Sciences · Anguilles de grands fonds2.8 millions d’anguilles se rassemblent au large de la Tasmanie. Cela ne signifie pas qu’elles sont à l’abri.Rédigé 28 octobre 2026 à 01:43 UTCRegarderTranscription0:07Millions of basketwork eels gather to spawn beside a single underwater mountain.0:10Researchers estimate the gathering holds about two point eight million eels, but the0:14species is globally listed as vulnerable to extinction, even with so many animals0:19concentrated in one place.0:20What can this enormous breeding gathering tell us about the species future?0:23Patience Seant lies in Juan Marine Park, south of Tasmania.0:27The eels gather about one zero meters below the surface, across reported dimensions0:31of roughly two by three kilometers.0:33That describes an extensive gathering spread through deep water.0:36A seamount is a mountain rising from the seabed.0:38At Passions, researchers have a known breeding site where they can return and0:42measure change.0:43The new work gives that monitoring a numerical starting point.0:46About two point eight million is an estimate built from surveys, rather than a count0:50of every individual fish.0:51Its immediate value is a baseline.0:53Future measurements can be compared with it to track changes at this breeding0:57gathering.0:57CSIRO led the research using surveys conducted from two thousand and twenty three1:01through two thousand twenty-five.1:03Studying fish at this depth means combining different observations.1:06Sound can survey animals through the water while a towed camera supplies images from1:10below.1:10The team combined hydroacoustic observations, which use sound with deep towed camera1:15data.1:15The dataset includes raw acoustic readings and processed measurements of returning1:19echoes.1:20Together, those observations support an estimate of how many eels occupy the1:24gathering.1:24Repeating the surveys across three years gives researchers measurements to compare1:28over time.1:29To learn whether numbers are increasing or falling, they'll need to keep making1:32those comparisons.1:33A large gathering on its own doesn't tell them the direction of change.1:36The eels gather annually and stay for months.1:39Researchers describe patients as the only known spawning aggregation of purely1:42oceanic deep sea eels.1:44That makes this a rare opportunity to study their breeding life in one identifiable1:48place.1:49The size of the gathering also has another measure: its total weight, and the1:53published figures for that measure disagree sharply.1:55Estimates of the gathering's total weight run from three point five tons to more1:59than three, five hundred tons in May.2:01That's a difference of more than a thousand fold.2:03The total weight remains uncertain, so neither figure can be treated as settled.2:07The conservation picture reaches beyond this one seamount.2:09Basketwork eels belong to a globally vulnerable species, and a concentration of2:14millions at a breeding site represents only one part of that species story.2:17A reported decline of eighty-five percent over forty years concerns a particular2:21continental slope in New Zealand.2:23It's a local warning.2:24Researchers monitoring patients need repeated measurements of this gathering to2:28understand how its own numbers change.2:30Basketwork eels are also caught as by catch, meaning they're taken while fishing2:34crews target another species here.2:36That fishing connection is orange ruffie.2:38The survey dataset includes gatherings dominated by both orange ruffy and basketwork2:42eels.2:42Parks Australia says a management plan introduced in two thousand and twenty-five2:46protects patient seamount from bottom trawling.2:48That gives this breeding habitat a specific protection.2:50Future eel surveys can track numbers there as management continues.2:54Researchers still don't know where the arriving eels come from or what happens to2:58their offspring.2:59The estimate provides a starting point for measuring change at their known breeding3:02gathering.3:03Whether protection at this one seamount is enough to sustain them will take further3:06research.Lire l’articleChronologie de l’histoireHeyDex
