What should a hydrozoan observation record include?

Fix the observation in place and time

Begin with the date and time, including the time zone if observations will be compared across locations. Record coordinates when appropriate and safe, or describe the shore position precisely enough to relocate the area. For a dive or water-column observation, include depth and how it was measured; for a shore find, note the tide state or position relative to a stable landmark if known. These details give the image an ecological setting without assuming that every organism remains in one place.

Write the substrate or attachment surface in plain terms: rock, pier piling, kelp, shell, or another observed surface. If the organism is drifting or detached, say that rather than guessing where it originated. A record such as “attached to shaded underside of a harbor piling at approximately two meters” is more informative than “near shore.”

Describe the form before naming it

Note whether the subject appears as a colony, a single medusa, or an uncertain form, and describe visible features such as branching, spacing, bell outline, or tentacles. Use cautious language when the image does not show enough detail. “Branching colony, pale translucent, tips indistinct” is an observation; a species name is an interpretation that needs diagnostic support. If you use a guide, record its title or reference and which features matched.

Photograph the subject from more than one angle when possible. Include a scale in the same plane as the organism, not far in front of or behind it, since perspective can make the size misleading. Keep an original image and identify any cropped or adjusted versions. A ruler, scale card, or known object can help, but note the scale method.

Track confidence and conditions

Assign confidence in a way that explains its basis. For example: “high confidence at group level because branching colony form and diagnostic structures are visible; species unresolved.” This is more useful than a bare number. Record water visibility, lighting, current, and camera limitations if they affect interpretation. If the subject moved or the image was blurred, note that too.

A compact entry might read: “2026-05-14, north side of the rock ledge, 3 m depth; colony attached to rock; scale card in frame; branching form visible, terminal structures blurred; hydrozoan likely, species undetermined; moderate confidence.”

Make the record reviewable

Keep image filenames or identifiers tied to the notebook entry, and preserve the context needed to find the original. If another observer later revises the identification, add the new assessment and reference rather than silently replacing the first. Good records make uncertainty legible and allow future readers to separate what was seen from what was concluded.