Hannah Owens
@hannahoish.bsky.social
She/her. Fixed-term Assistant Professor; Center for Macroecology, Evolution, and Climate and Center for Global Mountain Biodiversity; Globe Institute; Copenhagen University. Ecology & evolution w/ natural history collections and R. #FishADay
#FishADay Scalicus engyceros An armored searobin with no English common name. Benthic, deep Pacfic, often associated with seamounts. Skitters along the seafloor on spidery "legs" that are actually modified pectoral fin rays.
www.eurekalert.org/multimedia/1...
www.eurekalert.org/multimedia/1...
Walking Behavior in Peristediid Fishes in the South China Sea
This video documents the distinctive benthic [deep-sea] behaviors of three peristediid (armored searobin) fishes observed in the South China Sea: Scalicus engyceros, Paraheminodus murrayi and Per...
www.eurekalert.org
September 21, 2026 at 3:59 PM
#FishADay Scalicus engyceros An armored searobin with no English common name. Benthic, deep Pacfic, often associated with seamounts. Skitters along the seafloor on spidery "legs" that are actually modified pectoral fin rays.
www.eurekalert.org/multimedia/1...
www.eurekalert.org/multimedia/1...
#FishADay Chirolophis decoratus Decorated Prickleback. Neritic--prefers hiding in shallow rocky habitats in N. Pacific from Kamchatka to Humboldt Bay. Elaborate cirri on head may help camouflage. Lays eggs in a mass which are guarded until hatch by males or females. youtu.be/5ZLJ2_Af0p4
Rare Footage of Decorated Warbonnet Guarding Eggs
YouTube video by ScubaMoto
youtu.be
September 18, 2026 at 8:31 AM
#FishADay Chirolophis decoratus Decorated Prickleback. Neritic--prefers hiding in shallow rocky habitats in N. Pacific from Kamchatka to Humboldt Bay. Elaborate cirri on head may help camouflage. Lays eggs in a mass which are guarded until hatch by males or females. youtu.be/5ZLJ2_Af0p4
#FishADay Sebastes melanops Black Rockfish. NE Pacific coast from Alaska to southern California. Croak, knock, and grunt by vibrating their swim bladders. One of a few species a recent study was able to identify just based on sound. Move over, birders! theconversation.com/scientists-h...
Scientists have identified unique sounds for 8 fish species
Researchers have known for centuries that some fish make sounds. Now, using special underwater acoustics, researchers have been able to identify sounds from eight different species.
theconversation.com
September 16, 2026 at 11:03 AM
#FishADay Sebastes melanops Black Rockfish. NE Pacific coast from Alaska to southern California. Croak, knock, and grunt by vibrating their swim bladders. One of a few species a recent study was able to identify just based on sound. Move over, birders! theconversation.com/scientists-h...
#FishADay Trachurus murphyi Chilean Jack Mackerel. Epipelagic South Pacific. One of the species being substituted in for NE Atlantic "true" mackerel, which has been declining. Of course, T. murphyi is also declining... www.ft.com/content/980a...
UK canned ‘mackerel’ now contains no mackerel
Critics say switch to tins comprising more sustainable species risks confusing consumers
www.ft.com
September 15, 2026 at 10:52 AM
#FishADay Trachurus murphyi Chilean Jack Mackerel. Epipelagic South Pacific. One of the species being substituted in for NE Atlantic "true" mackerel, which has been declining. Of course, T. murphyi is also declining... www.ft.com/content/980a...
#FishADay Retropinna tasmanica Tasmanian Smelt. Endemic to Tasmanian waters; breed in coastal estuaries and lowland streams, mature in open ocean. Also, like many other smelts and relatives, they smell like cucumber. That's about all that's known about them. link.springer.com/article/10.1...
Crying wolf, crying foul, or crying shame: alien salmonids and a biodiversity crisis in the southern cool-temperate galaxioid fishes? - Reviews in Fish Biology and Fisheries
The galaxioid fishes are the dominant, most speciose group of freshwater fishes (with >50 species) in the lands of the cool southern hemisphere, with representatives in western and eastern Australia, ...
link.springer.com
September 14, 2026 at 2:28 PM
#FishADay Retropinna tasmanica Tasmanian Smelt. Endemic to Tasmanian waters; breed in coastal estuaries and lowland streams, mature in open ocean. Also, like many other smelts and relatives, they smell like cucumber. That's about all that's known about them. link.springer.com/article/10.1...
#FishADay Helostoma temminckii Kissing Gourami. Native to still, FW in continental SE Asia and nearby islands, introduced more broadly across Asia, popular in pet trade. Some host parasitic algae, but of course most notable for mouth fighting behavior.
File:Helostoma temminkii kissing.ogv - Wikimedia Commons
commons.wikimedia.org
September 11, 2026 at 2:22 PM
#FishADay Helostoma temminckii Kissing Gourami. Native to still, FW in continental SE Asia and nearby islands, introduced more broadly across Asia, popular in pet trade. Some host parasitic algae, but of course most notable for mouth fighting behavior.
#FishADay Ameiurus nebulosus Brown Bullhead. FW Atlantic and Gulf Slope drainages of NA. First fish species documented to host a transmissible cancer--in this case, a melanoma that doesn't seem to be particularly deadly. www.nature.com/articles/d41...
Rare contagious cancer discovered in wild catfish
Transmissible tumours have been found in only a few types of animal, but there might be many more out there.
www.nature.com
September 10, 2026 at 2:28 PM
#FishADay Ameiurus nebulosus Brown Bullhead. FW Atlantic and Gulf Slope drainages of NA. First fish species documented to host a transmissible cancer--in this case, a melanoma that doesn't seem to be particularly deadly. www.nature.com/articles/d41...
#FishADay Solenostomus snuffleupagus Hairy Ghost Pipefish. Newly described from material collected in early 90s off Queensland. "Hair" actually skin filaments that help it blend in with reef macroalgae. Only ~3cm long--no wonder it went long undetected www.scientificamerican.com/article/a-re...
A real Mr. Snuffleupagus? Meet the ocean’s strangest new fish species
A strange, tiny fish that resembles the famous Sesame Street character camouflages amid red algae thanks to its flamboyant reddish “hairs”
www.scientificamerican.com
September 9, 2026 at 8:27 AM
#FishADay Solenostomus snuffleupagus Hairy Ghost Pipefish. Newly described from material collected in early 90s off Queensland. "Hair" actually skin filaments that help it blend in with reef macroalgae. Only ~3cm long--no wonder it went long undetected www.scientificamerican.com/article/a-re...
#FishADay Bassozetus robustus Robust Assfish. Deep sea down to 4000+m? Global? But might also be several species that should be split up. youtu.be/rktnlbkGUJc?...
Black Hole: Bassozetus
YouTube video by Caladan Oceanic
youtu.be
September 8, 2026 at 9:01 AM
#FishADay Bassozetus robustus Robust Assfish. Deep sea down to 4000+m? Global? But might also be several species that should be split up. youtu.be/rktnlbkGUJc?...
#FishADay Conger conger European Conger. Eastern Atlantic, rocky near-shore habitats. Maxing out at ~3m and ~72kg, world's heaviest eel. Migrate to deep water to spawn and die. youtu.be/9hLWgXoEXU4?...
CONGER EEL Monster of the Deep in UK Waters
YouTube video by Dave's Cave
youtu.be
September 7, 2026 at 7:27 AM
#FishADay Conger conger European Conger. Eastern Atlantic, rocky near-shore habitats. Maxing out at ~3m and ~72kg, world's heaviest eel. Migrate to deep water to spawn and die. youtu.be/9hLWgXoEXU4?...
#FishADay Demogorgonichthys arcanus Demon Cave Fish. One cave system in northern Alabama. Eyeless; appears to have lost its vision following an evolutionary pathway separate from a close blind relative that is found in the same system! www.scientificamerican.com/article/newl...
Newly discovered ‘demon cave fish’ hid out in Alabama military installation for 40 years
Scientists named this oddball creature after the Demogorgon from Stranger Things
www.scientificamerican.com
September 4, 2026 at 8:32 AM
#FishADay Demogorgonichthys arcanus Demon Cave Fish. One cave system in northern Alabama. Eyeless; appears to have lost its vision following an evolutionary pathway separate from a close blind relative that is found in the same system! www.scientificamerican.com/article/newl...
#FishADay Notropis percobromus Carmine Shiner. Eastern North America from Manitoba to Arkansas; mostly in river and stream pools w/ some current. Breeding males sport bright red heads. Overall IUCN least concern, but federally listed in Canada. www.dfo-mpo.gc.ca/about-notre-...
Aquatic Species at Risk, Carmine Shiner (Notropis percobromus)
Aquatic Species at Risk, Carmine Shiner (Notropis percobromus)
www.dfo-mpo.gc.ca
September 3, 2026 at 2:36 PM
#FishADay Notropis percobromus Carmine Shiner. Eastern North America from Manitoba to Arkansas; mostly in river and stream pools w/ some current. Breeding males sport bright red heads. Overall IUCN least concern, but federally listed in Canada. www.dfo-mpo.gc.ca/about-notre-...
#occCite version 0.6.3 is now on CRAN, ready for the #rgbif changeover to Catalog of Life Extended release taxonomy. #Rstats #RopenSci docs.ropensci.org/occCite/news...
Changelog
docs.ropensci.org
September 2, 2026 at 8:49 AM
#occCite version 0.6.3 is now on CRAN, ready for the #rgbif changeover to Catalog of Life Extended release taxonomy. #Rstats #RopenSci docs.ropensci.org/occCite/news...
#FishADay Cottus cognatus Slimy Sculpin. Nocturnal, cold streams and lakes from northeast Canada to eastern Siberia. Invasive Round Gobies may be muscling them out of their favorite nesting spots, as well as snarfing up eggs and young.
www.greatlakesnow.org/2023/06/19/i...
www.greatlakesnow.org/2023/06/19/i...
I Speak for the Fish: Searching for the elusive sculpin - Great Lakes Now
Sculpin are masters of camouflage and only the most discerning of observers will ever spot one.
www.greatlakesnow.org
August 31, 2026 at 12:14 PM
#FishADay Cottus cognatus Slimy Sculpin. Nocturnal, cold streams and lakes from northeast Canada to eastern Siberia. Invasive Round Gobies may be muscling them out of their favorite nesting spots, as well as snarfing up eggs and young.
www.greatlakesnow.org/2023/06/19/i...
www.greatlakesnow.org/2023/06/19/i...
Ecological niche modelers, seasoned and new! This is a really nice review of causes of and potential solutions to over-fitting. It's also a great guide to generally improving your niche models, and a reminder that good fit stats do not always mean good models. onlinelibrary.wiley.com/doi/10.1111/...
When Good Fit Goes Bad: Identifying and Minimising Overfitting in Ecological Niche Models
Aim To synthesise current understanding of overfitting as a pervasive and often underdiagnosed problem in correlative ecological niche models (ENMs), and to assess its consequences for model interpr...
onlinelibrary.wiley.com
August 5, 2026 at 3:14 PM
Ecological niche modelers, seasoned and new! This is a really nice review of causes of and potential solutions to over-fitting. It's also a great guide to generally improving your niche models, and a reminder that good fit stats do not always mean good models. onlinelibrary.wiley.com/doi/10.1111/...
The fish in 4D tour continues! If you’re attending #JMIH26 this week and want to hear what 3D distribution models through time might have to tell us about a classic marine biogeographic pattern, stop by my talk on Friday morning. I’ll also be handing out #voluModel hex logo stickers all week!
July 7, 2026 at 10:32 PM
The fish in 4D tour continues! If you’re attending #JMIH26 this week and want to hear what 3D distribution models through time might have to tell us about a classic marine biogeographic pattern, stop by my talk on Friday morning. I’ll also be handing out #voluModel hex logo stickers all week!
Attention, biodiversity scientists! The #occCite #R package is back on CRAN after a spring sabattical brought on by dependency changes. Thanks for your patience, and enjoy once again being able to more easily and robustly cite the sources of large biodiversity datasets!
docs.ropensci.org/occCite/
docs.ropensci.org/occCite/
Querying and Managing Large Biodiversity Occurrence Datasets
Facilitates the gathering of biodiversity occurrence data from disparate sources. Metadata is managed throughout the process to facilitate reporting and enhanced ability to repeat analyses.
docs.ropensci.org
June 29, 2026 at 1:26 PM
Attention, biodiversity scientists! The #occCite #R package is back on CRAN after a spring sabattical brought on by dependency changes. Thanks for your patience, and enjoy once again being able to more easily and robustly cite the sources of large biodiversity datasets!
docs.ropensci.org/occCite/
docs.ropensci.org/occCite/
And this is why you have to be careful about model extrapolation! #mop #mess #enm Thanks, as always, to @xkcd.com for providing premium content for my stats lectures.
imgs.xkcd.com/comics/messi...
imgs.xkcd.com/comics/messi...
June 18, 2026 at 7:51 AM
And this is why you have to be careful about model extrapolation! #mop #mess #enm Thanks, as always, to @xkcd.com for providing premium content for my stats lectures.
imgs.xkcd.com/comics/messi...
imgs.xkcd.com/comics/messi...
New #voluModel update out! We're up to v 0.2.4, with new functions to partition occurrences and background points into 3D blocks, and make modeling with Maxent easier! #R hannahlowens.github.io/voluModel/in...
Modeling Species Distributions in Three Dimensions
Facilitates modeling species' ecological niches and geographic distributions based on occurrences and environments that have a vertical as well as horizontal component, and projecting models into thre...
hannahlowens.github.io
May 26, 2026 at 3:23 PM
New #voluModel update out! We're up to v 0.2.4, with new functions to partition occurrences and background points into 3D blocks, and make modeling with Maxent easier! #R hannahlowens.github.io/voluModel/in...
April 23, 2026 at 8:22 AM
April 20, 2026 at 1:08 AM
I know #FishADay hasn't exactly been every day lately and it's not actually a fish, but while diving on vacation in Lanyu this week we saw a cuttlefish and I can't stop thinking about it,
April 15, 2026 at 7:00 AM
I know #FishADay hasn't exactly been every day lately and it's not actually a fish, but while diving on vacation in Lanyu this week we saw a cuttlefish and I can't stop thinking about it,
Looking forward to seeing some familiar faces and making new connections at Species on the Move 2026. Also presenting-- maybe I'll see you there? #SOTM2026 #SOTM26 #SpeciesOnTheMove #Taiwan #Nantou
April 12, 2026 at 4:08 AM
Looking forward to seeing some familiar faces and making new connections at Species on the Move 2026. Also presenting-- maybe I'll see you there? #SOTM2026 #SOTM26 #SpeciesOnTheMove #Taiwan #Nantou