Habitat suitability and the effect of physical parameters on Finless Porpoise (Neophocaena phocaenoides) in the Khorkhoran wetland

Abstract

Introduction: Identification of the marine mammals’ suitable habitats is one of the
requirements for coastal ecosystem conservation plans in southern Iran.
Materials & Methods: A total of 42 points of Finless Porpoise (Neophocaena
phocaenoides) presence were collected based on direct and random observation from late
autumn to late winter of 2021. Depth map was created using a logarithm ratio model with
a coefficient of determination of 0.784 and along with bed slope, channel width, average
channel depth and width, channel length, channel width ratio and channel depth ratio
(relative to the channels connected to it) were submitted into the Maxent model as
predictor variables. The porpoise habitat suitability map was produced with an area under
the curve of 0.887 for training and 0.832 for test data.
Results: According to the results of the Jackknife test, depth with an S-shaped response
curve had the largest contribution (50.23%) to predicting suitable habitats of the porpoise.
The suitability of the porpoise habitats increased with increasing depth and average
channel depth, while the probability of the species' presence decreased with increasing
slope, channel width, average channel width and channel length. The two variables of
channel width ratio and channel depth ratio had insignificant effects on the probability of
the species' presence. Moreover, an area of 4400 ha (10.6% of the total area) was identified
as suitable habitat.
Conclusion: Since these areas cover a small percentage of the study region and
commercial fishing is performed more in such deep areas than the shallow waters, it is
important to protect deep waters and reduce the resulting conflicts of interest with humans,
thus ensuring the long-term survival of porpoise in the region. Therefore, it is necessary
to outline porpoise conservation projects in deep areas and focus on efforts aiming to
alleviate conflict with humans.