Spatial Ecology of the Population of Reef Manta Rays (Mobula alfredi) in New Caledonia Using Satellite Telemetry 2—Vertical Behaviour
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors- The sample size of 23 deployed tags with 19 successful transmissions is relatively modest for population-level analysis. The authors should justify the sample size calculation and discuss potential biases introduced by the high rate of premature tag detachment (only one tag completed the full 180-day deployment).​
- The study combines data from SPLASH10 and MiniPAT tags. The authors should provide a comparative analysis of data quality and resolution between these two tag types to ensure data consistency.​
- The definition of "deep dives" (>300 m) appears arbitrary. The authors should provide ecological or statistical justification for this threshold value and consider performing sensitivity analysis with alternative depth thresholds.​
- The statistical analysis section mentions various tests (ANOVA, t-tests, etc.) but lacks details on model assumptions checking. The authors should report how they verified assumptions of normality, homogeneity of variances, and independence of observations.​
- Figure 2 shows diel depth distribution but lacks statistical indicators. The authors should add error bars and significance markers to facilitate interpretation of the observed patterns.​rvations.​
- The dive profile analysis is based on only three individuals with recovered tags. The authors should explicitly acknowledge this limitation and discuss how this small subsample might affect the generalizability of the dive shape conclusions.​
- The interpretation of V-shaped dives as "exploratory behavior" requires more supporting evidence. The authors should consider alternative hypotheses (e.g., predator avoidance, thermoregulation) and discuss why exploratory behavior is the most plausible explanation.​
- The conservation implications are well articulated but lack specific recommendations. The authors should provide more concrete suggestions for how MPA design and management should be modified to account for the vertical dimension of manta ray habitat use.​
- The discussion appropriately highlights the foraging hypothesis but underrepresents alternative explanations for deep diving behavior. The authors should expand the discussion to include other potential functions.​
Author Response
Author’s general comment: We thank the reviewers for their careful evaluation and constructive comments. Below, we provide detailed point-by-point responses, highlighting the changes made to the manuscript to address each concern and to strengthen the clarity, robustness, and interpretation of our findings.
Comment 1: The sample size of 23 deployed tags with 19 successful transmissions is relatively modest for population-level analysis.
Response 1: We appreciate the reviewer's concern regarding the scope of our findings given the sample size. To accurately reflect our study's intent and acknowledge this limitation, we have systematically revised the wording throughout the Introduction, Methods and Discussion to avoid making population-level inferences.
Specifically, we replaced phrases that implied population-wide inference with language focusing on the individual-level. Modifications at the following lines:
- Abstract section: 16
- Introduction section: 121, 130
- Materials and Methods section: 170 - 172
- Discussion section: 438-440, 446-447
Comment 2: The authors should justify the sample size calculation and discuss potential biases introduced by the high rate of premature tag detachment (only one tag completed the full 180-day deployment).
Response 2: We thank the reviewer for this valuable comment. We have now included a detailed justification of the sample size and a discussion of potential biases introduced by premature tag detachment in a full paragraph in the revised manuscript.
Specifically, we clarify that the final sample size (N = 19) reflects the maximum feasible deployment effort given the substantial financial constraints associated with advanced biotelemetry tags. Although modest, this sample size remains comparable to, or greater than, those of published studies on Mobulid rays. Modifications at the following lines:
- Discussion section: 454 – 480
Comment 3: The study combines data from SPLASH10 and MiniPAT tags. The authors should provide a comparative analysis of data quality and resolution between these two tag types to ensure data consistency.
Response 3: We believe the reviewer is raising an important point. We have now included a detailed clarification in the Methods section describing the data comparability between SPLASH10 and MiniPAT tags.
Specifically, we explain that both tag types use comparable temperature, ambient light, and depth sensor technologies, offering equivalent depth resolution and accuracy. Modifications at the following lines:
- Materials and Methods: 203 – 215
Comment 4: The definition of "deep dives" (>300 m) appears arbitrary. The authors should provide ecological or statistical justification for this threshold value and consider performing sensitivity analysis with alternative depth thresholds.​
Response 4: We agree with the reviewer that this threshold may seem arbitrary as is and call for justification. In response, we have added text to the Methods section to clarify the rationale behind the 300 m threshold for “deep dives” provides both an empirical and functional justification, demonstrating that it is not arbitrary and is specifically chosen to characterize ecologically meaningful extreme dives.
Specifically, while statistical analyses (Change-Point Analysis and Gaussian Mixture Models) identified a shift in daily maximum depths around 120–130 m (see added Figure S1), we selected 300 m because it lies just below the minimum overall maximum depth recorded among all 19 tagged individuals (320 ±â€¯4 m). This depth therefore represents the shallowest boundary of the sustained, extreme deep-water habitat used by every manta ray in the study. It encompasses 10.1% of all daily maximum dives, isolating the rarest, deepest movements into the mesopelagic zone. Modifications at the following lines:
- Materials and Methods section: 228 - 238
Comment 5: The statistical analysis section mentions various tests (ANOVA, t-tests, etc.) but lacks details on model assumptions checking. The authors should report how they verified assumptions of normality, homogeneity of variances, and independence of observations.
Response 5: Indeed some details on assumption are lacking, we accordingly added a clarifying statement in the Methods section. Specifically, model assumptions for parametric tests (ANOVA, t-tests, Pearson’s correlation) were verified using Shapiro-Wilk tests for normality, Levene’s test for homogeneity of variances, and assessment of data collection methods (individual tags, discrete daily observations) for independence. Modifications at the following lines:
- Materials and Methods section: 269 - 272
Comment 6: Figure 2 shows diel depth distribution but lacks statistical indicators. The authors should add error bars and significance markers to facilitate interpretation of the observed patterns.
Response 6: Following the reviewer suggestion, Figure 2 has been modified with the addition of error bars and significance markers.
Comment 7: The dive profile analysis is based on only three individuals with recovered tags. The authors should explicitly acknowledge this limitation and discuss how this small subsample might affect the generalizability of the dive shape conclusions.
Response 7: We understand the concern of the reviewer and we addressed it by revising the Discussion to explicitly acknowledge the limitation associated with the small subsample of individuals used for detailed dive profile analysis. Modifications at the following lines:
- Discussion section: 481 - 488
Comment 8: The interpretation of V-shaped dives as "exploratory behavior" requires more supporting evidence. The authors should consider alternative hypotheses (e.g., predator avoidance, thermoregulation) and discuss why exploratory behavior is the most plausible explanation.
Response 8: We thank the reviewer for this insightful comment, which has helped us strengthen the clarity and depth of our interpretation. In response, we have expanded the discussion to include a more comprehensive evaluation of the potential functions underlying V-shaped dives, explicitly addressing alternative hypotheses such as predator avoidance and thermoregulation. Additionally, we have incorporated supplementary temperature-related data in the Results section to provide further context and empirical support for our interpretation. Modifications at the following lines:
- Results section: 351 - 355
- Discussion section: 509 - 579
Comment 9: The conservation implications are well articulated but lack specific recommendations. The authors should provide more concrete suggestions for how MPA design and management should be modified to account for the vertical dimension of manta ray habitat use.
Response 9: We agree that recommendations were lacking and we have expanded accordingly the final section of the Discussion to include specific suggestions for improving marine protected area (MPA) design and management in light of our findings. Modifications at the following lines:
- Discussion section: 660 - 667
Comment 10: The discussion appropriately highlights the foraging hypothesis but underrepresents alternative explanations for deep diving behavior. The authors should expand the discussion to include other potential functions.
Response 10: We thank the reviewer for this constructive comment. We believe this point is closely related to the previous remark (comment 8) regarding the interpretation of V-shaped dives. Accordingly, we have substantially revised the Discussion to incorporate a broader evaluation of alternative hypotheses, including predator avoidance, thermoregulation, and exploratory behaviour. These additions provide a more balanced interpretation of deep-diving functions and strengthen the overall argumentation. We are confident that these improvements address both this comment and the previous one.​
Reviewer 2 Report
Comments and Suggestions for AuthorsManuscript Number: fishes-3920332
Spatial ecology of the population of reef manta rays (mobula alfredi) in new Caledonia using satellite telemetry 2 – vertical behaviour
Journal – Fishes
This interesting paper provided details of the dive behaviour of reef manta rays (Mobula alfredi) in the waters of New Caledonia. This paper outlines the general use of the water column by reef manta rays, as well as detailed the dive behaviour of three individuals for which tags could be physically recovered and 100% of the data retrieved. This paper could do with some clarifications in terms of the number of dives analysed as the numbers vary throughout (n = 2870, n = 2869, n = 3012). Explicitly listing the number of dives analysed in each section would help clarify this and make it obvious if the full dataset is being discussed or the subset from the three individuals for which the tags were recovered.
The paper is relatively clear, concise and well structured. I have made various suggestions below to improve the clarity of the paper especially concerning the number of tagged individuals, which seems to vary throughout the paper. Given the variability in the dive behaviour of individual animals in such studies, exact replication of the study would be challenging, as for the majority of field studies. However, the analysis of similar data could be replicated with data similarly decoded using the Wildlife Computers’ platform. Conclusions drawn are consistent with the evidence presented.
Specific comments below:
Line 1 – Amend to – Spatial ecology of reef manta rays (Mobula alfredi) in New Caledonia using satellite telemetry to explore vertical behaviour
Line 15 – Amend to – reef manta ray (Mobula alfredi)
Line 22 – Here it says 22 tagged individuals but, in the methods (line 166, 170) it says 21 tagged with SPLASH10-F-321A PSAT tags plus two MiniPAT tags and an additional two tags deployed opportunistically at Touho. And 23 are listed at line 230. Please clarify this.
Line 18 – Amend to – with three tags providing sufficiently high-resolution information on dive behaviour to describe and quantify three-dimensional movements.
Line 41 – Amend to – (mesopelagic: 200 – 1,000 m; bathypelagic: > 1,000 m)
Line 37 – Amend to – …aggregation sites found at water body confluences and characterized by high fish abundance and diversity.
Line 47 – Amend to – populations are commonly observed near…
Line 49 to 50 – Amend to – Their horizontal movements have previously been investigated, revealing both…
Line 56 – Amend to – species’ precarious
Line 66 – Amend to – in feeding aggregations
Line 67 – Amend to – unregulated tourism
Line 78 – Amend to – demonstrated their effective use on terrestrial species, …
Line 84 – Amend to – have previously been gained through the use of biotelemetry, including PSAT tags.
Line 91 – Amend to – was among the first to extend the known depth range of M. alfredi, documenting a maximum dive depth of 432 m.
Line 95 – Amend to – on other Mobula spp.
Line 97 – Amend to – However, a study conducted …
Line 101 – Amend to – … remains unresolved, indicating a requirement for a more detailed investigation.
Line 95 – Amend to – … Mobula spp.
Line 104 – Amend to – … extreme dives (> 500 m) were…
Line 125 – Amend to – … to sustain these animals…
Line 126 – Amend – the present study aimed to…
Line 127 – First, we quantified the vertical habitat use of…
Line 129 – Amend to – Second, the study aimed to
Line 143 – Amend 2,000 meters to 2,000 m
Line 146 – Amend 2,000 meters to 2,000 m
Line 156 – Amend 15-meters to 15 m
Line 157 – Amend 30 meters to 30 m
Line 159 – Amend 20-meters to 20 m
Line 163 – Amend 15 meters to 15 m
Line 166 - 171 – See earlier point regarding 22 tags listed in the abstract. The way it reads suggests 25 tagged individuals, not 22. And 23 are listed at line 230. Please clarify this.
Line 189 – please provide details of what the cut-off percentage was for “incomplete” data that was excluded from the analysis.
Line 190 – mention here how many datasets were excluded (n = x many excluded datasets)
Line 197 – Amend under 300 m to below 300 m
Line 198 – Amend ± 5 m to ~ 5 m
Line 220 – 227 – please provide further details where possible here on what statistical packages were used in R for these statistical tests.
Line 207 – Amend 10 meters to 10 m
Line 209 – Amend V-skewed left to V-left skewed, throughout the manuscript
Line 209 – Amend V-skewed right to V-right skewed, throughout the manuscript
Line 239 – Amend to – …for unknown reasons…
Line 253 – n = 3012 – is this just the number of dives below 300 m? or the total of the number of dives analysed?
Line 263 – Amend – .05 to 0.05
Figure 2 – Amend to - per cent time-at-depth to Percentage of time-at-depth (%)
Line 265 – Amend to – Diel distribution of the time spent at maximum depth, among depth ranges, by reef manta rays…
Line 269 – Amend to – Manta rays were found in water temperatures averaging…
Line 269 – Amend to – …at temperatures…
Line 271 – Amend to – The maximum depth reached per day …
Line 272 – Amend – .05 to 0.05
Line 274 and 275 – Amend to – Maximum depths reached during the whole deployment were not different between …
Line 275 – Amend – .05 to 0.05
Line 276 – Amend – .001 to 0.001
Line 278 – Amend to – The proportion of dives below 300 m were significantly…
Line 279 – Amend – .001 to 0.001
Line 282 – Amend – .05 to 0.05
Line 283 – Amend to – …proportion of dives below 300 m …
Line 283 – Amend – .05 to 0.05
Line 284 – Amend to – …reef manta rays spent significantly more time within…
Line 285 – Amend – .001 to 0.001
Line 286 – Amend to – …between five and 50 m, during slightly longer periods at nighttime…
Line 286 – Amend – .001 to 0.001
Line 289 – Amend – .05 to 0.05
Line 293 – Amend to – …in more detail…
Line 295 – Amend – .001 to 0.001
Line 299 – Amend – .001 to 0.001
Line 304 – Amend – STT to SST
Line 311 – Amend – n= 2,869 to n = 2,869
Line 314 to 316 – what about V-left skewed dives? Percentages only sum to 79%, what about the remaining 21%? Also, the number of dives only sums to n = 2259 what about the remaining 610 dives?
Line 317 – Amend to – …were significantly the most observed behaviour…
Line 320 – Amend to – … V-shaped dives were consistently the most observed behavioural shape …
Line 321 – Amend V-skewed left to V-left skewed
Line 322 – Amend V-skewed right to V-right skewed
Figure 5 – y-axis – Amend per cent of dives to Percentage of dives (%)
Line 326 – Amend to – Distribution of the dive shapes per depth range, recorded for reef mantas…
Line 335 – Amend – here it says (n = 2,870) but at line 311 it says (n = 2,869)
Line 340 – Amend to – M4 reached maximum dive depths of 383 m and 385 m within a 28-day interval, with both exhibiting V-shapes profiles slightly skewed to the left, with a faster descent and slower ascent.
Line 344 – Amend to – M15 exhibited V-shaped dive profiles …
Line 345 – Amend to – For these dives, one was slightly right skewed, and the other exhibited an initial slow descent to 200 m followed by a steeper descent to the maximum depth (453 m or 458 m?) before ascending back to the surface.
Line 351 – Amend to – …trends in the diel partitioning of their vertical movements.
Line 352 – Amend – .001 to 0.001
Line 353 – Amend – .001 to 0.001
Line 353 to 354 – Amend to – …significant differences in vertical movements…
Line 354 – Amend – .05 to 0.05
Line 357 – Amend – .001 to 0.001
Line 359 – Amend – .01 to 0.01
Figure 7 – Amend V-skewed left to V-left skewed. Amend V-skewed right to V-right skewed. Place the * for the significant difference above the space between the black and white bars for V-shaped
Line 362 – Amend – here it says (n = 2,870) but at line 311 it says (n = 2,869)
Line 364 – Amend – .01 to 0.01
Line 366 – Amend to – Over a 24-hour period…
Figure 8 – Amend – (h) to (hr)
Line 371 – Amend to – Median swimming depth across the 24-hour period (10 min average), for all reef manta rays (Mobula alfredi) combined…
Line 373 – Amend – night-time to nighttime
Line 376 – Amend to – … the reef manta ray (Mobula alfredi), revealing…
Line 381 – Amend – under 300 metres to below 300 m
Line 385 – …documented in populations in other regions.
Line 390 – Amend to – finding in Lassauce et al. (2020)
Line 392 – Amend – N to n
Line 393 – Amend – N to n
Line 397 – Amend to – … associated with functions such as …
Line 418 – Amend – Mobula alfredi to M. alfredi.
Line 423 – Amend – animal to animals
Line 429 – Amend – Mobula alfredi to M. alfredi.
Line 431 – Amend to – … passively, manta rays can …
Line 441 – Amend to – … were also in the oceanic manta ray…
Line 447 – Amend – animal to animals’
Line 452 – Amend to – … alternative energy sources…
Line 454 – Amend to – … fact that very few manta…
Line 447 – Amend – condition to conditions
Line 483 – Amend to – availability of food resources
Line 484 – Amend to – … these resources might be scarce…
Line 488 and 489 – Amend to – … fisheries and human impacts remain relatively low.
Line 491 – Amend to – … taken at a local level…
Line 494 – Amend to – More significant sampling effort and long-term monitoring…
Line 495 – Amend to – … key habitats, and extending sampling to remote areas of the archipelago, such as isolated reefs may offer further insight into the species’ vertical diving behaviour.
Line 510 – Amend N = 14 to n = 14
Line 516 – Amend ranges to range
Line 518 – Amend to – differences in dive profiles of the deepest dives of reef manta rays…
Line 520 – Amend to – differences in the shape of dives (n = 2,869) performed by reef manta rays…
Line 521 – Italicize (Mobula alfredi)
Comments for author File: 
Comments.pdf
Suggestions regarding this have been made from throughout the manuscript.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for Authors- Further emphasize the limitations in the representativeness of the three tag recovery samples for the overall conclusions (lines 449–453）.
- Check for consistency in citation formatting (e.g., some references have inconsistent year formats).
Author Response
Comment 1: Further emphasize the limitations in the representativeness of the three tag recovery samples for the overall conclusions (lines 449–453）.
Response 1: We agree and have clarified that the high-resolution archival data from these three individuals, while valuable for characterizing fine-scale dive profiles and behaviors, may not fully capture the variability present across all tagged individuals. Modification in the following lines:
- Discussion section: 444 -452.
Comment 2: Check for consistency in citation formatting (e.g., some references have inconsistent year formats).
Response 2: We thanks the reviewer for spotting this inconsistency in the reference list. We made the modification accordingly. Modification in the following lines:
- Reference section: 811, 837, 842
