Reef manta beam (M. alfredi) sightings and you may related hitchhiker varieties (1987–2019)
Spatial type regarding presence quite apparently observed hitchhiker kinds that have M. alfredi (adult and you can teenager Age. naucrates) was indeed investigated by mapping the fresh new percentage of sightings at each site (labeled by website function) where hitchhiker species try establish (final number out-of sightings where hitchhikers were seen / final number away from sightings during the webpages) into the ArcGIS 10.eight. Any internet that have a maximum of nine or a lot fewer sightings (213 internet sites) were excluded to attenuate this new bias a reduced level of sightings may have towards the research.
Temporary adaptation from the visibility away from adult and you may teenager E. naucrates having M. alfredi are examined having fun with month-to-month day show. That it show included that time to the best quantity of sightings (2008–2019) to include the ideal months where in order to visualise trend (i.e., seasonality). The fresh new month-to-month total number away from sightings have been remedied to own questionnaire effort of the figuring the new mean monthly level of manta rays observed for every questionnaire (monthly overall manta ray sightings / monthly final amount away from surveys).
Generalised linear blended models.
Logistic generalised linear mixed models (GLMM) using R v4.0.0 were used to investigate relationships between the presence of the most frequently observed hitchhiker species (adult and juvenile E. naucrates, G. speciosus, and Lutjanus bohar) with M. alfredi and four explanatory variables: sex with pregnancy status, maturity status, site function (determined by the predominant behaviour observed at the site ), and seasonality (NE or SW Monsoon). Due to the low number of recorded associations between M. alfredi and most of the hitchhiker species, only those with sufficient data were included in the GLMM analysis. The same model was used for Remora remora (the most frequently observed hitchhiker species with M. birostris), but without site function, and sex was classified only as male or female as pregnancies were only observed during four sightings. Each GLMM was dating sites for Middle Eastern Sites people fitted with a logit link function to the binary response of hitchhiker species presence (1) and absence (0) using the ‘lme4′ R package . Each model contained the manta-ID as a random intercept to account for any temporal autocorrelation arising from individual rays being repeatedly observed . To compare the relative goodness-of-fit, GLMM models without random effects (GLM) were tested. To reliably estimate the parameters, categories of variables with levels observed equal to or less than five times were removed. For example, under the category behavioural activity, the level ‘breaching’ was observed on less than five occasions, so was removed from analysis. The most informative explanatory variables were identified by firstly testing GLMM models with all combinations of explanatory variables. The variance inflation factor (VIF) was used to test models for multicollinearity; the maximum VIF was <1.5. Model performance was assessed using corrected Akaike information criterion (AICc) test statistic using the ‘MuMin' R package , and the DHARMa R package was used to check the model residuals were normally distributed. The highest-ranking models (with the lowest AICc value, S1 Table) for each hitchhiker species were then interpreted in terms of odds ratios (ORs) (the likelihood of the presence of the hitchhiker species in comparison with the reference category). Any models with ?AICc <2 were considered in interpretation of the highest-ranking model . The significance of each explanatory variable was determined by the 95% confidence interval (CI) of OR, whereby a narrower CI indicates a more precise estimation while, in comparison, a wider CI which had a greater uncertainty. A CI that crossed one is considered non-significant. Any ORs with p > 0.05 are not reported.
Overall performance
A total of 4901 Meters. alfredi have been privately known [male = 2442 (50%), women = 2459 (50%)] through the a maximum of 72912 sightings, from which 44071 (60%) were of women [mature = 25700 (58%), juvenile = 18371 (42%)] and 28841 (40%) was in fact men [adult = 25968 (90%), subadult = 1443 (5%), teenager = 1430 (5%)]. The sightings happened across 353 websites, where 95 (27%) were clean channels [sightings = 24034 (33%)], 53 (15%) was driving parts [sightings = 129 (0%)], and you can 205 (58%) serving parts [sightings = 48749 (67%)].