General comments

This paper investigates several oceanographic factors and one biological factor to try and explain the reasons for the breakdown of the positively correlated relationship between western rock lobster puerulus settlement and the strength of the Leeuwin Current off WA. The authors employ a multiple regression analysis to predict puerulus settlement, and also explore the influence of seasonal and inter-annual variations in the Leeuwin Current and Capes Current.

Given the high economic value placed on the western rock lobster fishery in WA, and given the past predictability of future catch by 3-4 years in advance has played a significant role in the sustainability of the fishery, this paper explores new drivers that would benefit scientists and managers in the fisheries and biological oceanography space. To arrive at these findings, the paper presents a lot of information, particularly around the oceanography, which I think could do with further refinement in order for the main takeaway messages to be clearer. These findings are presented more clearly in the concluding points of the paper, but not so much in the results/discussion section.

There is a lot of information presented in this paper which makes it quite tricky to digest in some parts. In particular, the high number of predictor variables and oceanographic patterns explored for each station, on top of splitting the data temporally and spatially. It’s potentially borderline too much for one paper, but I understand the complexity of oceanographic and biological patterns and the need to examine the extent of variables chosen in this paper.

In general, some sentences are quite long and could benefit from a grammar check and the addition of commas. I strongly recommend another round of editing on the document. Clear, concise and grammatically correct sentences will help with the digestion of a vast amount of information.

Specific comments

Abstract

Summarises the paper well

Introduction

Overall, I think the information presented in the introduction is relevant but could be more streamlined, have a clearer flow and avoid repetition. The aim is also mentioned twice but with different wording, so I suggest to just provide it once in the last paragraph of the intro

Line 36: ‘Puerulus settlement has subsequently recovered, but despite extensive research’, can you give a quick indication of where the extensive research focused e.g., in the oceanographic space, biology space

Figure 1: consider whether should be in the methods section, given the caption is also methods related.

Line 96: Could this sentence ‘Prior to current study, research on the 2008/09 decline had included an examination of overfishing of the spawning stock (de Lestang et al., 2015) and whether conditions of survival were no longer met in the early pelagic life stages (Säwström et al., 2014)’ be moved up to plug the missing info mentioned in comment above Line 36?

Study region

Line 150: Sentence starting with ‘An increasing’ needs rewording, sounds confusing. Is ‘replicated’ the right word?

Methods

Line 158: ‘The fishery-wide standardized puerulus index, PI, is calculated based on the seasonal (May – April) mean puerulus settlement numbers from all 8 sites, then summed to obtain an annual index (Kolbusz et al., 2021)’ repetition. Already mentioned in Intro. Pick one or the other. Suggest keep in methods.

Line 236: Can you clarify this sentence ‘Models containing variable combinations with correlations > 0.4 were excluded, to eliminate potential problems with collinearity and overfitting (Graham 2003)’? Are you referring to predictor variable combinations? If so, isn’t the cut off 0.4 correlation between two predictor variable quite low? Typically it is set at 0.7 or 0.8 before you would start to exclude correlating predictor variables. But I can see further down you mention  >0.8. So perhaps just needs clarifying a bit more.  

Table 1: ‘Predictor variables and metrics’

Line 267: expand on what you mean by ‘hiatus’ and during what years?

Results/discussion

Line 274: you say ‘time-series patterns of the spatial and temporal variability of the physical environment experienced by P. cygnus larvae between 2000 and 2017’, but then start of section 4.1 talking about variability in puerulus settlement. So summary wording around this section (from line 274) needs to be revised to reflect content accurately.

Line 275: ‘(2) exploring correlation of oceanographic conditions with multiple regression analysis’. Is that the right wording? Would ‘correlations between predictor variables and puerulus settlement’ be more accurate?

Line 309: these sentences sounds contradictory: ‘The CC strength was highly variable between latitudes. Over the initial months of the current forming (Figure 7a) it is, on average, strongest at 30⁰ S. The CC displayed a roughly a similar pattern across all latitudes with less variability in current at 27⁰ S where it is weakest (Figure 7).’

Line 324: is it meant to say ‘decreased at 31S and 27S?’ Not 29S?

Line 412: suggest putting sentence ‘From our analysis we have not defined directionality and size of the LC eddies, but it is an important consideration that would require further modelling, outside the scope of the current study’ in method section as I was expecting you to mention anticyclonic or cyclonic eddies somewhere. It is an important consideration, and one I would have expected to see in the modelling/analysis given the detail of the other predictor variables used, and the potential impacts of the eddy types on body condition of larvae.

Line 457: what do you mean by ‘due to memory in the system adjusting’?

Line 466: is ‘communicated’ the right choice of word?

Line 487: ‘A shift in mean LC and CC conditions’ – clarify what conditions, speed, direction?

Technical corrections

Line 33: reword sentence to say ‘During the 2008 and 2009 settlement seasons (May - April) there was an unexpected settlement failure, given the strong Leeuwin Current over those years.’ In some cases throughout the document, you break up the sentence in a way that it doesn’t flow. Such as the above example.

Line 52: missing bracket. Plus sentence needs clarification e.g.: ‘The onshore transport and movement of puerulus across the continental shelf occurs mainly during August – January (late austral winter-summer), where settlement occurs in shallow areas of generally less than 5 metres depth’

Line 61: ‘since the majority’

Line 96: put month range for ‘second half of the season’ as did for first half of season

Line 105: ‘effects are at play For example’ missing full stop

Line 135: join string of references ’Wijeratne et al., 2018) (Smith et al. 1991…’

Line 148: ‘Eddies in LC are’ – ‘from the’ or ‘in the’

Line 159: switch between 8 sites and eight sites – consistency. Spell out if between 1-10.   

Line 220. Missing full stop at end of sentence

Line 270: why is ‘(Fremantle Mean Sea Level; Southern Oscillation Index)’ needed in brackets when already defined in same sentence?

Line 320: add °S after 33 as well

Lin 324: Another example of a sentence that needs better grammar: ‘In particular at 27°S on average

325 offshore transport was possibly due to more mixing and a wider continental shelf and increased mixing around Shark Bay and with the contribution of the Ningaloo Current likely playing a role (Woo and Pattiaratchi, 2008).’

Line 362: Another example of a sentence that needs better grammar: ‘However, the South Indian Counter Current flows eastward within the defined southern ‘box’ of KE, one would expect if this had such an influence that it would be true for all sites and not only within the early portion of the season (Wijeratne et al., 2018).’

Line 369: ‘for survival. This may explain’

Line 382: ‘but these trends becomes’ – become

Line 395: positive not position

Line 405: most not model

Line :419: (early or late, Figures 10, 9a and b)

Line: 422: fix ‘failure of 2008 and 201109’

Line 453: ‘fluctuated in a similar’

Line 510: Grammar: ‘An increased LC while puerulus are crossing the shelf may transport them southward and either settling closer to Cape Mentelle or wash them too far offshore to return’

Line 514: however this is beyond the scope

GENERAL COMMENTS

This paper explores the influence of factors associated with the Leeuwin current (LC) and the Capes current (CC) in explaining the breakdown of the historical relationship between recruitment of western rock lobster recruitment and the strength of the LC. To do so, they use a series of GAMs to model the best predictors of the settlement index at 8 sites and pars of the settlement season. The predictors explored are associated with oceanographic parameters describing the LC and CC, as well as cross shelf transport and a breeding stock index.

Overall, this is a useful paper that will be useful to rock lobster fishery managers. However, because the paper is exploratory, there is a lot of complex information and the main goals and takeaway point a get lost. The work itself appears to be solid, but is presented a little unclearly. I think a revision paying close attention to outlining specific goals in the introduction and structuring the paper around those goals could help. I also recommend revision for both grammar and to improve readability by making the writing more concise.

SPECIFIC COMMENTS

1. The introduction does a nice job of introducing the study system, but it does not introduce the impetus for the hypotheses well. For instance, why did the authors choose to explore specifically KE and EKE (lines 116-117). This is discussed in the results/discussion, but is not introduced. I want to be convinced that these are useful parameters to explore—not simply that they are ones that can be examined. This could be a way to set up more specific aims of the paper. Similarly, the authors have chosen to report a combined results and discussion section. I actually think the paper may be more clear if these are separate—there were many paragraph in this section that were simply reporting of results with no discussion. This made the main points of the discussion get a little lost.
2. Figure 2: a set of photos would be better. Additionally, the figure does not capture what is written in the text well. For example, the 9 stages are not noted and the timelines indicated on the figure and in the text (line 51) do not match well. These also do not match the methods well (ex: line 182/183).
3. Line 207- 208: I am unclear what you mean by the temperature of the top 100m of the assumed phyllosoma distribution. Does this mean the top 100 m of the water column (and that is the assumed distribution), or some other depth that is the top 100 m of their deeper distribution. Also, is there a reference for this assumed distribution or is this your assumption?
4. Section 3.4 My understanding is that the authors fitted 16 different GAMs. I would call this section “generalized additive modeling” or something similar instead. It is also not clear what the response variables in the 16 models actually are though. The results (fig 10) say “settlement”—I assume this is the purlieus index? (it is clear that this is both for the late and early season and all sites in the figure and the methods). Similarly, I am confused by why the GAMs were limited to linear relationships (line 238). Why use GAMs then? Can you please clarify?
5. Figure 5: this could be labeled more clearly. First, the x axis appears to be year, not season. Second, it would be more clear to have they axis of b labeled as “offshore temp (top 100 m). In the figure heading, I am unclear about how that season is defined as January – December. Isn’t that the whole year? Finally, I suggest labeling the y axis for c as “Spawning Season Temp (bottom).”
   1. Fig 5-9: I also think it would be useful to shade the years of low PI as in other figures.
6. While I quite like Figure 10, you need to have the details of the models and model selection proecss in an appendix at the very least. 

TECHNICAL COMMENTS

• Figure 1a Legend—third sentence is incomplete
• The entire manuscript should be edited for comma rules to improve readability. I saw comma mistakes throughout that made sentences hard to read.
• Extraneous parentheses in line 135
• Table 1: I don’t understand the coding in the hypothesized relationship column.
• Fig 4; the abbreviations (ABR, PBK, etc) should be defined in the figure legend. Are these arranged by latitude? This could be included as well.
• Line 303-305 is an odd sentence structure
• Figure 6-8 : Here the x axes are year, not season
• You may consider combining Figures 6 & 7 into one figure since they are discussed together. I found I kept looking at the wrong figure and combing them into one with clear labeling and different coloring may help.
• Line 239: extra “An”
• Line 344: that instead of which. This sentence is also oddly phrased and should be broken into two sentences.
• Fig 11 legend. Delete the extraneous “model”
• Line 412: extraneous period at the end of the sentence
• Line 422: I assume 201109 should be 2009
• Line 470: “that” instead of “which”