the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
BOATSv2: New ecological and economic features improve simulations of High Seas catch and effort
Abstract. Climate change and industrial fishing have profound effects on marine ecosystems. Numerical models that capture key features of fish biomass dynamics and its interaction with fishing can help assess the biogeochemical and socio-economic consequences of these impacts. However, these models have significant biases and do not include many processes known to be relevant. Here we describe an updated version of the BiOeconomic mArine Trophic Size-spectrum (BOATS) model for global fish and fisheries studies. The model incorporates new ecological and economic features designed to ameliorate prior biases. Recent improvements include reduction of fish growth rates in iron-limited high-nutrient low-chlorophyll regions, and the ability to simulate fisheries management. Novel features described here include a separation of pelagic and demersal fish communities to provide an expanded representation of ecological diversity, and spatially variable fishing costs and catchability for more realistic fishing effort dynamics. We also introduce a new set of observational diagnostics designed to evaluate the model beyond the boundary of large marine ecosystems. Following a multi-step parameter selection, the updated BOATSv2 model shows comparable performance to the original model in coastal ecosystems, accurately simulating catch, biomass and fishing effort. The revised model provides a markedly improved representation of fisheries in the High Seas, largely correcting the biases of the original version, including excessive high-sea catches and too rapid deepening of fishing effort over time. The updated model code is available for simulating both historical and future scenarios.
- Preprint
(12015 KB) - Metadata XML
- BibTeX
- EndNote
Status: open (until 03 Aug 2024)
-
RC1: 'Comment on gmd-2024-26', Anonymous Referee #1, 12 Jun 2024
reply
Guiet et al. present recent developments in the BOATS global ecosystem model that improve ecological and economic processes to improve the fit of model results to biomass, catch and fishing effort data. BOATS is a size-spectrum global marine ecosystem model in which they mainly incorporated three new features: 1) a demersal guild in addition to the already existing pelagic guild, 2) a better representation of iron limitation and 3) a modified assumption of fish accessibility for fisheries including spatially variable fishing costs and catchability. The results show multiple improvements in the evaluation of various indicators, validating the necessity of these recent developments and the ability of the newly included mechanisms to reproduce the observed patterns.
I would like to emphasize the quality of the article, which is well written and overall clear on the description of the model's equations and assumptions. Well done to the authors, who have done a tremendous job in this respect. In addition, I very much appreciated the approach of developing and testing new mechanisms in the model by successive implementations. Thus, I think the article is timely as we need in marine modeling science to:
(i) Continue the development of existing models by including new robust mechanisms to understand and anticipate current and future human pressures on marine ecosystems
(ii) Have a clear description and documentation of model assumptions and equations to improve model usability, transparency and reproducibility. For these reasons, I fully support the authors' request to publish their paper in Geoscientific model development.
I also very much appreciated the ingenuity of the model parameterization and the selection of the best set of parameters: their approach could be more widely used for other marine ecosystem models in a context where model validation and calibration methods are still under discussion and development.
The structure of the document is unusual in that it includes a section on the sensitivity analysis of the model to certain parameters between the “Materials and methods” section and the results section and presents some of the results of the sensitivity analysis in this section. The need for this information to better appreciate the results makes it acceptable. Furthermore, the results and discussion are brought together in one, which I find very appropriate in this type of technical paper.
My main criticism concerns certain parts of the discussion. I found that some results for which the model does not perform well are never discussed, whereas a discussion accompanied by a hypothesis about potential missing processes in the model or experimental data could help validate the model and understand the gap that remains between the data and the model. One of the aims of the paper was to improve the representation of iron-limiting zones. Are the zones better represented in the iron-limited zone of Boatsv2? How do you explain the areas where the model performs less well? Similarly, when the model underperforms in v1 and v2, can you speculate on the reasons for this underperformance? Some global hypotheses are mentioned at the end of the discussion, but specific hypotheses for the highlighted area would be useful (North Atlantic, Eastern Pacific, etc.). Maybe other global ecosystem models (Apecosm, DBEM…) with different assumptions perform well in different region: it could be helpful to formalize. For more examples, see the detailed line-by-line commentary.
My second point concerns certain parameter settings. I noticed that some values/hypotheses were given without explanation. Even if they are assumed or derived empirically, I think it would be useful to specify them for greater clarity. See also the line-by-line commentary for more information.
Lastly, I found some minor typo error that needs to be corrected (see lines by lines)
To close, I wish to emphasize that I consider this research is already of great quality. My criticisms are simply intended to be helpful to developing/precising it.
L37: Add a source exploring multiple aspects of global fisheries dynamics
L39: the example of an ecosystem defined as HNLC could help non-specialists of this ecosystem to identify the type of ecosystem you are referring to.
L70: how is the vertical position of communities/captures estimated if the grid is 2D?
L80: First equation: The first term of the equation is a growth term, but it is negative. Is it the biomass that exceeds the group size threshold due to growth? If so, a sentence explaining this would be useful.
L86: If the minimum requirement is not met, this has no impact on mortality, why?
L95: "Primary production is equally distributed between groups". Why is this?
L103 and 104: The typography of the letter "phi" is different in this line and the next than in the rest of the text.
L107: Equation 3: same A0 as in the anabolism equation? If so, mention it either afterwards, or in the table of parameters.
L121-122: Do you think that using only the first 75 to estimate the temperature faced by the pelagic community is sufficient? Or could this be responsible for a bias in the representation of the community? If it is the second option, please discuss it
L136-138: I did not find the parameter em_o,k in the equation preceding (5). Explain why this information is given here or delete it.
L146: Since EK (t = 0) = 0, how do the dynamics of Ek begin?
L147: Table 1: Predator to prey mass ratio: this ratio is very high. Do you have a source that confirms this? How can the trophic scale parameter be interpreted biologically?
L157: "qk increases annually at a rate of 5%" : Where does this value come from? Is it realistic?
L171: Why is the reduction in primary production not enough to explain the change in fish growth? Do you have any arguments in favor of a change in trophic efficiency? How do they explain the mechanism in Galbraith et al?
L174: (NO-3 , in μM) is considered an indicator of iron limitation. Why is?
L199 and L278: What thickness is used to estimate Tbot? Does the thickness vary with bottom depth?
L208: How did you assume -0.8?
L221: Specify the activation energy of "growth and mortality" to help identify that these are 2 parameters.
L231: When fisheries target demersal species, do we agree that cost increases with distance from shore and depth? If so, I don't find this clear in the equation for the demersal community. If not, why not?
L322: 12 is not fixed in Table 1. Is this a reason not to recalibrate the trophic scale?
L324: (h ζ1) becomes (h and ζ1),
L355: "5 parameters (6 including the trophic scale)". Why do you make a distinction here?
L386: Figure 3: Acceptable range in addition to mean harvest could be useful ([70,150]x10^6) + Why is there an overall overestimation of pelagics?
Figure 4c: why the change in variability over time?
Table 3: why does v2-Bio* & Πβ seem to be the best model? *v2-Bio = v1 + αcorr + (Πψ : delete parenthesis
L389: These Australian LMEs: are they deep or iron-limited zones?
L445: How can mortality be negative? Perhaps more information on this term in the additional parameters table might help to understand where it comes from.
Figure 5a: How do you explain the increasing trend in the model for the 2 versions, which is not observed in the data? Is it linked to the exponential response to temperature? If so, it could be interesting to discuss what other temperature responses could have been used, and how they might impact the model.
L453: “Although the temperature dependence of mortality (ωa,λ) is not significantly different from the initial values, the optimized values suggest a stronger sensitivity of growth compared to mortality for the pelagic community (ωa,A −ωa,λ = +0.047 eV), and a stronger sensitivity of mortality for the demersal community (−0.082 eV).”. Is it supported by experimental studies of fish thermal responses?
L464: "indirectly allows larger asymptotic sizes (m∞) that are exposed to greater natural mortality; however, since m∞ is fixed". There's a contraction in that sentence, isn't there? If not, it needs to be explained differently.
L488: For ecological or economic reasons?
L495: Can you add a hypothesis about the reasons?
L540: What are the expectations in terms of the impact on carbon sequestration?
Table A1: n_k = 3. Why is this so? Is the model sensitive to this parameter?
Table A2: Temperature units. K or °C. Why use the 2 units?
Citation: https://doi.org/10.5194/gmd-2024-26-RC1
Model code and software
BOATSv2 and dataset for "BOATSv2: New ecological and economic features improve simulations of High Seas catch and effort" J. Guiet, D. Bianchi, K. Scherrer, R. Heneghan, E. Galbraith, and D. Carozza https://doi.org/10.5281/zenodo.11043334
Viewed
HTML | XML | Total | BibTeX | EndNote | |
---|---|---|---|---|---|
173 | 34 | 13 | 220 | 6 | 9 |
- HTML: 173
- PDF: 34
- XML: 13
- Total: 220
- BibTeX: 6
- EndNote: 9
Viewed (geographical distribution)
Country | # | Views | % |
---|
Total: | 0 |
HTML: | 0 |
PDF: | 0 |
XML: | 0 |
- 1