SCUBA November 2022 Issue 130 | Page 45

Baltic Sea gas leaks
Cave divers uncover skeleton
Field notes from the Nursery Shark Trust MD Paul Cox reports on new research on tiger shark breeding and birthing zones , and its implications for future conservation

Baltic Sea gas leaks

Sabotage is the most likely cause of leaks in two Baltic Sea gas pipelines between Russia and Europe , European leaders have said , after seismologists reported explosions around the Nord Stream pipelines . A seismograph on the Danish island of Bornholm , near where the leaks occurred , twice recorded spikes on the same day in September on which the Nord Stream 1 and 2 gas pipelines reported dramatic falls in pressure . A Danish military flight over the leaks brought back striking images from the ruptures , including one showing an area of bubbling gas a kilometre wide on the sea ’ s surface .

Cave divers uncover skeleton

A prehistoric human skeleton has been discovered by divers in a Mexican cave system flooded at the end of the last ice age . Marine Archaeologist Octavio del Rio said he and fellow diver Peter Broger saw the shattered skull and skeleton partly covered by sediment in a cave in an area where the Mexican government plans to build a high-speed tourist train through the jungle . Given the distance from the cave entrance , the skeleton could not have been positioned there without modern diving equipment , so it is possibly 8,000 years old , Mr del Rio said , referring to the era when rising sea levels flooded the caves .

Field notes from the Nursery Shark Trust MD Paul Cox reports on new research on tiger shark breeding and birthing zones , and its implications for future conservation

Perhaps not completely surprising but important nevertheless , a new study out this summer has shed new light on the movements and habits of tiger sharks . According to the authors of “ Age-Dependent Dispersal and Relatedness in Tiger Sharks ( Gelocerdo cuvier )”, both male and female tiger sharks repeatedly visit the same areas to reproduce . Meaning that , despite roaming vast tracks of the world ’ s ocean , these big predators are remarkable creatures of habit .

As what might be described as a ‘ dormant ’ scientist , when I saw this pop up in the news , I did what I ’ ve been taught to do and sought out the original scientific paper . And as a dormant scientist , reading it had the effect of making my brain hurt . Scientific writing is a complex code , honed over years , to describe a process with absolute precision . If you ’ re not used to reading it , you really have to focus . And keep starting again . Anyway , suffice to say , for such a ‘ simple ’ conclusion , the research team had to jump through a fair number of hoops . Comparing data from tracking with DNA analysis and systematically removing animals of different sizes and sexes to focus in on the important signals
in the data . It ’ s a complex picture but , if you make the effort , it ’ s an interesting set of conclusions .
Tagging studies in the past have provided evidence that females return to favoured pupping grounds over many cycles . But the pattern detected for males has been less clear . Why would they need to return ? It ’ s not like they play any role in the pups ’ early years . Or do they visit pupping grounds to snack on the young sharks ? Well , this latest study provides some clarity . The DNA data , once untangled , show both males and females “ returning to base ”, implying that these areas are not only places for birthing but also for meeting a mate . Why leave it to chance in the open ocean ? If you want to meet a mate , just pop into the nursery ! And so the circle of ( tiger shark ) life , rolls on .
The point in all of this , comes back to conservation . While this is all great to know , from the perspective of protecting the species it places particular importance on these areas . And on the ability of science , and scientists , to do the hard work of searching through the clues to find out what makes these incredible animals tick . www . sharktrust . org
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