Studies of Fine Scale Behaviour Reveal Bonefish Foraging Habits,
Swimming Speeds, and a Recovery Strategy for Anglers
Bonefish Foraging Behaviour
and Swimming Speeds
Broad-scale bonefish movements have been studied in regions
of Florida, The Bahamas, and Puerto Rico using acoustic
telemetry. This has helped us understand how bonefish use
space across daily and seasonal scales, and has even aided us
in identifying their spawning locations. While this is very useful
information for bonefish conservation, many important questions
about fine-scale bonefish behaviour remain unanswered. When
and where do bonefish forage? How fast do they swim? While
many anglers and guides have useful anecdotal insight into these
questions, they have yet to be addressed in a scientific way. Our
recent research has aimed to study these questions using
accelerometer technology.
Our first step was calibration of our accelerometer tags to allow
accurate measurement of bonefish swimming speeds (see the
sidebar [on the next page] to learn how accelerometer tags work).
This was achieved by placing tagged bonefish in a swim tunnel
(basically a treadmill for fish) and studying them as they swam at
a range of speeds. This allowed us to generate a mathematical
equation capable of estimating bonefish swimming speeds from
acceleration data. We then placed 5 accelerometer-tagged
bonefish in a mangrove wetland in Eleuthera, Out Islands, The
Bahamas, for a 5-day period and observed their behaviours,
including swimming, resting, burst swimming, drifting, and foraging.
This semi-natural environment allowed for behavioural observations
to be conducted, as well as retrieval of the tags, which is necessary
as the tags themselves store the information internally.
During this observation period, bonefish spent an average of 26%
of their time actively swimming and 17% coasting, employing a
swim and coast strategy. Bonefish were most active at dawn,
followed by the daytime. However they were also quite active at
night, which is when the most foraging behaviour was detected
of any period within the studied daily cycle. We know from
acoustic telemetry studies and visual observations that bonefish
use tidal flats at night, and our findings suggest that bonefish
likely spend more time foraging under the cover of darkness than
we previously realized. Bonefish foraged an average of 11
times/hour, searching for prey on or within the substrate. While
swimming, bonefish generally moved slowly, at a mean speed of
0.6 feet per second, but exhibited occasional burst swimming at
speeds of up to 14 to 21 feet per second across individuals. This
represents natural behaviour, as bonefish may reach even
greater speeds when taking drag, hooked up on a fly rod.Recovering Angled Bonefish
Because bonefish are such strong swimmers, they often have
little energy left after being angled. Some bonefish habitats also
have extremely high densities of their predators such as lemon
sharks and great barracuda, which take advantage of exhausted
bonefish as an easy meal. Research has found post-release
predation rates of up to 40% in some regions. This is an important
conservation issue for bonefish that is directly related to angling,
so we set out to determine what behavioural mechanisms wereThe Devil’s in the Details:
Bonefish likely spend more time foraging under the
cover of darkness than we previously realized.
[Bonefish] exhibited occasional burst swimming
at speeds of up to 14 to 21 feet per second across
individuals. This represents natural behaviour, so
bonefish may reach even greater speeds
when taking drag, hooked up on a fly rod.
J A C O B B R O W N S C O M B E , Fish Ecology and Conservation Physiology Lab, Carleton University, Ottawa, Canada
D R. A N D Y D A N Y L C H U K , Department of Environmental Conservation, University of Massachusetts Amherst
D R. S T E V E N C O O K E , Fish Ecology and Conservation Physiology Lab, Carleton University, Ottawa, Canada