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[Non-ceph] Shark tagging and diet

Steve O'Shea

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We've quite a number of interesting projects running right now. One involves tagging and releasing sharks in a harbour just west of us, the Manukau Harbour. This wee fellow, caught 2 days back (I'd had enough of work and went fishing!) is a fully mature male spotted dogfish, but Nik (one of the dark and dastardly lads doing his research here) has poked tags in seven gills, school sharks and spikey dogfish so far (~ 45 tagged shark swimming around out there), some to ~ 7 feet long.

Prior to this work another student was looking at the diet of several fish species throughout the region, and from ~ 20 school shark pups recorded three species of squid; records from the Manukau Harbour were the first records (ever) of squid from the region (that I'm aware of (we have very little information on what occurs in this harbour)). In a related project, sadly, heavy metal concentrations (Cd, Zn, Pb and Cu) are shown to all exceed food quality standards in both liver and often fillet tissues, not just in shark but in three other species as well - such is the level of polution! (We make the most of the samples we catch; diet, age, heavy metals ... everything is interconnected.)

Here's a pic of the spotted dogfish, sporting its new yellow tag. Of the 45-or-so that we've tagged so far we've not had a single recapture. We return to the exact same area every week, so obviously they move on (we're trying to determine shark migratory patterns/residency behaviour).

The shark species we're targetting, bronze whaler, hasn't entered the harbour yet; they get considerably(!!!!) larger, and would not be handled in the boat for sure(!!!!).

The lower image is of Eduardo (he studies frogs, but loves fishing) with one of the 'normal' baits we use to catch the big ones. This is an expensive game!
 

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cthulhu77

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'Ware for your arms, with a bronze whaler! Would hate to see you having to hoist pints with only one mitt!
 

Steve O'Shea

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Here's a pic that Kat took several weeks ago (hope you don't mind TTF) of Nik and a small seven gill, also sporting a yellow tag (base of dorsal fin).

These animals are wicked cool!!

This weekend we're going to a new spot, using ~ 500kg of sunfish as burley (we're filleting a 3m x 2m sunfish in the car park this Friday coming; will try and clean the bones to articulate them).
 

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Steve O'Shea

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Just for a minute I thought you were going to beat me again:goofysca: ! Ta
 

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