18 June 2022. We are happy to report that our genomic silverside experiment has progressed from "Can we really pull this off?" to "We think we just might" over the past weeks. The silverside larvae of these different crosses show stunning size variability, between populations and temperatures. We already obtained two early life mortality estimates and lots of genetic material, including a full set of crosses reared at 26C and ad libitum food, reaching 20 mm in roughly 4 weeks post hatch. Fingers crossed for the rest of the rearing time.
A potential ripple effect from carbon in the atmosphere could have severe impacts throughout the ocean ecosystem
By Elaina Hancock. Reposted from UConn Today, 7 April 2022
When carbon is emitted into the atmosphere, about a quarter of it is absorbed by the earth’s oceans. As the oceans serve as a massive ‘sink’ for carbon, there are changes to the water’s pH – a measure of how acidic or basic water is. As oceans absorb carbon, their water becomes more acidic, a process called ocean acidification (OA). For years, researchers have worked to understand what effect this could have on marine life.
While most research so far shows that fish are fairly resilient to OA, new research from UConn, the University of Washington, the National Oceanic and Atmospheric Administration (NOAA), and Southern Connecticut State University, shows that an important forage fish for the Northwest Atlantic called sand lance is very sensitive to OA, and that this could have considerable ecosystem impacts by 2100. The team’s findings have just been published in Marine Ecology Progress Series 687.
Sand lance spawn in the winter months in offshore environments that tend to have stable, low levels of CO2, explains UConn Department of Marine Sciences researcher and lead author Hannes Baumann.
“Marine organisms are not living in a uniform ocean,” Baumann says. “In near shore environments, large CO2 fluctuations between day and night and between seasons are the norm, and the fish and other organisms are adapted to this variability. When we stumbled upon sand lances we suspected they are different. We thought that a fish that lives in a more open-ocean offshore environment might be more sensitive than the near-shore fish because there’s just much less variability.”
The project was a collaboration with physical oceanographers, including Assistant Professor of Marine Sciences Samantha Siedlecki and Michael Alexander from NOAA’s Physical Sciences Laboratory in Boulder, Colorado, who modeled CO2 levels in 2050 and 2100 for a specific part of the Gulf of Maine where sand lance spawn. Then Baumann and his team reared sand lance embryos in the lab under experimentally higher CO2 levels matching the projected levels.
There are instances of direct fish mortality as result of elevated CO2, but they are rare, says Baumann. However, sand lance embryos proved to be exceptionally sensitive, and fewer embryos hatched under future oceanic CO2 conditions. The researchers repeated the experiments three more times to avoid jumping to conclusions but each time they observed the same result.
“We found that embryo survival-to-hatch decreased sharply with increasing CO2 levels in the water, concluding that this is one of the most CO2-sensitive fish species studied thus far,” Baumann says.
Sand lances are surely one of the most important forage fish here on the Northwest Atlantic shelf… The humpback whales, sharks, tuna, cod, shearwaters, terns — you name it — they are all relying on sand lance.
With this interdisciplinary approach combining model forecasts and serial experimentation the researchers arrived at a picture that is much more specific.
“We consequently applied principles of serial experimentation, which is a most timely and important topic in ocean acidification research right now,” Baumann says. “Because our findings are backed up by repeated independent evidence, they are more robust than many published ocean acidification studies to date.”
In addition to preventing many sand lance embryos from developing normally, the researchers document a second negative, and novel, response to elevated CO2. Higher CO2 levels appear to make it harder for embryos to hatch.
Baumann explains the lowered pH likely renders enzymes needed for successful hatching less effective, leaving the embryos unable to break through their eggshell (chorion) to hatch.
The results show that by 2100, due to acidification, sand lance hatching success could be reduced to 71% of today’s levels. Since sand lance are such a critical component of the food web of the Northwest Atlantic, this marked decrease in sand lance would have profound impacts throughout the ecosystem.
“Sand lances are surely one of the most important forage fish here on the Northwest Atlantic shelf,” Baumann says. “Their range spans from the Mid Atlantic Bight all the way to Greenland. Where we studied them, on Stellwagen Bank, they are called the backbone of the ecosystem. The humpback whales, sharks, tuna, cod, shearwaters, terns — you name it — they are all relying on sand lance, and if sand lance productivity goes down, we will see ripple effects to all these higher trophic animals. Even though we humans don’t fish for sand lance, we need to take care of the species because it has such a huge effect on everything else.”
Baumann says this study supports the hypothesis that offshore, high latitude marine organisms like the sand lance may be among the most vulnerable to OA. As a result, these organisms and food webs will likely be impacted first and soon, and we must act now.
Previous research has focused on opportunistically chosen species when testing their sensitivity for ocean acidification, says Baumann, but this should change.
“We need strategic thinking about what species we are testing next, because we cannot test every marine fish species, that’s an impossible task. We should concentrate on fish species that are likely the most vulnerable, and therefore the ones that are probably being affected first and this research makes a compelling argument that those are the fish species at higher latitudes and in more offshore than nearshore environments.”
- Baumann, H., Jones, L.F.*, Murray, C.S., Siedlecki, S.A., Alexander, M., and Cross, E.L. (2022)
Impaired hatching exacerbates the high CO2 sensitivity of embryonic sand lance, Ammodytes dubius
Marine Ecology Progress Series 687:147-162
21 March 2022. Today, Baumann lab graduate student Kelli Mosca presented her Masters thesis entitled "Atlantic sturgeon (Acipenser oxyrinchus) Growth and Habitat Use in the Connecticut River and Long Island Sound". She did a marvelous job summarizing the multifaceted findings on age and growth of Atlantic sturgeon in the eastern Long Island Sound and the Connecticut River, their movement patterns based on analyses of acoustic telemetry data, while evaluating the evidence for indications that Atlantic sturgeon may utilize the Connecticut River again for spawning.
Kelli was an inspirational and cherished member of the Baumann lab, who literally mastered the challenges of being a 'whole-pandemic' Master student. Her dedication and continued work for CTDEEP were awarded by an offer for a CTDEEP Fishery Biologist I position, which she has wholeheartedly accepted. Congratulations Kelli, and all the best for the next steps in your career!
The UConn Department of Marine Sciences
Presents a Master’s Thesis Presentation by
B.S., University of New Haven, 2017
12:00 p.m., Monday, March 21, 2022
Lowell Weicker Building, Seminar Room 103 or Via WebEx
Atlantic sturgeon (Acipenser oxyrinchus) Growth and Habitat Use in the Connecticut River and Long Island Sound
Atlantic sturgeon (ATS, Acipenser oxyrinchus) are long-lived, anadromous, and endangered fish with a wide geographical distribution along the east coast of North America. Historically known to spawn in numerous rivers, many spawning runs ended due to intense fishing pressure and habitat obstruction in the 19th and 20th centuries. This was thought to be true for the longest river in the US Northeast, the Connecticut River, until pre-migratory ATS juveniles appeared in the river in 2014. Here, I use a long-term archive of fin spine samples and three years of acoustically tagged ATS to generally expand knowledge about the ATS using the CT River and LIS, and specifically examine these empirical data for potential evidence of re-emergent spawning behavior. I analyzed 301 sections of ATS fins spines collected from 1988-2021 to determine age, annuli widths, and thus population- and individual-based growth patterns. I found that the vast majority of ATS in my study area were juveniles and sub-adults with an average (± SD) age of 7.5 ± 3.1 years and an average (± SD) length of 101 ± 26 cm. The weighed, population-based Von Bertalanffy growth model estimated a K of 0.08 (95% CL, 0.01/0.17) and a L∞ of 171.2 cm (95% CI, 129/547 cm), the latter likely showing signs of missing large adults. K and L∞ distributions showed no sign of sex-specific multi-modality. Longitudinal length back-calculations revealed the selective disappearance of faster growing phenotypes (at ages 2-6) with increasing age at capture, which is clear evidence for Lee’s phenomenon. Acoustic detections of telemetered Atlantic sturgeon (2019-2021) revealed that most sturgeon in 2019 and 2020 utilized the Lower CT River (brackish water), whereas in 2021 detections were highest in LIS (salt water). Detections in the Upper CT River (freshwater) were common but much less dense across years, with 53%, 69% and 45% of ATS detected in the Upper CT River at some point in each season (2019-2021 respectively). I found a positive relationship of fish proportion in the CT River with temperature, but an inverse relationship of fish proportion in the CT River with river discharge. On average, the arrival of fish in the CT River occurred in June, when water temperatures were 17.5 - 24.9 ºC, while the departure from the CT River generally occurred in October, coinciding with river temperatures of 15.2 - 20.4 ºC. Some of the fish utilizing the Upper CT River made directed movements to a potential spawning ground at Portland, CT (river km 47). However, these movements occurred in mid- to late August (12th -23rd), which is inconsistent with the typical spring timing of ATS spawning runs in northern populations. Fall spawning runs are only known for southern ATS populations. In addition to timing, ATS sizes in the Upper CT River also do not support spawning behavior, because fish of all sizes (72 – 154 cm TL) and ages (3-15) visited the Portland area for 0.25 – 63.25 days. I conclude that neither age nor telemetry data support the re-emergence of the CT River as an ATS spawning ground. Future work will benefit from a more even sampling of gear sizes and should examine possible explanations for ATS freshwater utilization including feeding and individual preferences.
Major Advisor: Hannes Baumann
Associate Advisor: Eric Schultz
Associate Advisor: Tom Savoy
Associate Advisor: Jacque Benway
Associate Advisor: Catherine Matassa
4 March 2022. Hannes was the invited speaker at today's Friday seminar of the Department of Marine Sciences. His talk gave an overview of the research highlights of our multi-disciplinary and multi-institutional efforts to better understand basic ecological facts, population connectivity & structure, and the unusually high CO2-sensitivity of sand lance embryos. The remotely given presentation was attended by 62 people, some of which listened in from as far away as Norway!
The talk was recorded and can be accessed via the public link below.
- Baumann, H. 2022. The unusual ecology & climate sensitivity of sand lance, a key forage fish on the Northwest-Atlantic shelf. UConn Marine Sciences Friday seminar. Online. 4 March 2022.
The unusual ecology and climate sensitivity of sand lance, a key forage fish on the Northwest-Atlantic Shelf
No matter how you look at these small, slender-bodied fishes that at times live buried in sediment or emerge as dense pelagic schools, northern sand lance (Ammodytes dubius) easily awe even the most hard-to-impress scientist or naturalist. Their unusual behavior, patchy occurrence, and reproductive timing are paralleled by their extraordinary importance as forage fish that sustain well-known hotspots of iconic predators (cod, tuna, sharks, seabirds, whales) all across the Northwest Atlantic shelf. And yet, despite their recognized role as the ‘backbone’ of many shelf ecosystems, we still don’t understand many basic aspects of sand lance ecology, population structure and their vulnerability to manmade climate change. Over the past years, our lab has been working alongside other US and Canadian research groups on multiple sand lance projects that have produced stunning new insights into these enigmatic fish. This seminar will outline some of the highlights. We discovered that the seasonal growth of these fish relies heavily on the lipid-rich copepod Calanus finmarchicus and showed that after a dormancy period in summer they spawn on Stellwagen Bank for just a brief period at the end of fall. To resolve questions of connectivity between sand lance areas, we performed large-scale Lagrangian drift simulations that suggested areas of high, low and negligible retention of sand lance offspring and showed overlaps with planned offshore wind lease areas. A large collaborative effort succeeded in obtaining specimens from across the entire distributional range (Greenland to Mid-Atlantic Bight), and subsequent whole genome sequencing newly revealed a stark genomic differentiation between northern and southern population clusters. Last, we performed multiple years of rearing experiments on embryos that consistently showed an unusual sensitivity of sand lance to future, high CO2 oceans. When coupled with regional, end-of-century pCO2 projections we estimate that rising CO2 levels alone could reduce sand lance hatching success to 71% in 2100 relative to today. Warming, acidification, and habitat exploitation therefore emerge as key factors lining up against the future productivity of this forage fish, which is so critically important across Northwest-Atlantic shelf ecosystems.
Video: A November day on Stellwagen Bank
Monday, November 22nd 2021. Big and heartfelt congratulations to Lucas Jones, who presented his Master thesis to his peers at the institute and colleagues national and international. Well done, Lucas!
A link to his recorded presentation will be posted here soon.
The UConn Department of Marine Sciences
Presents a Master’s Thesis Presentation by
B.A., University of Connecticut, 2018
4:00 p.m., Monday, November 22, 2021
Marine Sciences Building, Seminar Room 103
Using Low-Coverage, Whole Genome Sequencing to Study Northern Sand Lance (Ammodytes dubius) Population Connectivity in the Northwest Atlantic
Northern sand lance (Ammodytes dubius) are key forage fish in Northwest Atlantic (NWA) shelf ecosystems, where they exclusively occur on coarse-grain, offshore sand banks. This patchy occurrence may result in genetically more fragmented, less connected populations, but traditional morphological or genomic approaches have so far been unsuccessful in fully resolving the species’ population structure and connectivity. My study pursued an alternative genomic approach, using low-coverage, whole genome sequencing (LcWGS) to address these important questions. I extracted DNA from 273 A.dubius specimens collected by collaborators from sevenregions across the species geographical range, from Greenland to New Jersey, USA. From LcWGS data, I identified 11,558,126 single nucleotide polymorphisms (SNPs) that allowed quantifying genetic differentiation between populations (FST), thereby revealing the genetic structuring of populations throughout the NWA. Despite the potentially homogenizing influence of the general north to south ocean circulation, I found a clear genetic break around Nova Scotia that delineated a northern from a southern A. dubius supergroup. Only within the southern supergroup, genetic distances increased with the geographic distance between sample sites. At the focal site of Stellwagen Bank (southern Gulf of Maine), A. dubius samples collected over several years (2014 – 2019) revealed small but significant temporal genetic differences that imply varying occupation of this offshore habitat by genetically different sand lance contingents. Inclusion of samples from the inshore congener A. americanus confirmed the clear genetic separation between both species and further determined that all sand lance caught on Stellwagen Bank are exclusively A. dubius. Overall, my work suggests the existence of two spatially distinct A. dubius populations with little ‘realized’ connectivity, which is critical knowledge to aid protection and management of offshore marine resources.
Major Advisor: Hannes Baumann
Associate Advisor: Nina Overgaard Therkildsen
Associate Advisor: Senjie Lin
2 November 2021. We are happy report that the ICES Journal of Marine Science just published the last major experimental paper on Atlantic silverside CO2-sensitivity from our lab. Callie Concannon and co-authors report on two complementary, long-term rearing trials in 2015/16 and 2018/19, where silverside juveniles or newly fertilized embryos were reared under contrasting temperature and CO2 conditions to maturity. This revealed negative effects of high CO2 conditions on female fecundity, but only at the warm, not the cold temperature treatments (Fig. below). Our study and its data are novel, because they were generated by the first whole-life CO2 rearing experiment of a fish and are the first empirical fecundity effects shown for a broadcast-spawning fish species.
The paper is also special to us, because its publication marks the erstwhile conclusion of our yearlong, NSF-funded efforts (OCE#1536165) to understand the CO2 sensitivity and its mechanisms in this important forage fish and long-standing model in fish ecology and evolution. The project ran from 2015 - 2020, produced 15 publications, 2 book chapters, and over 40 presentations, while furthering the careers of a post-doc, a PhD student, 5 Master students and over 10 undergraduates.
- Concannon, C.A.*, Cross, E.L., Jones, L.F., Murray, C.S., Matassa, C. McBride, R.S., and Baumann, H.
Temperature-dependent effects on fecundity in a serial broadcast spawning fish after whole-life high-CO2 exposure
ICES Journal of Marine Science fsab217 (published 2 November 2021)
28 September 2021. The day started nice enough but soon turned into dark threatening clouds, which the sturgeon researchers that day eyed with concern. Tom Savoy, Deb Pacileo, and Jacque Benway from CTDEEP, along with Kelli Mosca, Steve, Jake, and Hannes started to cast off late morning and slowly motored up the Connecticut River. "We're trying to catch the slack tide to set our sturgeon gill nets" explained Tom, the veteran sturgeon researcher, who has accompanied and steered most monitoring and protection efforts of these iconic fish over the past decades. It was Tom and his colleagues, who in 2014 caught the first baby Atlantic sturgeon in Connecticut River - a potential sign for a long hoped for recovery and the starting point of our project funded by CT SeaGrant.
The day trip was almost over, before it began. The downpour short but relentless and Jacque eyeing the lightening coming from the west with unease. But just before we could decide to fully head back, the radio call from the other boat that several sturgeon had indeed been caught in the gill nets! We therefore proceeded going through the routine measurement protocol that has been implemented for many years and is part of a federal permit to study this endangered species (No. 19641). Even a photograph is considered a sample, which is why we were glad to have our photographer Jacob Snyder (RedSkiesPhotography.com) fully accredited for the trip today. We saw with our own eyes, how a caught sturgeon was first being carefully pried loose from the gill-netting and placed in an aerated observation sump to prevent stress. All individuals are then checked for previously inserted tags using a specialized scanner (1) and if none is found, a new PIT-tag is inserted under the skin with the help of a syringe (3). All sturgeon are also measured for length (2), gape (5) and head width, and weighed (6) before being released back into the water. Tissue samples and in a limited number of fish also fin spine samples are taken for genetic information and growth data, the latter Kelli analyzed for her Masters Thesis.
The potential re-emergence of Atlantic sturgeon spawning in the Connecticut River is a success story of research and conservation, however, these efforts need to be sustained and widely communicated for the success to endure.
Reposted from UConn Today | August 26, 2021 | By Elaina Hancock
The world’s oceans are becoming increasingly stressful places for marine life, and experts are working to understand what this means for the future. From rising temperatures; to acidification as more carbon enters the waters; to changes in the currents; the challenges are multifaceted, making experiments and projections difficult.
Copepods are small marine animals that are abundant, widely dispersed, and serve as major structural components of the ocean’s food web. A team of scientists from the University of Connecticut, Jinan University in China, and the University of Vermont have found that a species of copepod called Acartia tonsa can cope with climate change, but at a price. Their research was just published in Nature Climate Change.
“We have this problem of climate change and in the ocean, it is a multi-dimensional problem because it’s not just the warming, the ocean is becoming more acidic where pH is going down as we pump more CO2, into the atmosphere. Organisms need to cope, they are under more stress, and things are happening very fast,” says Hans Dam, UConn professor of Marine Sciences.
Dam explains that previous studies suggest some animals will be more sensitive than others to changes like shifts in pH. Prior studies with copepods showed they are not particularly sensitive to pH changes, but Dam points out those studies were only done with a single generation, or few generations, to a single stressor and shows the ability to acclimate rather than adapt. This new study not only looks at adaptation across 25 generations, it also considered both ocean warming and acidification (OWA), something that few studies have done until now.
“If you want to study the long-term effects, you must consider the fact that animals will adapt to changes or stress in the environment, but to do that you have to do the right experiments. Most people do not do those experiments with animals because it takes a long time to study in multiple generations.”
The researchers looked at fitness, or the ability of a population to reproduce itself in one generation, and how fitness would change through generations in increased OWA conditions. The first generation exposed to new OWA conditions suffered extreme reductions of over 50% of population, says Dam. It was as if OWA was a big hammer that greatly reduced the population fitness. By the third generation, the population seemed to have mostly recovered. However, by the 12th generation, the researchers began to see declines once again.
Though the copepods were able to adapt, the adaptation was limited because fitness was never fully recovered, and the researchers suspect there are some antagonistic interactions at play, leading to a tug of war situation between adaptation to warming and to acidification. These antagonistic interactions complicate predicting what responses can be expected.
James deMayo, co-author and UConn Ph.D. student adds, “Perhaps what’s important to emphasize with this project is that the effects of warming combined with acidification are not the same for every generation or organism that is adapting to that environment. That’s suggested by the data and why the adaptation is limited. While within intermediate generations, organisms might be very well adapted, in later generations, the effects of warming and acidification start to behave differently on the population. That’s one of the exciting parts about the research. It’s not a static, expected result for how organisms or their populations are going to continue to grow or decay.”
For example, deMayo explains, if you took individuals in later generations that had adapted to the experimental OWA conditions and placed them into the conditions of today’s ocean, they would not fare as well.
“That’s one negative consequence, that ability to not tolerate environmental shifts is a cost and an unpredicted consequence for evolutionary adaptation in a lot of systems, not just in copepods,” says deMayo.
The researchers point out that studies looking at single stressors run the risk of making overly simplified inferences about an organism’s ability to adapt, an especially risky proposition when making conclusions about such an integral component of the food web as copepods.
“Particularly when you involve living organisms, there are complexities that you can’t predict,” says Dam. “A priori, you might make the predictions, but you have no certainty that they’re going to unfold that way. In biology these are referred to as ‘emergent properties’ or things that you cannot predict from what you know in advance and this research is a good example.”
In thinking back to the hammer comparison, Dam says impacts in the copepod population have ripple effects through the whole food web and beyond.
“If fitness decreases by say, 10%, down the road we will have a 10% decrease in population size and since these animals are the main food source for fish, a 10% decrease in the world fishery is pretty significant,” says Dam. “And this is really the best-case scenario since in the lab, they’re essentially living in hotel-like conditions so that 10% isn’t taking into consideration other factors like predation or disease. In the real world we could see fitness recovery is actually much worse.”
Additionally, Dam points out another implication is that copepods sequester CO2 and reductions in their numbers reduce the ocean’s carbon sequestration capabilities, bad news at a time when more carbon sequestration is needed.
While the research offers promise for rapid adaptation, it is a reminder that as with many things in nature there’s a catch.
“There is some welcoming news, that yes, there is a recovery of fitness but there is also sobering news that the evolutionary rescue is not complete. There’s no such thing as a free lunch,” says Dam.
Groton, CT 24-26 June 2021. The long awaited and anxiously prepared virtual 44th Larval Fish Conference was held, featuring more than 240 participants from 28 countries. 58 scientific talks, including 3 keynote lectures were given via Cisco’s WebEx platform, whereas networking activities such as poster presentations, ‘Meet the Speaker’ events, and Mentor hours used the innovative Gatherly platform. The technology was working out well, the preparation paid off, and delegates were overall enthusiastic about this virtual alternative, which was forced on us by Covid-19, but may have shown us new ways and concepts to broaden the societies reach and equality.
The post-conference website is housed at https://lfc44.marinesciences.uconn.edu
Special thanks go to the scientific steering committee Eric Schultz, Jacqueline Webb, and Paul Anderson. Lauren Schaller, Anne Hill, Harley Erickson, and Kate Copeland from UConn’s conference services did a great job as well preparing and running parts of the events. Support came from NOAA’s Northeast Fisheries Science Center.
Reposted from TheCapeCodFishermen, April 28th 2021
By David N. Wiley
Bluefin tuna and striped bass crash through the waves. Seabirds wheel overhead and plunge into the water. Gape-mouthed whales rise from below. Schools of cod and dogfish hide below the surface.
While the convergence of such diverse sea life might seem accidental, those in the know thank a small, slender fish called a sand eel for the bonanza.
Also known as sand lance, these three-to-six inch forage fish are a main food source for many of the top predators in the Gulf of Maine and on Georges Bank, including some of the most commercially important species.
As their name implies, sand lance are tied to sand habitat, but not just any sand will do. To avoid predators, sand lance spend most of the night and parts of the day buried. When disturbed, they rocket out of the bottom, then dive head first and at full speed back into the sand.
As a result, their sand of choice has to be coarse enough to hold oxygen for the fish to “breathe” while buried, but soft enough to allow high-speed body penetration. One of the reasons Cape Cod is their Mecca is a band of perfect sand stretching from Stellwagen Bank along the backside of Cape Cod, past Chatham and up through Georges Bank. Whether you are a fisherman, whale watcher or seabird enthusiast, it’s this band of sand, and the sand lance that inhabit it, that makes the Cape special.
Sand and sand lance are the backbone of Stellwagen Bank National Marine Sanctuary, responsible for it being one of the top places in the United States for viewing marine life, and a centuries old, highly productive fishing ground. Yet while fishermen appreciate the importance of sand lance, little is known about their biology and most of the world does not know they exist.
To remedy the situation, a team of researchers led by scientists from Stellwagen Bank National Marine Sanctuary with partners from Boston University, Center for Coastal Studies, University of Connecticut, U.S. Geological Survey and Woods Hole Oceanographic Institution have been studying the forage fish to determine its importance and unlock some of its secrets.
One of the project’s first goals was to identify the sand lance spawning season. Using a specially designed and permitted small-mesh trawl, fished from Steve Welch’s F/V Mystic or NOAA’s R/V Auk, the team captured and examined sand lance. Thought to spawn from late fall through winter, several years of work demonstrated that sand lance on Stellwagen Bank spawn in a very narrow window at the end of November. Eggs are deposited on the seafloor and hatch after approximately six weeks.
Then things get interesting. Once hatched, sand lance are tiny, free-floating larvae for two to three months. Given this long free-floating period and the currents flowing over Stellwagen Bank, many sand lance born on the bank cannot stay there. So where do they come from and where do their offspring go?
To answer this question, the team used hydrographic modeling to backtrack to where free floating particles (like larval sand lance) would have originated prior to their sand settlement in March or April, and where drifting particles would end up two or three months after hatching.
It appears that larval sand lance settling on Stellwagen originate off the coast of Maine; years of highest sand lance abundance correspond to conditions that would have transported additional larval sand lance from as far north as Nova Scotia. The same modeling indicated that larval sand lance originating on Stellwagen Bank transport south to the Great South Channel and Nantucket Shoals (but not Georges Bank). In some years, currents moved them as far as New Jersey.
This is just another example of the interconnected world that creates a productive marine environment. Since few sand lance in the study lived past three years, the dependence on shifting currents to populate the bank could be one thing responsible for boom and bust years typical of sand lance abundance. The team is currently examining genetics of sand lance taken from throughout the Gulf of Maine, the mid-Atlantic, and eastern Canada, to gain additional insight into population structure.
Do boom-bust years influence the distribution and abundance of predators? The team investigated the association of sand lance with humpback whales and great shearwater seabirds by placing satellite tags on both species to track their movements.
Throughout the Gulf of Maine, tracking revealed that both species spend the vast majority of their time over sand lance habitat, and DNA from fecal shearwater samples showed sand lance to be the bird’s main prey. Surveys in Stellwagen also demonstrated a high co-occurrence of sand lance, humpback whales and great shearwaters.
Sand lance feed primarily from February to July, mostly on Calanus finmarchicus copepods. They stop feeding from August through October, with low levels of feeding from the end of November to January. Body growth and fat content show similar trends, with length and fat stores increasing from February to July. After July, the fish retreat to bury in the sandy bottom, conserving energy for spawning.
The team then turned its attention to the future of the valuable fish, something of extreme importance to fishermen. Ripe fish captured in November were strip-spawned on board the boats and transported to Connecticut, where eggs and larvae were raised in special tanks that allowed temperature and acidity to be manipulated to mimic future ocean conditions under climate change. Increased temperature and acidity had a dramatic negative impact on larval survival. According to Dr. Hannes Baumann, whose lab led the work, sand lance may be unusually sensitive to ocean acidification.
The future of sand lance was also a focus of team members Joel Llopiz and Justin Suca from Woods Hole Oceanographic Institution. They came to some worrisome conclusions.
The abundance of tiny C. finmarchicus copepods directly influences sand lance health: Abundant C. finmarchicus led to good parental condition and high reproductive success, while low numbers resulted in poor parental condition and poor reproductive success. Scientists have suggested climate change scenarios in the Gulf of Maine will lead to reduced abundance of this critical copepod resource. Adding to the problem was their finding that warm slope water coming through the Northeast Channel north of Georges Bank led to the death of overwintering reproductive adults.
With the Gulf of Maine warming faster than 99 percent of the world’s oceans, there is concern about the future of sand lance and its potential impact to the productivity of the Gulf of Maine, Georges Bank and other areas. While states with fisheries and other marine resources supported by sand lance cannot solve climate change issues, they can work to make sand lance more resilient to climate change. One way is to eliminate as many non-climate stressors as possible.
For example, in 2020 Massachusetts promulgated a rule limiting daily sand lance landings to 200 pounds. Rhode Island followed suit in 2021. These rules were designed to discourage the development of a commercial fishery for the species, such as the huge industrial fishery in Europe’s North Sea.
Since a commercial sand lance fishery does not currently exist here, adopting this rule by other states would be an easy, proactive way to make our waters, and the people who depend on them, more resistant to climate change disruption.
(Dr. David N. Wiley is the Research Ecologist for Stellwagen Bank National Marine Santuary. Funding for the project was provided by the Bureau of Ocean Energy Management, The Volgenau Foundation, Northeast and Woods Hole Sea Grant, International Fund for Animal Welfare, Stellwagen Bank National Marine Sanctuary and the National Marine Sanctuary Foundation. Dan Blackwood, Dr. Gavin Fay, Peter Hong, Dr. Les Kaufmann, Kevin Powers, Dr. Jooke Robbins, Dr. Tammy Silva, Mike Thompson, and Dr. Page Valentine contributed to the study)