart, A. M., García, M., Weitzmann, B., Linares, C., Hereu, B., & Ballesteros, E. (2018). Long-term shifts in the north western Mediterranean coastal seascape: The habitat-forming seaweed Codium vermilara. Marine Pollution Bulletin, 127, 334–341.

Refugia under threat: Mass bleaching of coral assemblages in high‐latitude eastern Australia

By Victor Munoz, SRC MPS student

When hearing about the effects of climate change on coral reefs, most will likely think of damage from coral bleaching events (Goldberg & Wilkinson, 2004). Because bleaching has been associated with higher sea temperatures, coral reefs exposed to colder waters can sometimes be viewed as more resilient to rises in temperature (West & Salm, 2003). However, those reefs might be just as vulnerable to climate change, although in a different way to what we may think.

Figure 1. A coral colony (Photo by Daniel Hjalmarsson on Unsplash)

A recent study by researchers from the University of Queensland (Kim et al., 2019) has evaluated the performance of 8,000 coral colonies across 22 sites on the southeastern coast of Australia during the hot summer of 2016 (Figure 2). After taking several snapshots of the corals at each site, the scientists gave them a score depending on how bleached they were. They then compared the status of different coral species to environmental factors including the hottest months’ temperatures, the annual temperature fluctuation and the solar irradiance the corals were exposed to.

They found that overall, these environmental factors poorly explained the health of corals. Some species were very sensitive to changes in temperature, while others showed greater resistance to heat stress. Instead, it seems like those increased temperatures may significantly affect the diversity of corals in colder waters, with some hardy species becoming dominant over more “fragile” ones. This could have serious implications for the less resistant cold-water corals, as locations closer to the poles (where they could potentially grow) lack the environments to sustain them. The disappearance of those “fragile” corals could then lead to a reduction of the overall coral diversity, with potential repercussions on the complex functionality of the reef’s ecosystem as a hole.

Figure 2. The 22 sites included in the study, across Australia’s southeastern coast. (Source: Kim et al., 2019)

Popular discussions around climate-change tend to focus on the species that we may lose (Willis et al., 2008), but new appearances or dominance of other species in affected habitats has been just as much of a reality (Rahel & Olden, 2008). The different ways every ecosystems may be impacted by the effects of climate change still need to be studied in greater depth, but what should be understood is that no location is truly “safe” from its consequences and that changes in the environment will be witnessed from the equator all the way to the poles.

Work cited:

Goldberg, J., & Wilkinson, C. (2004). Global threats to coral reefs: coral bleaching, global climate change, disease, predator plagues and invasive species. Status of coral reefs of the world2004, 67-92.

Kim, S. W., Sampayo, E. M., Sommer, B., Sims, C. A., Gómez‐Cabrera, M. D. C., Dalton, S. J., … & Figueira, W. F. (2019). Refugia under threat: Mass bleaching of coral assemblages in high‐latitude eastern Australia. Global change biology. doi: 10.1111/gcb.14772

Rahel, F. J., & Olden, J. D. (2008). Assessing the effects of climate change on aquatic invasive species. Conservation biology22(3), 521-533.

West, J. M., & Salm, R. V. (2003). Resistance and resilience to coral bleaching: implications for coral reef conservation and management. Conservation Biology17(4), 956-967.

Willis, C. G., Ruhfel, B., Primack, R. B., Miller-Rushing, A. J., & Davis, C. C. (2008). Phylogenetic patterns of species loss in Thoreau’s woods are driven by climate change. Proceedings of the National Academy of Sciences105(44), 17029-17033.

Don’t Treat Your Marine Sediments Like Dirt

By Sander Elliot, SRC intern

Marine sediments are home to a surprisingly diverse ecosystem of global importance. Subseafloor Life and its Biogeological Impacts (D’Hondt et al., 2019) overviews this ecosystem and roles it plays. Marine sediments are often overlooked because they are removed from our daily lives. If one takes the time to look into these communities, they reveal themselves to be quite interesting. The very fact that life manages to survive in such a barren environment deprived of light and oxygen is fascinating on its own. However, they do more than survive – they thrive.

The article states that the total number of cells in marine sediments rivals that of those in terrestrial sediments as well as in the ocean as a whole. The cells in marine sediments tend to be necessarily smaller than their open ocean and terrestrial rivals, so the biomass of marine sediments is not close to that of soil or the ocean. Even so, that diversity of life in place that seems desolate is not to be taken lightly. These communities are also crucial to large scale biogeochemical cycles that have a huge effect on the planet as a whole. The article zeros in on five specific global effects of these communities.

Firstly, is the impact on the global redox budget. The ocean and atmosphere are oxidized by the burial of reducing material, and the marine sediment communities modulate this process, greatly affecting the redox state of the oceans. The exact extent of this affect is not entirely known, but figure 1 gives a broad outline of the various processes.

Figure 1. Various chemical processes in seafloor sediments that effect the global redox budget. (Source: D’Hondt et al. 2019)

The second outlined effect concerns the global sulfur cycle. This is also part of the redox budget, but the effects of the sulfur go beyond that. Sulfur is a vital to life, and marine sediments are a crucial step in the sulfur cycle. The third effect is on alkalinity and atmospheric CO2. The sulfuric reactions that effect the sulfur cycle also effect the alkalinity of the seawater. It turns out that the alkalinity of seawater is partially responsible for the partial pressure of CO2 in said water. The partial pressure determines how much CO2 is dissolved from the atmosphere into seawater. The carbon cycle is of great importance and interest in the midst of anthropogenic climate change. Figure 2 shows the sea surface gas exchange that is affected by the alkalinity of seawater. 

Figure 2. A simple carbon cycle diagram that shows the gas exchange between the ocean and atmosphere. (Source: Wikimedia Commons).

The fourth impact is on the global nitrogen cycle. Marine sediments are a sink for most of the fixed nitrogen in the ocean, so they are the reason that many ocean ecosystems are nitrogen limited. The final impact is on geological resources. Microbial communities have a great affect on marine resourses of economic interest, specifically hydrocarbons. These affects need to be studied further but are known to be present. Marine sediments play a broad and crucial role in the earth’s biochemical cycles. They are an evolutionary marvel and proof that we are intricately connected to even the most far removed places in the biosphere.

Works Cited

D’Hondt S, Pockalny R, Fulfer VM, Spivack AJ (2019) Subseafloor life and its biogeochemical impacts. Nat Commun 10:1–13. doi: 10.1038/s41467-019-11450-z

Pacific Heat Wave Reduces Nutritional Value of Pacific Sand Lance

By Olivia Schuitema, SRC intern

A marine heat wave known as “The Blob,” lasted from October 2013 to June 2016 in the North Pacific Ocean (von Biela, 2019). Heat waves can have detrimental impacts with both immediate and lasting effects on the marine environment. These warm patches can produce bottom-up disruptions in energy transfer (von Biela, 2019). “Bottom-up” refers to an ecological concept where changes in the lower energy levels in a food chain affect the upper levels of that food chain as well.

A pivotal species in the Prince William Sound ecosystem are the key forage fish the Pacific Sand Lance (Ammodytes personatus) (Abookire and Piatt 2005). Sand lance are indicator species (species that help infer conditions of a certain habitat) that have strong residency and make minimal migrations, tying them certain habitat conditions (von Biela et al., 2019). They have direct connections to species in the upper levels of pelagic food webs including sea birds, marine mammals and larger predatory fish, some of which have conservation status or are targeted for fisheries (von Biela, 2019). Changes in stocks of sea birds and marine mammals have been linked to shifts in abundance of forage fish stocks (Robards, 2002).

Figure 1. Varying total lengths (TL) of Sand Lance, Ammodytes personatus (Source: USGS.gov)

Evidence suggests that abundance and growth rates of sand lance are related with certain environmental conditions such as marine productivity and water temperature (von Biela et al., 2019). Researchers examined the nutritional condition of sand lance in Prince William Sound within the 5-year warming period of “The Blob.” Sand lance samples were collected in the field and measured for total length. Back in the laboratory, otoliths (inner ear structures in teleost fish that aid in balance and orientation) were extracted from fish samples, dried and examined under light to see growth rings (von Biela et al., 2019). Otolith layers are similar to tree rings; age of fish can be determined via counting the number rings. Otolith growth size is strongly correlated to somatic size within fish species (von Biela et al., 2019). Determining whole body energy required drying out fish samples, pressing the dried remains into a pellet and weighing the pellet (von Biela et al., 2019).

Figure 2. Otoliths with dark bands representing periods of slow growth during heat wave (left), and otoliths with more opaque regions representing fast growth after the heat wave subsided (right) (Source: von Biela 2019)

Past studies indicated that sand lance grew slowest and were least abundant in warmer areas compared to cooler areas (Robards et al. 2002). Results of this study support past findings; with the higher temperatures during the heat wave, there was a decrease in total length and a decline in whole body energy in sand lance samples (von Biela et al., 2019). This suggests that with warming temperatures, sand lance must expend higher metabolic energy in order to survive, resulting in smaller size and smaller energy stores. In this type of domino effect, the warming temperatures then resulted in lower chlorophyll levels and lower nutrient levels, further contributing to the smaller fish size. These results mean less energy moving up the trophic levels, affecting the health of entire marine food webs. Shifts in climate and environmental conditions could have harmful effects on key species of forage fish such as the sand lance (Abookire and Piatt 2005). This important study could be a predictive snapshot into our future as global temperatures continue to rise.

 

Works Cited

Abookire AA, Piatt JF. 2005. Oceanographic conditions structure forage fishes into lipid-rich and lipid-poor communities in lower Cook Inlet, Alaska, USA. Mar Ecol Prog Ser 287: 229−240

Robards MD, Rose GA, Piatt JF. 2002. Growth and abundance of Pacific sand lance, Ammodytes hexapterus, under differing oceanographic regimes. Environ Biol Fishes 64: 429−441

Von Biela, R. Vanessa, et al. 2019. Extreme reduction in nutritional value of a key forage fish during the Pacific marine heatwave of 2014−2016. Mar Ecol Prog Ser 613: 171-182

Foraging energetics and prey density requirements of western North Atlantic blue whales in the Estuary and Gulf of St. Lawrence, Canada

By Nicholas Martinez, SRC intern

Pelagic predators throughout the world’s oceans face the same challenge: foraging for food in an environment where much of their prey are available in clusters, centralized around specific areas of the ocean. For this reason, many pelagic predators have unique ways to find these limited resources, all the while adjusting these foraging techniques so as to maximize energy gained for every unit of energy expended.

In a world where oceanic ecosystems are facing rapid change, the need for more research and implemented protective measures is rising. Many marine animals have been documented as having shifted their foraging habits because of a rapid decline in available resources. These resources, which have supported countless generations of predators, are now facing serious threats to their population size. For this reason, studies of the foraging habits of large marine predators allows insight into the hunting grounds that still remain for these animals. Understanding how often these species forage for food allows scientists to determine the health of a specific population of that species. A 2019 paper from Guilpin and colleagues, “Foraging energetics and prey density requirements of western North Atlantic blue whales in the Estuary and Gulf of St. Lawrence, Canada”, focused on the foraging efficiency of the North Atlantic blue whale in a quickly changing oceanic environment.

 

Figure 1. The blue whale (Source: NOAA Photo Library/anim1754/Wikimedia Commons)

Foraging efficiency is a ratio that compares the rate of energy consumption to the rate at which energy is expelled so as to provide insight into an organism’s ability to store energy. Understanding a blue whale’s capacity to store energy is crucial because there is a direct correlation between the animal’s energy supply and its ability to reproduce. Using 10 depth-velocity tags attached to the whales, the scientists were able to monitor the foraging behaviors of blue whales in the St. Lawrence Estuary. While blue whales are the largest living organisms on the planet, their food supply consists small invertebrates called krill, which can be found in large populations throughout the study site. This food source exhibits spatial and temporal variations and thus requires a specialized foraging technique in order to maximize the whales net energy reserve.

 

Figure 2. “Predicted change in blue whale foraging effort with time of day in (a) feeding depth (m), (b) dive duration (s), (c) number of feeding dives, (d) number of lunges d−1, and (e) number of lunges h−1. Dark grey ribbons represent the 95% confidence intervals around the predicted response from generalized additive mixed models. Shaded areas are for nighttime (grey), dusk and dawn (light grey), and daytime (white). Points are data observations” (Source: Guilpin et al. 2019, p. 213)

Here, the researchers found that during the day, the tagged blue whales performed fewer but longer feeding dives than at other times of the day (Figure 1). This suggested that the blue whales invested in fewer but longer dives so as to maximize the amount of energy they could store by minimizing energy expenditure (Figure 2). In addition, the authors found that the whales were performing more lunges per dive (accelerating towards the surface, trapping any krill in their mouth as they momentarily breach), showing that even while the whales were not deep diving, they were still feeding.

 

Figure 3. “Relationship between energy expenditure during feeding dives for 3 blue whale sizes (22, 25, and 27 m length) and (a) dive duration (s) … (b) maximum dive depth (m) … and (c) number of lunges per dive” (Source: Guilpin et al. 2019, p. 214)

Although the whales were observed to feed throughout the day, this did not necessarily mean that they were consuming enough krill to achieve a neutral energetic balance. In fact, this study found that only 11.7 and 5.5% of Arctic and northern krill patches contained densities that could sustain a neutral energy balance for the blue whales. This could be due to a decline of krill populations via environmental impacts, and if so, poses a great threat to blue whale populations. This information emphasizes blue whales’ constant need to forage for high densities of krill in order to maintain neutral energy balance or maintain a healthy energy storage suitable for reproduction. The discoveries made in this paper may therefore help predict the effects of climate change on both predator/prey densities and may also offer insight on potential krill fisheries and how they may or may not affect blue whale populations.

Work cited

Guilpin M, Lesage V, McQuinn I, et al (2019) Foraging energetics and prey density requirements of western North Atlantic blue whales in the Estuary and Gulf of St. Lawrence, Canada. Mar Ecol Prog Ser 625:205–223. doi: 10.3354/meps13043

Preventing ecosystems from feeling clammy: what monitoring giant clam populations can tell us about human perseverance

By Maria Geoly, SRC Intern

Every aspect of our lives depends on the health of our natural resources. Clean water, nutrient rich soil, and access to timber are often considered humanity’s three most essential natural resources because they provide the four essential needs of living things: oxygen, water, food, and shelter. Often overlooked, however, is the crucial role that animals play in maintaining healthy resources. A healthy ecosystem is comprised of many different components (Figure 1), that work in a checks and balances system to maintain harmony.

Figure 1. A depiction of how different organisms contribute to the balance of natural systems. (Source: https://www.sciencelearn.org.nz/resources/143-marine-food-webs)

Populations and demographics of the species comprising an ecosystem can be considered in decision toward ecosystem and resource management. The human implications of these decisions, however, are not always considered in the same way. An example of this comes from the Tuamotu atolls of French Polynesia, presented in a study from Georget et al. (2019).

The Tuamotu atolls used to have some of the largest populations of giant clams (Tridacna maxima) on Earth (Figure 2). Over thirty years, researchers had monitored the number of giant clams in this area –the ocean floor was divided into many squares or “quadrants” and giant clam individuals were counted within random squares, to estimate the number of animals in that habitat.

Figure 2. Giant clams, Tridacna maxima. (Source: National Oceanic and Atmospheric Administration)

From 2005-2012, hundreds of giant clams started dying off very quickly due to unusual weather patterns. The drastic change in population was observed by the atolls’ residents, however the method used by researchers to monitor population did not. This methodology, known as “LIT-Q” testing, is an accurate way to measure abundant species, but as a species’ numbers decline, “BT” sampling methods, which use one very long but thin quadrant at a time, tend to be more precise.

As scientists realized their mistakes, they decided to try both methods at once, in old and new giant clam habitats, to see if their past data was incorrect. Computer simulations were used to make models of both data sets, and scientists found that each testing method gave different estimates for each site, with “BT” sampling being the most accurate.

This study is important because it recognizes the need for flexibility and reflexivity in scientific practice. In Tuamotu and other remote fisheries across the globe, fishing quotas are determined by the estimated population densities of a species. If the numbers are off, unsustainable policy could be written that may lead to overfishing, harming entire ecosystems and the people who rely upon them. As in the case of Tuamoto, scientists actively questioned if what they were doing was right and used creative problem solving to fix past mistakes. The revaluation of what once worked helped the area recognize that overfishing of giant clams was occurring, and fishing quotas have since changed to support the sustained health both the giant clams and of the reef systems supporting them.

Persevering through the daunting task of fixing such a big data mistake is hard, but the reward that comes with new understanding and solutions to large problems like overfishing is well worth the struggle. Tuamoto serves as a global example of why scientific methodology should often be questioned and reevaluated. The long-term benefits are ecologically worth it.

Work cited 

Georget S, Van Wynsberge S, Andréfouët S (2019) Understanding consequences of adaptive monitoring protocols on data consistency: application to the monitoring of giant clam densities impacted by massive mortalities in Tuamotu atolls, French Polynesia. ICES J Mar Sci 76:1062–1071. doi: 10.1093/icesjms/fsy189

Mapping the global network of fisheries science collaboration

By Julia Saltzman, SRC intern

Collaboration is something which we all learn about as children. We are taught to work together in teams, to share our toys, and that ideas are better when many individuals contribute to them. As science has become increasingly internationalized, scholars investigating the shifting spatial structure have posed questions to whether networks of research collaboration are actually expanding despite the argument that broad-based collaboration is crucial to solving the challenges ongoing with respect to fisheries (Syed, ní Aodha et al. 2019). The global marine catch is approaching its upper limit, the number of overfished populations and the indirect effects of fisheries indicate that fisheries management has failed to achieve any sort of sustainability. This failure is primarily due to the continued increase in harvest rates in response to global pressure for greater harvests and the inability to accurately model sustainable catch amounts. Nevertheless, fisheries provide the direct employment to about 200 million people and account for nearly 19% of the total human consumption of animal protein (Botsford, Castilla et al. 1997). Fisheries are a crucial resource, and the only way to promote comprehensive management is with collaboration on a global level.

Figure 1: The global marine catch is approaching its upper limit, the number of overfished populations and the indirect effects of fisheries indicate that fisheries management has failed to achieve any sort of sustainability.

With the imperativeness of this collaboration in mind scientists mapped and examined the landscape of scientific collaboration across fisheries science. The results were quite interesting, the collaboration has become more extensive and more intensive in various places. However, the fisheries science landscape is one where the centers of knowledge production and the collaboration across scientists is far more regional than global. The regional manner of collaboration in fisheries science is likely to limit the potential benefits of collaboration. Collaboration which is regionally limited in such a global field will have consequences such as preventing the innovation which is necessary to address the ongoing challenges within fisheries management. There are several different aspects of fisheries management which can be learned from this study. First and foremost, collaboration on a global level is crucial for sustainable fisheries management. This collaboration should manifest itself in several different ways whether it be direct collaboration between various fisheries, collaboration among scientists who work in different fisheries, and collaboration among governments and fisheries management organizations.

Figure 2: Collaboration is something which we all learn about as children. We are taught to work together in teams, to share our toys, and that ideas are better when many individuals contribute to them. As science has become increasingly internationalized, scholars investigating the shifting spatial structure have posed questions to whether networks of research collaboration are actually expanding despite the argument that broad-based collaboration is crucial to solving the challenges ongoing with respect to fisheries.

Works cited

Botsford, L. W., J. C. Castilla and C. H. Peterson (1997). “The Management of Fisheries and Marine Ecosystems.” Science 277(5325): 509.

Syed, S., L. ní Aodha, C. Scougal and M. Spruit (2019). “Mapping the global network of fisheries science collaboration.” Fish and Fisheries 20(5): 830-856.