Tuesday, October 4, 2011

A Baby Cadborosaur No More. Part 7: Poachers

I'm thoroughly sick of the 'reptilian hypothesis', so I'll condense my aborted article into this: the Hagelund specimen is obviously not a plesiosaur or thalattosuchian.

It is time to move on to better candidates... I want to finish this series at some point. There are several species of long-bodied poachers (Agonidae) which are compellingly similar to the Hagelund specimen. Notable shared traits include proportions, large eyes, plate-like scales, and barbels (= "whiskers"):

Atlantic Poacher (Leptagonus decagonus) from Wikipedia Commons. This isn't a candidate, but it's the closest freely available image I could find.

The anal, dorsal, and pelvic fins can fold down to the point of near-invisibility, heightening the similarity:
Hooknose (Agonus cataphractus) from Wikipedia Commons.
It appears the pectoral fins can fold significantly as well. Poachers are also flexible enough to bend the head upwards.

The poacher identification is not without its problems. There isn't any morphology which can confused for "fuzz" on the underbelly as the anal fin is rarely used in steady locomotion (Nowroozi et al. 2009) and is generally quite short anyways. Poachers are regarded as "elongated" rather than "eel-like" in the literature, with the difference apparently being that the former are tapering and the latter are thickest around the mid-point. Thus, Hagelund's drawing is at odds with his own description and poachers had to be given partial credit due to the confusion.

Hagelund's description of his specimen undulating at the surface would be highly unusual for a poacher, to say the least. The pectoral fins are the sole source of thrust, with the exception of the caudal fin being used in the C-start escape response (Nowroozi et al. 2009). Pirates Cove seems to be rather shallow and poachers can inhabit intertidal waters, but getting a poacher to the surface may also be something of a challenge; they are strongly negatively buoyant - having heavy armor and no swim bladder - and typically use ground effect (due to being within 1 cm of the bottom) in addition to the pectoral fins for lift (Nowroozi et al. 2009). Poachers are capable of swimming in the water column, and when doing so their bodies pitch upwards significantly (5-20 degrees), apparently due to their considerable density (Nowroozi et al. 2009). So unless poachers behave oddly at the surface or behavior varies substantially between species, which is always possible, this is a major problem for this candidate.

The strongest candidate is the Sturgeon Poacher (Podothecus accipenserinus) which is reasonably similar in size and coloration, but are somewhat thick-bodied and large-headed comparatively. Other possible candidates included Pallasina barbata (intertidal, similar color, however very small) and Sarritor frenatus - it should be noted that there are many other poachers in the area, but they are either far too small or deep-bodied.

Pipefish next, then everybody else.


LeBlond, P. H. & Bousfield, E. L. (1995). Cadborosaurus, Survivor from the Deep. Victoria, British Columbia: Horsdal & Schubart.

Nowroozi, B. N, Strother, J. A., Horton, J. M., Summers, A. P., & Brainerd, E. L. (2009). Whole-body lift and ground effect during pectoral fin locomotion in the northern spearnose poacher (Agonopsis vulsa). Zoology 112, 393-402. Available.

Woodley, M. A., Naish, D. & McCormick, C. A. (2011). A Baby Sea-Serpent No More: Reinterpreting Hagelund's Juvenile "Cadborosaur" Report. Journal of Scientific Exploration 25(3), 495-512.

Previous entries:
A Baby Cadborosaur No More. Part 4: What is 'Cadborosaurus'?
A Baby Cadborosaur No More. Part 5: Hagelund's Specimen And The Cadborosaurus
A Baby Cadborosaur No More. Part 6a: Cold Water on the 'Reptilian Hypothesis'
A Baby Cadborosaur No More. Part 6b: Reptilian Reproduction

Tet Zoo Coverage: 
A baby sea-serpent no more: reinterpreting Hagelund’s juvenile Cadborosaurus