To investigate the relationship between diving (DR), tortuosity ( R ? ) and foraging opportunity, the proportion of time seafood were present in video (pfish, all species pooled due to rarity of individual species, which included known or potential prey based on stomach contents; Grainger et al., 2020; see Supplementary Video 2) was quantified as a proxy for prey availability over 15 min windows. Several other non-prey/miscellaneous objects were also observed (e.g., jellyfish, starfish, and detached kelp), but excluded from analysis due to their rarity (absent in >90% of summary windows for most individuals).
fish were investigated by fitting several candidate zero-inflated beta mixed models (ZIBMM, accommodating zeros where fish were absent; Douma and Weedon, 2019) using the “glmmTMB” package, with R ? , DR or DR + R ? as predictors, an individual random intercept or intercept + slope (as for LMMs above), and an Ornstein-Uhlenbeck (OU) temporal correlation structure (“ou” function) for irregularly spaced time series (night-time hours between 4 pm and 7 am excluded from analysis; Brooks et al., 2017). Fixed, random effects and correlation structures were specified for both the conditional and zero-inflated components of each model. The favored model was determined using AICc comparisons as above. Convergence failed in several models unless the OU correlation was removed from the conditional and/or zero-inflated component, however this produced correlated residuals and did not improve the AICc. Thus, model selection only considered converged models including the OU structure.
Total Movements and you will Displacement Shortly after Release
Cats cams was implemented into the 7 light sharks (4 guys and you may 4 lady, 168–258 cm Fl) to possess 9.7–136.2 h, promoting 258.8 h away from logger analysis (indicate ± SD = thirty two.4 ± 25.step one h, assortment = nine.7–87.cuatro h) and you may 81.6 h off movies (imply ± SD = 10.dos ± cuatro.2 h, range = 5.0–15.step three h, anywhere between 7 have always been and you can cuatro pm daily; Desk 1). The sharks went overseas immediately after release (?10–30 km away from shore) having a suggest ± SD NLD range on marking area out-of forty-five.dos ± 61.5 km and you will NLD rate of just one.step 1 ± 0.4 kilometres h –step one (Table step one and you will Shape step one). Really sharks gone southern area-eastern of your tagging place (suggest ± SD NLD hit = 146.six ± 36.7°, Dining table 1 and you may Profile step one). That it instantaneous blog post-release path is actually substantiated because of the videos together with oscillatory diving regarding sharks www.datingranking.net/fr/rencontres-asexuees within facial skin and you may seabed, with the limitation breadth out-of successive dives (approximating seabed depth) growing through to the ?40–sixty yards depth profile (imply ± SD time for you to visited 40 meters figure = 5.6 ± step 3.cuatro h, variety 2.3–eleven.step three h, Contour 4). You to shark with a lengthier deployment period (s370w) travelled 195.dos km southward during the 5.1 week, with a comparable NLD rates to many other individuals (Table 1 and you may Contour 1B). Tailbeat analyses conveyed cases of gliding (no tailbeat), mostly through the diving descents (Data step three, cuatro and you will Additional Movies step 1). Whales hit a suggest ± SD limit breadth of 69.six ± 25.dos m (range 41.5–118.4 yards), and usually stayed for the oceans > 40 m depth immediately after the first overseas direction (Contour cuatro). Following the an initial plunge phase, some individuals tended to swimming peak throughout the day and you can dive even more in the evening (Profile 4). Yet not, shark s378w presented a different sort of trend, leftover nearer to coast (even after an identical deployment length to many other some body, Profile step one and you can Table step one) and you can diving constantly (Profile cuatro). Videos investigation indicated that sharks swam mostly during the seabed (indicate ± SD, 39.8 ± twenty-five.2% of time) otherwise surface (37.step 1 ± twenty four.8%) and spent a shorter time in the water line (23.step one ± fifteen.6%). Mud was the best substratum (38.9 ± 26.0% out of total analyzed videos), having reasonable access to other habitats (Supplementary Figures 2, 4).
Leave a Reply