Short Communication |
Corresponding author: Konstantinos Tsagarakis ( kontsag@hcmr.gr ) Academic editor: Rodolfo Reyes
© 2022 Nicholas Badouvas, Stylianos Somarakis, Konstantinos Tsagarakis.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Badouvas N, Somarakis S, Tsagarakis K (2022) Length–weight relations of 16 mesopelagic fishes (Actinopterygii: Myctophiformes and Stomiiformes) from the eastern Mediterranean Sea. Acta Ichthyologica et Piscatoria 52(4): 279-283. https://doi.org/10.3897/aiep.52.97577
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For many mesopelagic fishes, even basic knowledge regarding their biology is missing, greatly impeding their effective management. Here we present length–weight relations for 16 mesopelagic fishes sampled during research surveys in the Greek seas (eastern Mediterranean). The following species were studied: Benthosema glaciale (Reinhardt, 1837); Ceratoscopelus maderensis (Lowe, 1839); Diaphus holti Tåning, 1918; Diaphus metopoclampus (Cocco, 1829); Diaphus rafinesquii (Cocco, 1838); Hygophum benoiti (Cocco, 1838); Hygophum hygomii (Lütken, 1892); Lampanyctus crocodilus (Risso, 1810); Lobianchia dofleini (Zugmayer, 1911); Myctophum punctatum Rafinesque, 1810; Notoscopelus elongatus (Costa, 1844); Symbolophorus veranyi (Moreau, 1888) [Myctophidae]; Argyropelecus hemigymnus Cocco, 1829; Maurolicus muelleri (Gmelin, 1789) [Sternoptychidae]; Stomias boa (Risso, 1810); Chauliodus sloani Bloch et Schneider, 1801 [Stomiidae].With the exception of Diaphus holti and Symbolophorus veranyi, parameter b diverged significantly from isometry. Only two species (Benthosema glaciale and Chauliodus sloani) displayed negative allometry, while for the remaining 12 species a positive allometry was found, with the highest parameter b values estimated for Stomias boa and Diaphus rafinesquii. The median value of parameter b for all species was 3.236 and 50% of its values ranged from 3.173 to 3.323. Some variations of the parameter b were observed between our findings and other studies from the Atlantic and the western Mediterranean.
LWR, Mediterranean Sea, mesopelagic fish, micronekton, myctophids, twilight zone
Mesopelagic fishes constitute the most abundant group of vertebrate animals on the planet (
Mesopelagic fishes play an important ecological role, linking primary consumers to top predators (
Length–weight relations (LWRs) constitute essential knowledge for the application of fish stock assessment and management, necessary for the estimation of fish biomass from sampled length data and for ecological modeling and the estimation of growth in fish (
Fish samples were collected with pelagic trawls and midwater frames, during dedicated mesopelagic surveys as well as other routine acoustic surveys (
Length–weight relation parameters of 16 mesopelagic fish species sampled in Greek seas.
Species | a | 95%CI of a | b | 95%CI of b | n | r 2 | Length [cm] | Weight [g] | P-value | Growth type |
---|---|---|---|---|---|---|---|---|---|---|
Myctophidae | ||||||||||
Benthosema glaciale | 0.0106 | 0.0099–0.0115 | 2.916 | 2.863–2.969 | 691 | 0.944 | 2.0–7.4 | 0.055–2.925 | 0.002 | – allometry |
Ceratoscopelus maderensis | 0.0038 | 0.0036–0.0040 | 3.243 | 3.209–3.277 | 1318 | 0.964 | 1.9–8.9 | 0.02–4.709 | <0.001 | + allometry |
Diaphus holti | 0.0095 | 0.0081–0.0111 | 3.066 | 2.967–3.166 | 175 | 0.955 | 2.3–6.8 | 0.079–6.175 | 0.193 | isometry |
Diaphus metopoclampus | 0.0075 | 0.0055–0.0104 | 3.332 | 3.164–3.501 | 30 | 0.983 | 3.9–9.6 | 0.832–15.707 | <0.001 | + allometry |
Diaphus rafinesquii | 0.0050 | 0.0034–0.0072 | 3.521 | 3.302–3.740 | 41 | 0.965 | 1.7–9.4 | 0.028–11.49 | <0.001 | + allometry |
Hygophum benoiti | 0.0049 | 0.0046–0.0053 | 3.318 | 3.273–3.363 | 498 | 0.977 | 1.9–7.8 | 0.028–4.834 | <0.001 | + allometry |
Hygophum hygomii | 0.0058 | 0.0045–0.0075 | 3.281 | 3.131–3.432 | 78 | 0.961 | 3.3–8.1 | 0.292–5.63 | <0.001 | + allometry |
Lampanyctus crocodilus | 0.0023 | 0.0019–0.0027 | 3.314 | 3.214–3.415 | 244 | 0.946 | 2.7–17.0 | 0.025–40.312 | <0.001 | + allometry |
Lobianchia dofleini | 0.0067 | 0.0059–0.0076 | 3.228 | 3.141–3.314 | 194 | 0.966 | 2.7–6.0 | 0.138–2.003 | <0.001 | + allometry |
Myctophum punctatum | 0.0055 | 0.0051–0.0060 | 3.220 | 3.167–3.272 | 423 | 0.972 | 2.2–10.0 | 0.056–8.532 | <0.001 | + allometry |
Notoscopelus elongatus | 0.0043 | 0.0038–0.0049 | 3.189 | 3.118–3.261 | 146 | 0.982 | 2.9–12.5 | 0.128–13.561 | <0.001 | + allometry |
Symbolophorus veranyi | 0.0055 | 0.0039–0.0078 | 3.190 | 2.997–3.383 | 24 | 0.982 | 4.4–12.5 | 0.625–18.732 | 0.053 | isometry |
Sternoptychidae | ||||||||||
Argyropelecus hemigymnus | 0.0092 | 0.0086–0.0098 | 3.325 | 3.262–3.389 | 653 | 0.943 | 0.5–4.8 | 0.003–1.419 | <0.001 | + allometry |
Maurolicus muelleri | 0.0069 | 0.0068–0.0071 | 3.168 | 3.137–3.199 | 1437 | 0.966 | 1.9–6.3 | 0.049–2.65 | <0.001 | + allometry |
Stomiidae | ||||||||||
Stomias boa | 0.0004 | 0.0003–0.0005 | 3.523 | 3.394–3.653 | 67 | 0.980 | 5.5–25.3 | 0.253–43.026 | <0.001 | + allometry |
Chauliodus sloani | 0.0026 | 0.0021–0.0031 | 2.775 | 2.681–2.868 | 195 | 0.947 | 4.6–19.9 | 0.127–12.805 | <0.001 | – allometry |
Measured fish weight (W) [g] and length (TL) [cm] data were fitted to the power function
W = aTLb
where a and b are the intercept and slope of the power equation, respectively. Data were transformed, using their natural logarithmic values and adjusted to a linear regression model by application of the least squares method, as to estimate length–weight parameters a, b (
The estimated values of the parameter b were compared to values reported for the same species in similar studies from the western Mediterranean (
A total of 6214 fish individuals were used in the current length–weight analysis, but they were not equally distributed across species (Table
Considerable variations of the parameter b between our findings and other studies from the Atlantic and the western Mediterranean were observed, especially compared to those from the North Atlantic (Table
Values of parameter b and length ranges (LR) of mesopelagic fishes from other regions.
Species | North Atlantic |
Tropical Atlantic |
W. Mediterranean |
This study | ||||
---|---|---|---|---|---|---|---|---|
LR | b | LR | b | LR | b | LR | b | |
Argyropelecus hemigymnus | 18–40 | 2.750 | — | — | 13–34 | 3.032 | 5–48 | 3.325 |
Benthosema glaciale | 21–81 | 3.020 | 15–35 | 3.251 | 14–47 | 3.093 | 20–74 | 2.916 |
Ceratoscopelus maderensis | 27–85 | 3.172 | — | — | 16–64 | 3.191 | 19–89 | 3.243 |
Chauliodus sloani | 57–293 | 3.028 | — | — | — | — | 46–199 | 2.775 |
Diaphus holti | 10–69 | 3.350 | 11–50 | 3.006 | 25–53 | 3.360 | 23–68 | 3.066 |
Diaphus metopoclampus | 48–66 | 3.074 | 19–40 | 3.353 | — | — | 39–96 | 3.332 |
Diaphus rafinesquii | 28–84 | 3.433 | 11–70 | 2.850 | — | — | 17–94 | 3.521 |
Hygophum benoiti | 35–54 | 3.052 | — | — | 13–48 | 2.983 | 19–78 | 3.318 |
Hygophum hygomii | 44–48 | 3.052 | — | — | 39–58 | 3.136 | 33–81 | 3.281 |
Lampanyctus crocodilus | 38–183 | 3.240 | — | — | 22–128 | 3.345 | 27–170 | 3.314 |
Lobianchia dofleini | 28–62 | 2.609 | 13–30 | 3.130 | 21–43 | 3.338 | 27–60 | 3.228 |
Maurolicus muelleri | 27–60 | 3.296 | — | — | — | — | 19–63 | 3.168 |
Myctophum punctatum | 22–89 | 3.448 | 16–69 | 3.221 | 19–60 | 3.052 | 22–100 | 3.22 |
Notoscopelus elongatus | — | — | — | — | 30–107 | 3.248 | 29–125 | 3.189 |
Stomias boa | 70–205 | 3.184 | 53–153 | 3.042 | — | — | 55–253 | 3.523 |
Symbolophorus veranyi | 34–113 | 3.248 | — | — | 23–90 | 3.181 | 44–125 | 3.19 |
The current study attempted to assess length–weight equations for mesopelagic fish populations from the eastern Mediterranean Sea, setting the base for further biological studies necessary to support future management and research. Length–weight relations in the region have been examined in a localized context for only a few of the species considered here (e.g., Argyropelecus hemigymnus, Diaphus metopoclampus, Stomias boa; see
For the majority of fishes studied herein, b was within the expected range of 2.5 and 3.5, (
Some intraspecific differentiations of the allometric coefficient among the current study and similar works were identified, which were more diverse compared to estimates from the North Atlantic. These can be attributed to fish growth affected by internal and external triggers (such as diet and habitat temperature) (
This work was part of the project MesoBED “Mesopelagic fish: Biology, ecological role and distribution of a disregarded trophic link”, funded by the Hellenic Foundation for Research and Innovation and the General Secretariat of Research and Innovation (Greece) (Project No. 449).