Oh puffing pig fish – torn between disturbance and piscine temptations.
Noise pollution from oil and gas drilling platforms can have huge negative impacts upon marine life. However, such rigs can also act as artificial reefs, providing shelter and a hard substrate for predators and prey alike. Moreover trawling isn’t permitted close to rigs, meaning that the seabeds around them are mostly untouched.
Harbour porpoises, Phocoena phocoena, have previously been shown to change their behaviour or avoid areas as a result of unnatural noise levels. Yet a recent study by Tubbert Clausen et al. (2021) has revealed that the temptations of high prey availability can overcome such affects. The team use 21 acoustic loggers, placed on the seabed for up to 2 years to monitor noise levels and harbour porpoise activity.
They found that despite the high noise levels from the largest rig in the Danish North Sea, the porpoises were still found close to the rig, emitting echolocation noises that indicate they were hunting for fish. The platform’s artificial reef effect appeared to increase fish numbers which drew the porpoises closer.
The findings suggest that as platforms come to the end of their lifespans, they could be partially left in place to continue acting as artificial reefs – the rigs-to-reefs concept.
The first line of the sciku refers to two names for the harbour porpoise:
– The ‘pig fish’ from the Medieval Latin porcopiscus, a compound of porcus (pig) and piscus (fish).
– The ‘puffing pig’ which comes from the noise the porpoises makes when surfacing to breathe.
Shout from the rostrum: ‘Poor Carpenters in the soup!’ Such dentistry snared.
Tracking declining animal populations can be tricky enough on land, but in the ocean it’s an even harder proposition. Yet without knowledge of marine animal populations, conservation efforts can’t be directed effectively. One way to solve this issue is to examine drivers of site occupancy – what causes some populations to thrive or decline in an area. Understanding these drivers can allow researchers to predict population declines and gain insight into the probability of local population extinctions.
Sawfish are a family of rays with distinctive long, flat snouts which have horizontal teeth running along the length to resemble saws. Known as rostrums (an alternative definition to the more common meaning of a raised platform for speaking or performing from) they are packed with electroreceptors that allow them to detect prey, whilst the teeth are thought to be used in a swiping motion to incapacitate fish.
Sadly, three of the five sawfish species are Critically Endangered and the other two are Endangered. Since sawfish aren’t commonly sighted keeping track of their populations is hard and there’s little systematic monitoring. To address this Yan et al. (2021) combined data from occurrence surveys with indices of ecological carrying capacity, fishing pressure and management capacity to predict local population extinctions and identify regions where conservation efforts might be most effective.
Overfishing of sawfish is a particular threat: their fins are prized for shark fin soup (whilst sawfish are known as Carpenter sharks, they aren’t actually sharks), their teeth are used as spurs for cockfighting, their rostrum are frequently sold as novelties or trophies, and parts of them are used in traditional medicines in countries including China, Mexico, Brazil, India, Kenya and Iran.
Accidental overfishing is an issue too: their iconic rostrum and teeth are easily tangled in fishing nets and lines. What’s more, untangling sawfish from nets can be difficult and dangerous so some fishermen will kill them before bringing them aboard.
By understanding issues like overfishing and habitat loss Yan et al. were able to show that sawfish are likely to be extinct off the coasts of 55 of the 90 countries where they previously existed. Their findings also suggest that if eight nations prioritise sawfish conservation (Cube, Tanzania, Colombia, Madagascar, Panama, Brazil, Mexico and Sri Lanka), then up to 71.5% of the sawfish family’s historical global distribution would be protected.
Little Ice Age and global warming layered in a lake
By Jon Hare
Varves are annually layered sediments. I first came across the word in a study of fish scales preserved in anoxic basins off Santa Barbara, California (Baumgartner et al. 1992). Sediment cores were taken and the number and species of fish scales in the varves (layers) were used to estimate the number of anchovies and sardines off California over the past 1,700 years. The conclusion was that populations of these fish varied greatly long before commercial fishing, indicating the importance of natural variability and commercial fishing in fish population abundance.
A recent use of varves to document the past comes from Lapointe et al. (2020). They examined layered sediments in South Sawtooth Lake, Nunavut, Canada. Previous analyses demonstrated that sediment grain size in each layer (aka year) was correlated with summer temperatures; finer grained sediments were associated with cooler summers. In addition, finer grained sediments have more titanium, so by measuring titanium through the varves of sediment cores, the authors were able to reconstruct a history of summer temperatures at the site. The concept is the same as that for scales and anchovies but in this case is titanium and temperature.
The authors verified their proxy through comparison of titanium from the varves in South Sawtooth Lake to measurements of summertime North Atlantic sea surface temperature. Temperature measurements are available annually from 1854 to the present and Lapointe and team show that temperature record is significantly correlated with their titanium measurements. They then use this verified relationship to develop a 2,900 year reconstruction – one of the longest reconstructions of North Atlantic sea surface temperatures to date.
The reconstructed temperature record shows multidecadal and multicentury variability and recent change. Multidecadal variability has been observed in measurements of North Atlantic sea surface temperatures from 1854 to the present. The study by Lapointe and co-authors provides evidence that this multidecadal variability has been occurring for almost 3,000 years. Multicentuary variability was also evident; the warm and cold periods noted in history are seen in the reconstructed temperatures – the Roman Warm Period (250 BCE – 400 CE) and the Dark Ages Cold Period (400-800 CE). The coldest temperatures in the reconstruction are from the middle of the Little Ice Age (1400-1600 CE). The warmest temperatures in the 2,900 year reconstruction are from the past decade – the authors state that “the rate and magnitude of warming over the last few centuries are unprecedented in the entire record, leading to the last decade which was the warmest of the past ∼2,900 y.” Thus the authors provide strong evidence for natural variability in the climate system and evidence for rapid – unprecedented – change over the last 50 to 100 years.
Original research:
Francois Lapointe, Raymond S. Bradley, Pierre Francus, Nicholas L. Balascio, Mark B. Abbott, Joseph S. Stoner, Guillaume St-Onge, Arnaud De Coninck, and Thibault Labarre. Annually resolved Atlantic sea surface temperature variability over the past 2,900 y. Proceedings of the National Academy of Sciences, 2020; 202014166 DOI: 10.1073/pnas.2014166117. https://www.pnas.org/content/pnas/early/2020/10/06/2014166117.full.pdf
collecting fish stomach contents from file cabinets
By Jon Hare
Field studies take a lot of effort. Think of studying fishes in an estuary – where a river meets the sea. You need the expertise to know the fishes and how to take the variety of biological samples including earbones, stomachs, and gonads. You need a boat and gear to catch fish of different sizes and habits. You need to be able to deal with weather, seasons, and the other elements of nature. You need a group of people with varying expertise committed to work together. You need funding for the project. And the field effort is just the beginning – samples need to be processed in the laboratory, data compiled and analyzed, the results published, and the data made available. Now think about how many field studies or parts of field studies never make it to those final steps of dissemination. What happens to these studies? What happens to all that effort?
Hanson and Courtenay (2020) describe the fate of one such effort. A multi-year fish-related field program was undertaken from 1991 to 1993 to describe the structure and function of the Miramichi River and Estuary ecosystem in eastern Canada. After several years, the project ended owing to a change in priorities (and funding); the team of scientists and fishers went their separate ways. Some of the results were published – primarily around high profile species like Atlantic cod and Atlantic salmon. However, many of the samples and much of the data never made it to the dissemination stage of science.
The study by Hanson and Courtenay is part of an effort to recover the large amounts of field data stored in old file cabinets, on floppy disks, and in unpublished theses. In their study, Hanson and Courtenay use data collected during the Miramichi Estuary program and present detailed descriptions of the stomach contents of more than 8,000 individual fish across a range of species. Through these analyses, they describe the seasonality in the estuary both in terms of fish occurrence and diet. They also identify a small shrimp species (Crangon septemspinosa – Seven-spined Bay Shrimp) as a keystone species, linking estuarine and coastal foodwebs. Although the findings are not earth-shattering, the results and data are now available for future studies, which could model foodweb dynamics in the ecosystem (e.g. using EcoPath) or document ecosystem changes over the past three decades (a neat example from Long Island Sound, USA). Field studies and the subsequent research based on field studies are essential to developing strategies for ecosystem resilience and climate adaptation and ultimately for living sustainably within the earth system.
Original research: Hanson, J. M., & Courtenay, S. C. (2020). Data Recovery from Old Filing Cabinets: Seasonal Diets of the Most Common Demersal Fishes in the Miramichi River Estuary (Atlantic Canada), 1991–1993. Northeastern Naturalist, 27(3), 401-433. https://doi.org/10.1656/045.027.0302
Dr. Jon Hare is a scientist who works in Woods Hole, Massachusetts. His research background is fisheries oceanography and climate change impacts on marine fisheries.Check out Jon’s other sciku ‘Owls of the Eastern Ice’, ‘Varves’, ‘Signs of Spring’ and ‘Glacier Mice‘.
Shadbush (Amelanchier arborea) blooms in the spring. Clusters of small white flowers appear in March through May before leaves grow. The bloom time coincides with the upstream migration of American shad (Alosa sapidissima). Millions of shad used to return to east coast rivers, but these runs are now greatly reduced because of historical overfishing, dams, and loss of habitat.
Much like salmon, shad return to rivers to reproduce after several years at sea. Unlike salmon that reproduce and die, shad go back to sea after reproducing to return to rivers in following years to reproduce again. Thus salmon are termed semelparous from the Latin semel – once, a single time. Shad are termed iteroparous from the Latin itero – to repeat.
Shadbush is also iteroparous – blooming year after year in the spring to mark the return of the shad. Recent research by Nack et al. (2019) indicates shad migration will be earlier in the season; whether shadbush will bloom earlier remains to be seen.
Dr. Jon Hare is a scientist who works Woods Hole, Massachusetts. His research background is in fisheries oceanography and climate change impacts on marine fisheries. Check out Jon’s other sciku ‘Owls of the Eastern Ice’, ‘Varves’, ‘Cobwebs to Foodwebs’ and ‘Glacier Mice‘.
Sir Fish of the Stars. Legacy of violence reveals your true age.
The whale shark is the largest known fish species on the planet, with the longest specimen recorded at 18.8 meters. These gentle giants swim slowly through tropical waters, filter feeding on plankton and small fishes. No one is clear on how long-lived they are – like all sharks they lack the bony structures (otoliths) that are normally used to assess age in other fish species. Yet researchers now think they have the answer, and it lies in the legacy of the cold war.
Whale shark vertebrate have growth bands that increase as they age, rather like tree rings. The trouble is that without knowing how rapidly these bands form it is hard to use them to work out the age of a whale shark. Yet researchers have worked out a useful method of providing a scale for the growth bands by using the effects of nuclear weapons testing.
In the 1950s and 1960s nuclear bomb tests were carried out by countries on both sides of the Cold War, including in the atmosphere. The result of these tests is that the levels of the naturally occurring radioactive element carbon-14 temporarily increased, entering the food web – including whale shark vertebrate.
Ong et al. (2020) used radiocarbon assays of the growth bands of vertebrate from 20 whale sharks caught by the Taiwanese fishery before it was closed in 2007. They found the sampled whale sharks ranged in age from 15 to 50, and that growth bands appear to form annually. The importance of this is key to conservation efforts as understanding population structure is fundamental to understanding threats to the populations.
A note about ‘Whale shark’: Their size and nature mean that whale sharks are widely respected around the world, even featuring on the 100-peso note in the Philippines. Whale sharks are called ‘marokintana’ in Madagascar, meaning ‘many stars’ in reference to the white markings on their dark backs, whilst in Vietnam they are known as ‘ca ong’ – literally translated as ‘sir fish’.
A new species of flounder has been identified as separate from the European flounder by Momigliano et al (2018). The Baltic flounder (Platichthys solemdali sp.) is native only to the Baltic Sea – the first fish species to be identified as endemic to the area.
Its reproductive behaviour differs from the European flounder, spawning eggs that sink in coastal areas as opposed to buoyant eggs in open water. There are also differences between the species in egg morphology, egg and sperm physiology. Unfortunately, the small morphological differences mean that it is difficult to unambiguously distinguish the species and genetic methods or egg/sperm analyses are required.
Life in the ocean is under threat from a variety of manmade issues, including climate change, mining and over-fishing. Yet our understanding of marine ecosystems still remains far from complete.
New research by Unsworth et al (2018) has revealed just how important seagrass meadows are for fish populations and as a result for humanity’s fisheries. Seagrass meadows are found in the shallow seas around all the continents (aside from Antarctica) between the intertidal zone and 60 meters deep.
The researchers found that seagrass meadows provide a nursery habitat for over a fifth of the world’s largest 25 fisheries and provide support to a large number of other small-scale fisheries around the world. The study indicates that these seagrass meadows should be maintained in order to maximise their role in global fisheries production.
Every year since 2008 the College of Environmental Science and Forestry has released a Top 10 New Species list. 2018’s selection include single celled organisms, plants and animals (including twospecies of beetle) as well as a prehistoric marsupial lion identified from fossils. All 10 species are fascinating but those highlighted in the sciku are:
Protist – Ancoracysta twista, a single celled predatory Eukaryote with harpoon-like organelles that it uses to immobilise its prey. Intriguingly its evolutionary origins are unclear and it doesn’t fit neatly within any known groups.
Ape – Orangutans now come in three flavours: Bornean, Sumatran and now a newly identified Southern Sumatran species of orangutans. It is the most endangered great ape in the world.
Snailfish – Whilst snailfish are found at all depths, 2018’s species is the deepest fish in the sea, found in the Mariana Trench at 7,966 meters below the surface. It appears to be the top predator in its benthic community and is tadpole-like and around 4 inches long.
Amphipod – Epimeria quasimodo is found in the Antarctic Ocean. The 2 inch long crustacean takes its name from the hunchback of Notre Dame and has beautiful vivid colours.
Shoaling in fish can provide safety from predators and increase the effectiveness of group movement. This group efficiency can be influenced by the behaviour of individuals within the group and a measure of group coordination is the extent to which animals align with one another – termed polarisation.
Investigating female guppies, Davis et al (2017) found that groups of familiar individuals were more polarised than groups of unfamiliar individuals. This was especially apparent when the groups were in novel surroundings and reduced with habituation to their surroundings. This increased coordination suggests that groups of individuals familiar with one another may be better able to cope with challenging situations.
Many species of carp (including goldfish) can survive for months over winter in frozen lakes despite a lack of oxygen. Without oxygen they use anaerobic respiration resulting in the production of lactic acid. To avoid a deadly build up of lactic acid the fish convert it into ethanol which diffuses across their gills into the surrounding water.
Researchers have now discovered how the fish do this. During energy production in the absence of oxygen a mutated set of proteins switches the metabolic pathway within mitochondria to produce ethanol instead. The fish have two sets of these proteins, one set which is very similar to that found in other species and one set that appears to be a duplicate of the first. These sets of proteins appear to have arisen during a whole genome duplication event approximately 8 million years ago and have enabled the fish to survive in conditions other species can’t. Fagernes et al, 2017.
Gut microbes are important for digestion, nutrition and immunity, and gut microflora may impact on life expectancy. Young African turquoise killifish have diverse microbial communities but this diversity decreases over time. By feeding middle-aged killifish the microbes from younger fish, Smith et al (2017) found that the older fish lived longer and were more active in later life. Manipulating gut microbe composition may therefore be a way of delaying diseases related to ageing.
Animals navigating their environment may use a number of different spatial cues to find their way around, including the geometric structure of the environment or global landmarks. But some species are found in multiple habitat types where different cues might be more effective for navigation.
Three-spined sticklebacks live in rivers and ponds, environments which differ in terms of structure and rate of environmental change. When tested in an aquatic maze, sticklebacks collected from rivers used geometric and global cues to learn the maze, whereas sticklebacks collected from ponds only used geometric cues to navigate the maze. Within this one species of fish there appear to be multiple methods of navigation depending on the habitat in which the fish are found. Brydges et al, 2008.
Keeping your children safe is one of the most important things you can do as a parent. Cichlid fish have young that have striped patterns similar to a species of snail that sometimes lives in the same area – a form of masquerade camouflage protection. The fry only have these patterns in populations where the species of snail is present, and the cichlid parents further help their young by removing other species to snail from their territory, helping to drive up the proportions of striped snails and so increase their offspring’s charade. Satoh et al, 2017.
Sticklebacks infected with a tapeworm behave in ways that appear to maximise the tapeworm’s transmission to a new host: swimming near the surface of the water and so increasing the risk of being eaten by birds. A study by Talarico et al (2017) suggests that this change in behaviour is down to the influence of the tapeworm itself rather than a “general, systematic impairment of infected sticklebacks”, although other recent studies have demonstrated that there may also be additional reasons for this behavioural change.
Aggressive interactions between individuals can be dangerous and energetically expensive and it is important that the two competitors are able to communicate effectively to avoid such costs. When competing cichlid fish engage in agonistic interactions they are known to communicate via visual cues, but new findings suggest they also use chemical cues by urinating during encounters. Bayani et al, 2017.
Whilst the bluntnose sixgill shark is a widely known species of shark, little is known about its biology. A genetic study looking at polymorphic microsatellites revealed that individuals sampled at the same time and place were often siblings, whilst one female was found to have had up to 9 males fathering her offspring. Larson et al, 2011.
‘Translocation of freshwater fish… to new localities where they do not already exist’ is illegal in Norway. Understanding how a population of smelt has rapidly appeared in Lake Storsjoen is therefore important for population management. By using microsatellite markers Hagenlund et al (2015) were able to determine that it is likely that a large number of individuals were translocated at one time, potentially to create a population of large-sized trout, a species that feeds on smelt and is popular for fishing.
