The southern North Sea floor is not a landscape. It is a surface.<\/p>\n
Sand, gravel and shell, graded flat and kept that way, because a century of bottom trawling removed anything that stood up from it.<\/p>\n
The shellfish reefs that once broke that plain are gone<\/strong>.<\/p>\n Cod are not a fish of open sand. They are a fish of cracks, ledges and holes, and they use structure to ambush from and to shelter in.<\/p>\n Which leaves a large predator living over ground that offers it no cover at all.<\/p>\n So the limiting resource out there is not food. It is somewhere to be<\/strong>.<\/p>\n Drop any hard object on that seabed and two things happen in sequence.<\/p>\n First it is colonized. Barnacles, hydroids, anemones and mussels settle within months, and with them come small crustaceans and the fish that eat those.<\/p>\n Second, and this is the part that matters for cod, the object creates interior space<\/strong>.<\/p>\n A boulder makes a shadow. A pipe makes a room, with a diameter that can be chosen to suit an animal of a particular size, an entrance, an exit and a roof.<\/p>\n That is why pipe was used rather than simply more rock. Rock adds surface for food to grow on, and pipe adds refuge.<\/p>\n The cod in this experiment spent a large share of their time not swimming around the structures but inside them<\/strong>.<\/p>\n The site is a wind farm off Zeeland, on the southwestern Dutch coast, and the experiment centered on one turbine.<\/p>\n Four artificial reefs were placed around that foundation, each a heap of concrete pipes in a range of diameters.<\/p>\n Two of the four sat on granite rock scour protection of the kind already laid around turbine bases. The other two did not, which made the layout a deliberate comparison rather than a demonstration.<\/p>\n Mixed diameters are part of the design rather than an accident of supply, because a pipe wide enough to shelter a large cod is no use to a small one and the other way round.<\/p>\n Standing among the heaps are sixteen sets of listening gear, each bolted to a custom frame on a stainless steel tripod about five feet tall so the sand does not swallow the signal.<\/p>\n Packing that many close together is what gives fine scale position rather than mere presence, so a fish can be placed inside or outside<\/strong> a given pipe.<\/p>\n The whole arrangement is small. It would fit comfortably inside a city block<\/strong>.<\/p>\n Cod were caught, fitted with acoustic transmitters and released at the site in two batches, 45 in July of 2021 and another 19 in May of 2022.<\/p>\n The tags carried pressure and acceleration sensors as well, so depth and activity came back alongside position.<\/p>\n Tracking ran to January of 2023, about eighteen months end to end, and the results were published in the summer of 2024.<\/p>\n Site fidelity and residency both came out high. Fish that found a reef tended to stay with it and to return to it.<\/p>\n There was no meaningful difference between the reefs with rock scour beds and the ones without, which suggests the pipes were doing the work.<\/p>\n And only a handful of individuals stayed through winter<\/strong>, which is the finding that gets left out most often<\/strong>.<\/p>\n This is the oldest argument about artificial reefs and it is not settled by this study.<\/p>\n A structure that concentrates fish has either created new ones or gathered up existing ones from a wide area, and telemetry cannot separate those two.<\/p>\n Concentration on its own can make a population easier to catch rather than larger, which is why reefs and fishing closures usually go together.<\/p>\n The second batch of fish also only had about eight months of tracking rather than eighteen, so the headline period does not apply to all 64, in the way that a seeded stone bed<\/a> or a tagged marine predator<\/a> gets reported as one clean number<\/strong>.<\/p>\n The paper itself frames the result as strong attraction rather than proven benefit, describing site fidelity and residency<\/a> and stopping carefully short<\/strong>.<\/p>\n The practical question sits at the other end of the project life.<\/p>\n Offshore wind consents in the North Sea generally require full removal of everything installed, including the scour rock, which was written to protect the seabed from industrial leftovers.<\/p>\n Twenty five years of colonization turns that clause into an instruction to demolish a reef that the surrounding fishery has come to depend on.<\/p>\n Deliberately adding refuge structures makes the conflict sharper rather than softer, because it makes the habitat intentional, as the project’s own writeup<\/a> acknowledges.<\/p>\n The concrete pipe<\/strong> was never about the concrete.<\/p>\n It was about the hole in it<\/strong>.<\/p>\n","protected":false},"excerpt":{"rendered":" The southern North Sea floor is not a landscape. It is a surface. Sand, gravel and shell, graded flat and kept that way, because a century of bottom trawling removed anything that stood up from it. The shellfish reefs that once broke that plain are gone. Cod are not a fish of open sand. They are … Read more<\/a><\/p>\n","protected":false},"author":28,"featured_media":37281,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"rank_math_focus_keyword":"piles","rank_math_title":"Piles of concrete pipe were dropped around 1 turbine foundation off the Dutch coast and tagged cod moved in and stayed, where the flat swept sand around them offers nothing to hide inside at all","rank_math_description":"Researchers dropped concrete pipes beside a wind turbine off the Dutch coast, tagged 64 cod, and found the fish returning to the same spot for 18 months s","footnotes":""},"categories":[8],"tags":[],"class_list":["post-37093","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-energy"],"_links":{"self":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/37093","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/users\/28"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/comments?post=37093"}],"version-history":[{"count":3,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/37093\/revisions"}],"predecessor-version":[{"id":37129,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/37093\/revisions\/37129"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/media\/37281"}],"wp:attachment":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/media?parent=37093"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/categories?post=37093"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/tags?post=37093"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}What a hole of the right size is worth<\/h2>\n
Four heaps around a single monopile<\/h2>\n
Sixty four fish and eighteen months of pings<\/h2>\n
Attraction is not the same as production<\/h2>\n
What happens when the turbine comes down<\/h2>\n