1) What a wonderful day of wildlife watching near Plymouth. To learn why the incredible bluefin tuna have migrated to UK seas and also much more, read this thread. It is vital to understand the reason for their recent appearance. See 2 
2) This article "Why are bluefin back in UK seas" (not my image) that I wrote in January's Fishing News describes why Tuna are here, but the following thread goes into more interesting details abut bluefin tuna and other species. See 3fishingnews.co.uk/news/why-are-b…
3) Tuna are among the animals at the top of the marine food chain that begins with the plankton. Plankton are cold-blooded like nearly all other creatures in the sea. All species have a thermal preference and cold-blooded animals live where the temperature is suitable. See 4
4) In the northeast Atlantic, off the UK coast, the sea has warmed and the zooplankton community has moved north by over 10˚ latitude in the last 50 years. Warm-water copepods have advanced north and cool-water copepods have retreated polewards. . See 5seaturtle.org/PDF/BeaugrandG…
5) The warming of the sea and the movement of the plankton has influenced the distribution of the other cold-blooded species that feed upon them from fish to whales . (To read the full text for free, request a copy from the author hjalmarh@frs.fo) See 6sciencedirect.com/science/articl…
6) Bluefin tuna started reappearing in UK seas about 12 years ago. I, along with colleagues, explained why in our 2019 article in the journal 'Science Advances', it is free to read here: . See 7science.org/doi/10.1126/sc…
7) Simply, the north Atlantic bluefin tuna population seesaws northwards and southwards depending upon climate and its effect on sea temperature. This graphic explains. See 8
8) Bluefin tuna are not the only warm-water species appearing in our seas, however. Recreationally, an angling 'club record', 3 lb 15 oz bonito (Sarda sarda) was caught off north Devon this summer: . See 9northdevonanglingnews.co.uk/2023/08/16/clu…
9) The north Devon club record Bonito beat a 3lb 8 dr Atlantic bonito caught 8 years earlier at Hartlepool Heugh in North East England in 2015: . See 10facebook.com/seaanglermag/p…
10) But bonito have been visiting UK seas for a while perhaps, unsurprisingly, appearing around the time of reappearance of bluefin tuna. Here, is a report of Atlantic bonito caught in the North Sea in 2010: . See 11thefishsite.com/articles/atlan…
11) Gilthead sea bream (Sparus aurata), another southern, warmer-water species, are now caught frequently, in the English Channel and off Ireland: . See 12researchgate.net/publication/28…
12) Red mullet (Mullus surmuletus) have increased in seas around Scotland since 1995 after being absent for the 70 years before (the text says numbers have soared): . See 13researchgate.net/publication/24…
13) This paper deals with geographical shifts of several fish and gives projections of putative future abundances: . See 14besjournals.onlinelibrary.wiley.com/doi/10.1111/13…
14) Lower down the food chain, among invertebrates, Cornish fishermen reported ‘unprecedented numbers’ of common octopus (Octopus vulgaris) in 2023 . See 15theguardian.com/uk-news/2022/j…
15) The warm water spiny lobster, (Palinurus elephas) is currently increasing in abundance in western Cornish waters: secure.toolkitfiles.co.uk/clients/17099/…. (While the increase in spiny lobster is explained in that article by successful conservation measures, I suspect their previous decline and recent increased presence may also be a result of climate-driven, biogeographical shifts; warmer seas bringing their return.) See 16
16) Returning to the plankton. Along with my colleague Gregory Beaugrand, I wrote about the ramifications of their northwards movement for the biology of the North Sea here: . See 17royalsocietypublishing.org/doi/10.1098/rs…
17) Here is a popular media article written about the paper in the previous post above . See 18wired.com/2009/10/north-…
18) Here again, is the summary graphic about bluefin tuna as this species portrays well, what may be occurring in seas around our coasts; a north-south, seesaw-like, climate-induced shift of north Atlantic bluefin tuna and other species. . See 19 science.org/doi/10.1126/sc…
19) In order to exploit fish sustainably it is fundamentally, important to understand "Why is What Where”. Failure to do so means we act in ignorance, which is why I wrote the article (post 2) for Fishing News in January this year about the reappearance of bluefin tuna in UK seas . See 20fishingnews.co.uk/news/why-are-b…
20) There is now, more to add to our 2019 bluefin story that the reappearance of bluefin in our seas due to a phenomenon called the AMO (Atlantic Multidecadal Oscillation), which was thought to be a reproducible north Atlantic climate cycle. See 21
21) The AMO is now realised to be an artefact of several warming and cooling factors over the last centuries that appeared to give a cyclical effect; notably, volcanic forcing and, See 22science.org/doi/10.1126/sc…
22) Ocean circulation. As a result climate variation and sea surface temperature in the northeast Atlantic is not a result of a predictable, internal cyclical, climatic forcing but it is unpredictable . See 23royalsocietypublishing.org/doi/full/10.10…
23) Those papers (20 and 2) describing the demise of the AMO as a feature don't change the results of our 2019 study on the early 21st century, northwards movement of bluefin tuna. What it does change however, is the expectation that climate will reverse and the region will cool. See 24
24) The lack of a predictable climate cycle therefore removes an expectation that bluefin might retreat southwards once again; the fish may be here to stay this time if climate continues to warm. See 25
25) With the current climate-driven warming of north Atlantic seas, the ‘demise of the AMO’ has implications for bluefin tuna and the broader biology of the region, which we have discussed here: (Contact me for a free copy if interested.) See 26int-res.com/abstracts/cr/v…
26) Future biogeographical movements of species must be considered in fisheries management as this excellent Carnegie Endowment article on the tragedy that has befallen Atlantic mackerel describes . See 27carnegieendowment.org/research/2023/…
27) Simply put, UK seas have warmed causing a northwards biogeographical shift in species from the plankton at the base of the food chain to fish like cold-water mackerel that have decreased in abundance and warm-water tuna that have increased in abundance. See 28
28) Just like the disappearance and appearance of bluefin tuna in UK seas, changes in the abundance of mackerel in the Southwest Approaches to the UK are not a new phenomenon …. See 29cefas.co.uk/publications/l…
29) A few months prior to the publication of the Carnegie article we proposed a new approach to fisheries management that includes environmental change, we used North Sea cod as an example; the paper is here . See 30nature.com/articles/s4200…
30) Here is a media-friendly article in Fishing News about the paper above . See 31fishingnews.co.uk/features/fishe…
31) In the preceding thread I have tried to show why southern marine species have moved northwards to explain the changes we are seeing in UK seas and to help us understand the fundamental question, "Why is What Where?".
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