Length-Weight Relationships of 52 Species from the South of Sicily (Central Mediterranean Sea)

Round 1

Reviewer 1 Report

GENERAL COMMENTS:

The manuscript "fishes-1660590" about Length-Weight Relationships (LWR) of several species from the northern sector of the Strait of Sicily (GSA 16) is of value and important to add new information to the knowledge base from the studied Mediterranean geographical sub area. The data provided by MS are of fundamental importance for future stock assessment studies, especially of those over exploited and sensitive species suffering of high fishing pressure. All statistical analyses are well developed and very functional for paper purposes, providing a very interesting comparison with past data from the same area. The sampling design is well-define, with a very large sample number recovering a wide time frame (from 2012 to 2019). The English is good, clear, and concise, also for readers not familiar with fisheries science. 

I have only some minor concerns mainly regarding Discussion and Conclusion chapters to improve the effectiveness and clearness of MS.

SPECIFIC COMMENTS:

Line 45: I suggest the authors to also add bibliography form Mediterranean Sea not only focused on LWR’s, but such also as those studies investigating trophic ecology, life history traits and biology of several species. Some examples are given here:

• D’Iglio, C., et al. "Biological and ecological aspects of the blackmouth catshark (Galeus melastomus, Rafinesque, 1810) in the southern Tyrrhenian Sea." Journal of Marine Science and Engineering 9.9 (2021): 967.
• Tiralongo, Francesco, Giuseppina Messina, and Bianca Maria Lombardo. "Biological Aspects of Juveniles of the Common Stingray, Dasyatis pastinaca (Linnaeus, 1758) (Elasmobranchii, Dasyatidae), from the Central Mediterranean Sea." Journal of Marine Science and Engineering 8.4 (2020): 269.
• Bayhan, Bahar, Tuncay Murat Sever, and E. R. T. A. N. Taşkavak. "Age, length-weight relationships and diet composition of scaldfish Arnoglossus laterna (Walbaum, 1792) (Pisces: Bothidae) in Izmir Bay (Aegean Sea)." Journal of Animal and Veterinary Advances 7.8 (2008): 924-929.

Line 96 (Table 1 caption): The sentence “In bold are the first references in the Strait of Sicily” is less clear. I strongly suggest rephrasing it. For example: “The species in bold type are those……”

Line 103–107: I suggest the authors to add the authorities in scientific names of the cited species (e.g., Mustelus punctulatus, Risso, 1827).

Line 117: As reported above, the authorities should be added to the scientific names. In addition, they have not been written in Italics. Fix them, please.

Line 126-129: What the authors mean with visual inspection? Please, explain it for a better text clarity.

Line 154: I strongly suggest the authors to increase the conclusion chapter adding future purposes and new applications for the research field (such as the comparison of LWR’s from different seasons in the same area or from different areas in the same season) to give more effectiveness to the chapter.

Author Response

Reviewer 1

Comments and Suggestions for Authors

GENERAL COMMENTS:

The manuscript "fishes-1660590" about Length-Weight Relationships (LWR) of several species from the northern sector of the Strait of Sicily (GSA 16) is of value and important to add new information to the knowledge base from the studied Mediterranean geographical sub area. The data provided by MS are of fundamental importance for future stock assessment studies, especially of those over exploited and sensitive species suffering of high fishing pressure. All statistical analyses are well developed and very functional for paper purposes, providing a very interesting comparison with past data from the same area. The sampling design is well-define, with a very large sample number recovering a wide time frame (from 2012 to 2019). The English is good, clear, and concise, also for readers not familiar with fisheries science. 

I have only some minor concerns mainly regarding Discussion and Conclusion chapters to improve the effectiveness and clearness of MS.

SPECIFIC COMMENTS:

Line 45: I suggest the authors to also add bibliography form Mediterranean Sea not only focused on LWR’s, but such also as those studies investigating trophic ecology, life history traits and biology of several species. Some examples are given here:

• D’Iglio, C., et al. "Biological and ecological aspects of the blackmouth catshark (Galeus melastomus, Rafinesque, 1810) in the southern Tyrrhenian Sea." Journal of Marine Science and Engineering 9.9 (2021): 967.
• Tiralongo, Francesco, Giuseppina Messina, and Bianca Maria Lombardo. "Biological Aspects of Juveniles of the Common Stingray, Dasyatis pastinaca (Linnaeus, 1758) (Elasmobranchii, Dasyatidae), from the Central Mediterranean Sea." Journal of Marine Science and Engineering 8.4 (2020): 269.
• Bayhan, Bahar, Tuncay Murat Sever, and E. R. T. A. N. Taşkavak. "Age, length-weight relationships and diet composition of scaldfish Arnoglossus laterna (Walbaum, 1792) (Pisces: Bothidae) in Izmir Bay (Aegean Sea)." Journal of Animal and Veterinary Advances 7.8 (2008): 924-929.

Authors: Thank you for your suggestion. However, the sentence that you mentioned is focused on LWRs aspects, so we added only Bayhan et al. (2008).

Line 96 (Table 1 caption): The sentence “In bold are the first references in the Strait of Sicily” is less clear. I strongly suggest rephrasing it. For example: “The species in bold type are those……”

Authors: We replaced the sentence as follow: “The species in bold type are those firstly reported in the Strait of Sicily”

Line 103–107: I suggest the authors to add the authorities in scientific names of the cited species (e.g., Mustelus punctulatus, Risso, 1827).

Authors: The authorities in scientific names of the cited species was added

Line 117: As reported above, the authorities should be added to the scientific names. In addition, they have not been written in Italics. Fix them, please.

Authors: Done

Line 126-129: What the authors mean with visual inspection? Please, explain it for a better text clarity.

Authors: To make more clear the sentence, we rephrased as follow:

“To the best of our knowledge, many studies compare the LWRs parameters without any statistical approach (i.e. through “visual inspection”) which often results in no reliability to detect the differences. Therefore, the methodology adopted in this study should be desirable in order to identify objectively differences in a and b parameters between LWRs. An evident example of the possible bias introduced by absence of a statistical approach is provided by the comparison of the growth parameters between the present study and Di Maio et al., (2020).”

Line 154: I strongly suggest the authors to increase the conclusion chapter adding future purposes and new applications for the research field (such as the comparison of LWR’s from different seasons in the same area or from different areas in the same season) to give more effectiveness to the chapter.

Authors: According to your suggestion we added this sentence: 

“In addition, the statistical approach here proposed could represent a useful tool to compare LWRs estimated from specimens of different size classes, seasons, or areas.”

Reviewer 2 Report

Length-weight relationships of 52 species from the South of Sicily (Central Mediterranean Sea)

Mansucript evaluation

Overall assessment

The paper offers LWR for 52 fish species. For all 52 species, there is Length-weight relationships estimates in the international science literature based on Fishbase and sealife base mainly. But for many of them, there is no study on Length-weight relationships in the study area. This is very important for the management tools of these species in the locality. Thus, the manuscript is in principle of interest to the readership around the world. However, there are corrections to be made on the spelling of scientific names and the choice of species to be retained in the end. Specific comments given below. Please follow the advice given.

Specific comments

Regarding species scientific name : The correct name is in bold and in parenthesis

For Crustaceans

Aritaemorpha foliacea (Aristaeomorpha foliacea)

For Bony fish

Boobs boops (Boops boops)

Pagellus erytrhinus (Pagellus erythrinus)

Sardina pilcharus (Sardina pilchardus)

Scomber scolias (Scomber colias)

Spicara flexousa (Spicara flexuosa)

Summary

The summary is too short in my opinion. The authors do not go back to the values of the LWR parameters found in the results part. Please give information about the calculated parameter values in summary.

Introduction

This part is well written, down to the point and clear

Material and methods

In principle well written. The only improvement that would be very usefull would be to indicate the mesh size of bottom trawls.

Results

Again, overall this chapter is fairly well written. However, we recommend to write some especies scientific names in italics on lines 117, 132, 133.

Discussion

This section needs to be rewritten because the authors focus too much on comparing results with other studies without discussing their own results. There are very low values of the b-parameter and the coefficient of determination. There are also different growth patterns between males and females of some species. All this should be discussed.

Conclusion are well writen

The paper can easily reach acceptable level, provided the comments above are responded to in an adequate manner.

Background information

 For Crustaceans

 Aritaeomorpha foliacea : the LWR parameters are interesting with a high R² for males and females. Keep this species in the list

Aristeus antennatus : The LWR has been studied for this species by several authors but not in this study area. But the R² of male is lower than 0.95 which is recommended and in addition the number of individuals is low (85) as well as the parameter b. Keep this species but it is necessary to combine males and females.

Nephrops norvegicus : this species is studied in Italy and the LWR parameters are interesting. keep the species on the list

Parapenaeus longirostris : There are several studies on LWR for this species, notably in Italy in the Strait of Sicily.  But b is less than 2.5 and the R² (0.93) of males is less than 0.95. It is necessary to keep the species but I prefer that you combine males and females.

Squilla mantis : This species was studied in the study area between 1994 and 1998. The value of the parameter b found in this study is lower than that found before, males and females separated. Also, the R² coefficient is low for this study, both sexes combined. In my opinion, this species should be eliminated from this work.

Eledone cirrhosa, Illex coindetii, Loligo Vulgaris, Octopus vulgaris, Sepia officinalis, Todarodes sagittatus : No information in the study area. For this species, the parameters of the LWR are interesting. Keep these species

Eledone moschata : I do not see any study on this species in the study area. The coefficient of determination is low (0.86). The species should be removed from the list.

Bony fish

Boops boops, Chelidonichthys lastoviza, Chelidonichthys lucerna,Diplodus annularis,Eutrigla gurnardus, Helicolenus dactylopterus, Lepidopus caudatus ,Lepidorhombus boscii,Lophius piscatorius, Micromesistius poutassou, Pagellus bogaraveo, Pagellus erythrinus, Pagrus pagrus et Trachurus trachurus : There are several studies on LWR of these species but not in the study area. In addition, the LWR parameters are interesting. Keep these species.

Mullus surmuletus : there are several studies on LWR of this species, two of them in Italy (“Andaloro, F., P. Arena and S.G. Prestipino, 1985. Contribution to the knowledge of the age, growth and feeding of hake Merluccius merluccius (L., 1758) in the Sicilian Channel. FAO Fish. Rep. 336:93-97 » et « Djabali, F., A. Mehailia, M. Koudil and B. Brahmi, 1993. Empirical equations for the estimation of natural mortality in Mediterranean teleosts. Naga ICLARM Q. 16(1):35-37. »). The parameters of the LWR are interesting. Keep the species

Pagellus acarne : there are several studies on LWR of this species, two of them in Italy (« Campillo, A., 1992. Les pêcheries françaises de Méditeranée: synthèse des connaissances. Institut Francais de Recherche pour l'Exploitation de la Mer, France. 206 p. » et « Andaloro, F., 1983. Résume des paramètres biologiques sur Pagellus acarne de la mer Tyrrhénéenne méridionale et de la mer lonienne septentrionale. FAO Fish. Rep. 266:89-92. »). The parameters of the LWR are interesting. Keep the species

Chelidonichthys cuculus, Citharus linguatula, Lophius budegassa, Phycis blennoides et Zeus faber : there are several studies on LWR of this species but not in the study area. In addition the LWR parameters are interesting for both males and females. Keep the species.

Scomber colias : very few studies on LWR of this species and the parameters are interesting. Keep this species.

Engraulis encrasicolus, Sardina pilchardus et Sardinella aurita : there are several studies on LWR of this species but not in the study area. In addition, the LWR parameters are interesting except the R² which is less than 0.95. This species should be removed from the list.

Spicara smaris : Few studies on LWR of this species of which 1 in Italy but in the Gulf of Castellammare in 2004. In addition the parameters are interesting except the R² is lower than 0.95. Species to eliminate from the list.

Trachurus mediterraneus : There are several studies on LWR of this species. Moreover the calculated parameters are interesting except the R² which is lower than 0.95 for males (0.94). Species to be retained but combine males and females.

Trisopterus capelanus : Two studies were reported by FishBase, on the LWR of this species. In addition, the LWR parameters are below 0.95 for both males and females. We keep this species but you have to combine the two sexes.

Merluccius merluccius : There are several studies on LWR of this species including two in Italy (“Andaloro, F., P. Arena and S.G. Prestipino, 1985. Contribution to the knowledge of the age, growth and feeding of hake Merluccius merluccius (L., 1758) in the Sicilian Channel. FAO Fish. Rep. 336:93-97 » et « Djabali, F., A. Mehailia, M. Koudil and B. Brahmi, 1993. Empirical equations for the estimation of natural mortality in Mediterranean teleosts. Naga ICLARM Q. 16(1):35-37. »). The LWR parameters are interesting. Keep the species.

Mullus barbatus : There are several studies on LWR of this species including one in Italy (“Levi, D., M.G. Andreoli and G.B. Giusto, 1993. An analysis based on trawl-survey data of the state of the `Italian' stock of Mullus barbatus in the Sicilian Channel, including management advice. Fish. Res. 17(3-4):334-341»). The LWR parameters are interesting for females but for males the R²<0.95. I think you need to combine the two sexes.

Spicara flexuosa : few studies on LWR of this species of which 5 in Italy but in the Gulf of Castellammare. In addition the parameters of LWR are interesting. The R² is lower than 0.95 for females. Species to be retained but with combination of males and females.

Cartilaginous fishes

Centrophorus granulosus, Chimaera monstrosa, Dalatias licha et Mustelus mustelus : There are some studies on LWR of this species but not in the study area. In addition the parameters of the LWR are interesting. Keep these species.

Etmopterus spinax, Galeus melastomus, Heptranchias perlo, Mustelus punctulatus et Scyliorhinus canicula : There are some studies on LWR of these species but not in the study area. In addition the LWR parameters are interesting for both males and females. Keep these species.

Squalus blainville : there are a few studies on LWR of this species including one in Italy (Cannizzaro, L., P. Rizzo, D. Levi and S. Gancitano, 1995. Age determination and growth of Squalus blainvillei (Risso, 1826). Fish. Res. 23(1-2):113-125) in the study area. In addition, the LWR parameters are interesting for both males and females. Keep the species

Author Response

Overall assessment

The paper offers LWR for 52 fish species. For all 52 species, there is Length-weight relationships estimates in the international science literature based on Fishbase and sealife base mainly. But for many of them, there is no study on Length-weight relationships in the study area. This is very important for the management tools of these species in the locality. Thus, the manuscript is in principle of interest to the readership around the world. However, there are corrections to be made on the spelling of scientific names and the choice of species to be retained in the end. Specific comments given below. Please follow the advice given.

Specific comments

Regarding species scientific name : The correct name is in bold and in parenthesis

 For Crustaceans

Aritaemorpha foliacea (Aristaeomorpha foliacea)

For Bony fish

Boobs boops (Boops boops)

Pagellus erytrhinus (Pagellus erythrinus)

Sardina pilcharus (Sardina pilchardus)

Scomber scolias (Scomber colias)

Spicara flexousa (Spicara flexuosa)

Summary

The summary is too short in my opinion. The authors do not go back to the values of the LWR parameters found in the results part. Please give information about the calculated parameter values in summary.

Authors: Thank you for your suggestion. We added the following sentence:

“Linear regressions were significant for all species (P<0.05) with R² values ranging from 0.86 to 0.99. The intercept (a) of LWRs ranged from 0.0003 to 0.4677 while, the slope (b) ranged from 2.1281 to 3.306.”

Introduction

This part is well written, down to the point and clear

Material and methods

In principle well written. The only improvement that would be very usefull would be to indicate the mesh size of bottom trawls.

Authors: According to your advice we added some information about the gear, as:

“The MEDITS survey was carried out in the summer and fall seasons using a GOC 73 trawl net characterized by a vertical opening ranging between 2.4 and 2.9 m and a 20-mm stretched mesh size at cod end (Fiorentini et al., 1999).”

 Results

Again, overall this chapter is fairly well written. However, we recommend to write some especies scientific names in italics on lines 117, 132, 133.

Authors: Done

Discussion

This section needs to be rewritten because the authors focus too much on comparing results with other studies without discussing their own results. There are very low values of the b-parameter and the coefficient of determination. There are also different growth patterns between males and females of some species. All this should be discussed.

Authors: Thanks to your suggestion we rephrased and added some sentence as follow:

“The comparison of the LWRs parameters estimated in the present study with others carried out in the Strait of Sicily highlighted that 14 LWRs represent the first references in the area. For the other 38 species, a comparison is provided in Appendix A. However, for Zeus faber , M. punctulatus, and Squalus blainville (Risso, 1827) this comparison was not carried out due to the lack of available literature. The growth types herein provided were in disagreement with Froese (2006) who reported that most of the fishes showed isometric growth.

The outcomes of T-TEST revealed that most of the LWRs (about 55%) reported in this study are in disagreement with those obtained previously by other Authors from the Strait of Sicily (Ragonese et al., 2004; CNR-IAMC, 2006; Cherif et al., 2008; Boudaya et al., 2008; Ragonese et al., 2009; Saidi et al., 2009; Ghailen et al., 2010; Gancitano et al., 2012; Marouani et al., 2012; Malagola, 2016; Mili et al., 2016; Miled-Fathalli et al., 2019; Di Maio et al., 2020).

The main differences were due to the estimations of b parameter which in some cases resulted lower than those reported in the literature. Probably, this might be linked to the sampling methodology, indeed in the present study, the data from MEDITS survey (fisheries independent) were analyzed while most of the compared studies used samples coming from trawling and/or small scale commercial fisheries (fisheries dependent). As matter of fact, the low selectivity of the gear used during the MEDITS survey allowed to sample representative size distribution of the population where the bulk of the catch is constituted by the juvenile fraction. In addition, since MEDITS survey investigates a wide and heterogeneous area, from inshore to offshore waters, another plausible source of bias may be due to the habitat type sampled: for example, younger individuals may be more prevalent at shallower depths than in deeper waters. In this regard, it is important to point out that for comparison purposes LWRs should be of similar size classes, the same units (e.g. grams and centimetres) (Bagenal and Tesch, 1978; Petrakis and Stergiou, 1995) or measurement type (e.g. TL and SL – standard length – or TW and eviscerated weight). In addition, LWRs are not constant throughout the year, varying seasonally in relation to many factors such as temperature, salinity, food (quantity, quality, and size), habitat, gonad development, sex, fishing time, fishing gear, and area (Pauly, 1984; Cannizzaro et al., 1991; Safran, 1992; Froese, 2006). Moreover,for cephalopods, the differences might be also related to the conservation modality. Indeed, as suggested by Massi (1993), the freezing process leads to an elongation of muscular tissue that may affect the measurement of ML. This could explain the different growth type found between sexes of the I. coindetii where the females and males showed negative and positive allometry, respectively.

To the best of our knowledge, many studies compare the LWRs parameters without any statistical approach (i.e. through “visual inspection”) which often results in no reliability to detect the differences. Therefore, the methodology adopted in this study should be desirable in order to identify objectively differences in a and b parameters between LWRs. An evident example of the possible bias introduced by absence of a statistical approach is provided by the comparison of the growth parameters between the present study and Di Maio et al., (2020). Indeed, although Di Maio et al., (2020) analyzing the size structure of spawning aggregation of Pagellus acarne (Risso, 1827) reports a value of b much higher than that reported in the present study, the T-Test does not detect significant differences. This methodology is very important in the shared stocks because it would allow obtaining unique and more accurate LWRs (calculated as the geometric mean of a and b) for the purpose of stock assessment.”

 Conclusion are well writen

The paper can easily reach acceptable level, provided the comments above are responded to in an adequate manner.

Authors: We salute the effort made. However, according to the statistical approach applied we would like to maintain the species listed in the table. Indeed, in the Material and Methods section we specified that: “The LWRs were shown by sex only when significant differences emerged by ANCOVA analysis, otherwise, they were provided as combined”. Therefore, the modification you suggested would be in contrast with the methodology applied by introducing subjectivity in the choice of the sex that should be analyzed. Concerning R², except for M. punctulatus, we believe that the values here estimated are quite high, although ideally should be as higher as possible, to explain the variation between length and weight.