ORIGINAL RESEARCH published: 27 July 2021 doi: 10.3389/fmars.2021.625422 Length-Weight Relationship of 60 Fish Species From the Eastern Mediterranean Sea, Egypt (GFCM-GSA 26) Sahar F. Mehanna 1* and Alam Eldeen Farouk 2 1 Fish Population Dynamics Lab, National Institute of Oceanography and Fisheries, Suez, Egypt, 2 Central Laboratory for Aquaculture Research, Abbassa, Egypt Edited by: Les Watling, University of Hawai‘i at Mānoa, United States Reviewed by: Isabella Bitetto, COISPA Tecnologia and Ricerca, Italy Myriam Khalfallah, University of British Columbia, Canada *Correspondence: Sahar F. Mehanna sahar_mehanna@yahoo.com Specialty section: This article was submitted to Marine Biology, a section of the journal Frontiers in Marine Science Received: 06 November 2020 Accepted: 24 June 2021 Published: 27 July 2021 Citation: Mehanna SF and Farouk AE (2021) Length-Weight Relationship of 60 Fish Species From the Eastern Mediterranean Sea, Egypt (GFCM-GSA 26). Front. Mar. Sci. 8:625422. doi: 10.3389/fmars.2021.625422 Length-weight relationships (LWRs) are described for 60 important pelagic and demersal fish species caught during fishing surveys using trawl fishing gear in the Eastern Mediterranean, Egypt (General Fisheries Commission for the Mediterranean GFCM-GSA 26), and the data collected from the commercial catch during the period from July 2017 to December 2018. Linear regression using natural logarithmic transformation data was performed to calculate the a and b coefficients of LWR for 60 fish populations covering 23 families, 43 genera, and 60 species inhabiting GSA 26. The samples size, minimum and maximum lengths and weights with their mean and SD, LWR constants, ± 95% confidence interval (CI) of b, r 2 , and the type of growth were calculated and summarized. This study reports the first LWR estimates for 35 species in the Egyptian waters of the Mediterranean Sea. Keywords: GFCM-GSA26, Mediterranean Sea, length-weight relationship, growth, Egypt INTRODUCTION Egyptian fisheries contribute a great deal to food security and therefore play a very important role in the economy of the country. In Egypt, there are three main fish resources: marine fisheries (the Mediterranean and the Red Seas), inland fisheries (lakes and the Nile River), and aquaculture. Fisheries and aquaculture supplied Egypt with 1.9 million tons of fish in 2018, mostly used for domestic consumption. Egypt has two separate Exclusive Economic Zones (EEZs): one of 169,125 km2 in the Mediterranean with a shelf area of 31,017 km2 , and the other of 91,279 km2 in the Red Sea with a shelf area of 23,180 km2 a . The Egyptian marine fisheries yield up to 100,000 tons of a large variety of commercial fish, Mollusca and Crustacean species (62,000 and 38,000 tons from the Mediterranean and the Red Seas, respectively). The Egyptian Mediterranean coast is divided into four main fishing grounds namely; the Western region (Alexandria and El-Mex, Abu-Qir, Rosetta, El-Maadiya, and Mersa Matrouh), the Eastern region (Port Said and El-Arish), the Damietta region, and the Nile Delta region (General Authority for Fish Resources Development, 2018). a www.seaaroundus.org Frontiers in Marine Science | www.frontiersin.org 1 July 2021 | Volume 8 | Article 625422 Mehanna and Farouk LWR of 60 Species From GFCM-GSA 26 FIGURE 1 | General Fisheries Commission of the Mediterranean sub-areas (GFCM GSAs). FIGURE 2 | Eastern Mediterranean, Egypt (GSA 26) showing the main landing sites. Demersal fishes are important species landed by the industrial and the artisanal fleet from the Egyptian coastal waters of the Mediterranean Sea constituting about 33% of total fish yield in Egypt (Statistical fish book, 1991–2018). This is equivalent to about Egyptian 1,500 million Egyptian pound per year (about or ≈ 100 million US$). While the small and large pelagics and semipelagics constitute about 67% of the total fish yield from the Egyptian Mediterranean, achieving about 2,000 million LE (about or ≈ 133 million US$) (Mehanna, 2019a). To estimate the biomass of different fish populations, it is necessary to know the length-weight relationships (LWRs) of the studied species. LWR is of great importance in fish stock assessments (Garcia et al., 1989; Haimovici and Velasco, 2000). Length and weight measurements in conjunction with age data can give information on the stock composition, age at maturity, life span, mortality, growth, and production (Diaz et al., 2000; Frota et al., 2004; Froese, 2006). For fish, size Frontiers in Marine Science | www.frontiersin.org is representative of age, diet, and other physiological and environmental factors. Theoretically, size is representative of age because fishes never cease to grow in size and size is dependent on external factors, not the opposite. Consequently, variability in size has important implications for diverse aspects of fisheries science and population dynamics (Erzini, 1994). Length-weight regressions have been used frequently to estimate weight from length because direct weight measurements can be time-consuming in the field (Sinovcic et al., 2004). Generally, LWR of fish is used to estimate the wellbeing of fish, its biomass from length observation, the conversion of growth in length equations to growth in weight, and it is also useful for between-region comparisons of the life history of species (Pauly, 1993; Goncalves et al., 1997; Binohlan and Pauly, 1998; Stergiou and Moutopoulos, 2001). In this study, the LWRs were estimated for 60 demersal and pelagic fish species that are the most dominant and commercial 2 July 2021 | Volume 8 | Article 625422 Mehanna and Farouk LWR of 60 Species From GFCM-GSA 26 TABLE 1 | Common fish species in the GSA 26, including family name, the scientific name of species, total number, length and weight range, and the mean ± SD. Family Sparidae Carangidae Serranidae Triglidae Centracanthidae Solidae Bothidae Clupeidae Nemipteridae Scientific name No. Length range (cm) Weight range (g) Min Max Mean Min Max Mean 220.9 ± 141.3 Sparus aurata 659 10 35.6 23.5 ± 5.7 16 660 Pagellus erythrinus 1,326 4.2 30.1 15.1 ± 5.5 2 400 69.7 ± 78.2 P. acarne 378 9.1 24 15.5 ± 3.4 11 160 38.3 ± 24.6 Boops boops 815 9 27 16.5 ± 3.4 7 190 46.7 ± 26.3 Lithognathus mormyrus 654 8 22.9 15.4 ± 2.2 8 140 49.5 ± 20.4 Diplodus annularis 444 11 28 18.6 ± 3.5 22 325 96.9 ± 60.2 D. sargus 350 12 38 19.7 ± 3.3 23 850 109.8 ± 61.6 D. vulgaris 473 9.5 25 14.2 ± 1.8 10 250 85.8 ± 31.1 D. cervinus hottentotus 200 12 30 18.1 ± 2.5 25 400 99.1 ± 53.3 Pagrus pagrus 300 15 35 23.3 ± 4.5 35 650 203.3 ± 120.6 Dentex dentex 450 16 51 26.2 ± ± 1.7 45 1,750 290.8 ± 110.1 Trachurus trachurus 540 10 27 16.7 ± 3.7 11 170 47.2 ± 31.7 T. mediterraneus 480 10 26.5 16.2 ± 3.5 10 160 41.1 ± 18.9 Epinephelus aenus 98 35 100 50.2 ± 5.8 700 11,000 1550.3 ± 221.8 Serranus hepatus 389 5 18.2 12.7 ± 3.9 3.8 65 29.4 ± 21.5 Serranus cabrilla 321 7 23 15.6 ± 2.8 8 135 58.9 ± 25.8 Chelidonichthys lucerna 565 8 29 17.3 ± 3.1 7.9 250 52.7 ± 28.5 Trigloporus lastovisa 632 6 25 14.4 ± 2.7 2.8 160 43.2 ± 20.6 Lepidotrigla dieuzeidei 480 7 17.9 13.1 ± 1.9 3.9 75 28.5 ± 9.1 Spicara flexusa 320 7.1 23.2 15.2 ± 3.1 4 120 36.4 ± 22.8 29.4 ± 11.6 S. maena 380 7.5 22.9 13.4 ± 2.2 5.2 105 S. smaris 350 5.8 17.3 12.1 ± 2.0 2.2 60 18.2 ± 9.1 Solea solea 478 11 39 21.8 ± 3.5 11.5 670 101.6 ± 54.4 60.3 ± 43.5 S. aegyptiaca 510 9.9 31 18.3 ± 3.3 9 345 Microchirus ocellatus 400 6 21 11.8 ± 1.8 4 70 22.7 ± 5.3 Pegusa impar 410 7 22 12.6 ± 2.1 6.9 100 40.1 ± 20.2 Pegusa lascaris 380 13.9 29 20.8 ± 3.4 20 265 99.3 ± 45.6 Bothus poda 538 5 22.9 12.8 ± 2.9 1.6 140 26.2 ± 9.1 Arnoglosus laterna 315 7 20.5 12.1 ± 2.1 2.5 60 14.4 ± 3.4 Sardina pilchrdus 600 6.2 26 15.8 ± 1.9 2.1 145 40.3 ± 3.6 Sardinella aurita 870 8.1 23 12.9 ± 2.5 3.8 85 18.5 ± 10.0 47.7 ± 10.3 Etreumus teres 630 9 25 16.8 ± 3.8 7.9 170 Herktotsichthys punctatus 900 5 11.7 7.9 ± 0.9 1 15 5.5 ± 1.3 Nemipterus randalli 385 9 27 15.6 ± 3.4 8.5 330 72.6 ± 55.2 Nemipterus zysron 372 13 34 23.6 ± 4.1 19.9 395 145.8 ± 72.8 Nemipterus japonicus 457 6 34 22.9 ± 5.9 4 500 183.1 ± 111.7 Merluccidae Merluccius merluccius 530 15.1 63 26.4 ± 5.3 25 2,000 127.0 ± 82.8 Sphyraenidae Sphyraena sphyraena 249 15 84 49.9 ± 9.5 17 1,940 642.5 ± 325.6 Mullus surmuletus 630 6 29.1 17.4 ± 5.1 1.8 300 80.5 ± 68.2 M. barbatus 600 5 24.5 14.4 ± 4.4 1.5 175 40.1 ± 33.7 Upeneus pori 628 8 19 12.9 ± 1.9 7 70 22.6 ± 5.1 U. moluccensis 601 9 21.2 14.5 ± 2.4 8 90 30.3 ± 5.3 Moronidae Dicentrarchus labrax 418 19 64 30.4 ± 7.8 60 2,850 344.1 ± 235.5 D. punctatus 513 13 35 23.3 ± 3.8 24 390 116.8 ± 60.1 Synodontidae Saurida undosquamis 361 9.5 31 18.3 ± 5.3 5.4 214 54.5 ± 51.7 Synodus saurus 330 13 33 23.2 ± 5.0 17.1 335 113.4 ± 90.4 Mullidae Siganidae Siganus rivulatus 430 10 26.3 17.9 ± 3.8 11 225 79.1 ± 33.7 Hemiramphidae Hemiramphus far 510 15 31 22.9 ± 2.3 24 160 73.5 ± 22.1 Mugilidae Mugil cephalus 480 19 60 34.9 ± 6.5 63 2,065 425.3 ± 243.9 Liza ramada 600 12 42 25.9 ± 5.1 20 725 152.4 ± 96.5 L. aurata 520 14 31 22.2 ± 2.5 21 265 88.1 ± 21.3 (Continued) Frontiers in Marine Science | www.frontiersin.org 3 July 2021 | Volume 8 | Article 625422 Mehanna and Farouk LWR of 60 Species From GFCM-GSA 26 TABLE 1 | Continued Family Scientific name No. Length range (cm) Min Max Weight range (g) Mean Min Max Mean L. saliens 400 13 21 16.4 ± 1.9 20 90 49.3 ± 13.2 Chelon labrosus 400 17 35 24.2 ± 3.9 50 455 149.9 ± 77.7 Citharidae Citharus linguatula 400 6 20.5 12.7 ± 3.1 1 70 23.8 ± 5.3 Balistidae Balistes capriscus 240 16 53 24.1 ± 5.6 180 1,700 320.7 ± 151.5 100.4 ± 25.6 Trichuridae Trichiurus lepturus 320 20 64 33.5 ± 7.8 15 600 Engraulididae Engraulis encrasicolus 1,000 4 13 7.8 ± 0.9 0.4 19 4.6 ± 0.45 Fistularidae Fistularia commersonii 380 12 81 37.9 ± 9.3 9 1,600 263 ± 111.2 Sciaenidae Argyrosomus regius 390 17 70 38.1 ± 12.1 55 3,000 990 ± 123.8 Umbrina cirrosa 330 12 35 19.5 ± 4.8 25 500 108.5 ± 52.6 coefficient of determination (r2 ) for 60 pelagic and demersal fish species from the Mediterranean Sea GSA 26 are given in Tables 1, 2. The sample size fluctuated between 98 individuals for Epinephelus aenus and 1,326 ones for Pagellus erytherinus. The total lengths (TL) ranged from 4 cm for Engraulis encrasicolus to a total length of 100 cm for E. aenus, while the weights were varied between 0.9 and 11,000 g. The largest and the heaviest species was E. aenus with a maximum TL of 100 cm and a weight of 11,000 g. Fishes belonging to the family Sparidae were the best-represented species in the collected samples with 11 species, followed by families Soleidae and Mugilidae, where both of them were represented by five species. Eleven species were found to be of Indian Ocean origin and migrated through Suez Canal and were established in the eastern Mediterranean (Etreumus teres, Herklotsichthys punctatus, Nemipterus randalli, N. zysron, N. japonicas, Upeneus pori, U. moluccensis, Saurida undosquamis, Siganus rivulatus, Hemiramphus far, and Fistularia commersonii). It is worth mentioning that these species provide economic benefits to fishers and the coastal communities as up to 50% of Egyptian Mediterranean production constitutes Lessepsian migrants (Mehanna, 2015; General Authority for Fish Resources Development, 2018). In this study, the estimated b values for all the species were found within the normal expected range of 2 and 4 for teleosts (Tesch, 1971) and mostly remained within the expected range of 2.5–3.5 (Zar, 1996; Froese, 2006). The relationship between length and weight differs among fish species according to the body shape, and within the same species according to the condition (robustness) of individual fish. LWRs are not constant over the year and LWR parameters may vary significantly due to food availability, biological, temporal, and sampling factors. All regressions were highly significant, with the coefficient of determination (r2 ) ranging from 0.80 to 0.99 (p < 0.01). The b values ranged from 2.405 for Serranus hepatis to 3.270 for Boops boops. According to the t-test and CI analysis, the growth type of the 60 species fluctuated between allometric and isometric growth. About 18 species had a positive allometric growth (b > 3), 20 species caught from both the bottom survey and the commercial catch in the Egyptian Mediterranean GSA 26 (Figures 1, 2). MATERIALS AND METHODS The length and weight measurements were recorded during the bottom trawl surveys in the Mediterranean Sea of Egypt during the period from April 2008 to July 2010 and were updated by collecting and measuring more samples from the commercial catches along with the landing sites during the period from July 2017 to December 2018. A total of 30,596 fish of 60 fish species were measured and weighed. The total length (cm) of each fish was measured from the tip of the snout (mouth closed) to the extended tip of the caudal fin using a measuring board. Bodyweight was recorded to the nearest gram using a balance. The LWRs were estimated from the allometric formula, W = a Lb (Le Cren, 1951), where W is total body weight (g), L is the total length (cm), a and b are the coefficients of the functional regression between W and L (Beckman, 1948; Ricker, 1973). The values of constants a and b were estimated by the least-square linear regression from the log-transformed values of length and weight: log W = log a + b log L (Zar, 1984; Stergiou and Politou, 1995; Sivashanthini et al., 2009). The regression was done using Excel software, and all calculations were done for both sexes combined, as in many cases, dissecting and determining the sex of specimens seems to be difficult. To confirm whether the values of b obtained in the linear regressions were significantly different from the isometric value (b = 3), the confidence interval (CI) at 95% was estimated (isometric if b equal or very close to 3 and allometric if b significantly different from 3; negative allometric if b < 3 and positive allometric if b > 3) (Bagenal and Tesch, 1978). In addition, Student’s t-test (Zar, 1984) was used to see if parameter b is significantly different from 3 and to identify the type of growth. RESULTS AND DISCUSSION The sample size, minimum and maximum lengths and weights, LWRs, 95% confidence limits of b values (± 95% CI of b), Frontiers in Marine Science | www.frontiersin.org 4 July 2021 | Volume 8 | Article 625422 Mehanna and Farouk LWR of 60 Species From GFCM-GSA 26 TABLE 2 | Length-weight relationship (LWR), the confidence interval (CI) for b-value, and growth type (GT) for 60 fish species caught from the GSA 26. Species Sparidae Carangidae Serranidae Triglidae Spicaridae Soleidae Bothidae Clupeidae Nemipteridae Merluccidae Sphyraenidae Mullidae Moronidae Synodontidae Siganidae Hemiramphidae Mugilidae Citharidae Balistidae Trichuridae Engraulididae Fistularidae Sciaenidae Sparus aurata Pagellus erythrinus P. acarne Boops boops Lithognathus mormyrus Diplodus annularis D. sargus D. vulgaris D. cervinus hottentotus Pagrus pagrus Dentex dentex Trachurus trachurus T. mediterraneus Epinephelus aenus Serranus hepatus Serranus cabrilla Chelidonichthys lucerna Trigloporus lastovisa Lepidotrigla dieuzeidei Spicara flexuosa S. maena S. smaris Solea solea S. aegyptiaca Microchirus ocellatus Pegusa impar Pegusa lascaris Bothus poda Arnoglosus laterna Sardina pilchrdus Sardinella aurita Etreumus teres Herktotsichthys punctatus Nemipterus randalli Nemipterus zysron Nemipterus japonicus Merluccius merluccius Sphyraena sphyraena Mullus surmuletus M. barbatus Upeneus pori U. moluccensis Dicentrarchus labrax D. punctatus Saurida undosquamis Synodus saurus Siganus rivulatus Hemiramphus far Mugil cephalus Liza ramada L. aurata L. saliens Chelon labrosus Citharus linguatula Balistes capriscus Trichiurus lepturus Engraulis encrasicolus Fistularia commersonii Argyrosomus regius Umbrina cirrosa L-W relationship constants a b r2 CI GT* 0.0109 0.0096 0.0069 0.0044 0.0169 0.0217 0.0175 0.0225 0.0118 0.0179 0.0108 0.0132 0.0227 0.0551 0.0552 0.0167 0.0048 0.0111 0.0091 0.0091 0.0130 0.0079 0.0066 0.0056 0.0460 0.0058 0.0050 0.0157 0.0051 0.0071 0.0149 0.0091 0.0090 0.0161 0.0086 0.0090 0.0046 0.0066 0.0104 0.0077 0.0090 0.0091 0.0078 0.0111 0.0060 0.0055 0.0112 0.0044 0.0098 0.0184 0.0085 0.0121 0.0136 0.0055 0.0166 0.0007 0.0043 0.0038 0.0114 0.0117 3.091 3.118 3.221 3.270 2.869 2.840 2.921 2.914 3.137 2.950 3.029 2.856 2.732 2.724 2.405 2.853 3.222 2.986 3.052 3.052 2.988 3.069 3.092 3.146 2.461 3.137 3.187 2.901 3.101 2.912 2.745 3.036 3.049 2.8331 3.0266 3.0817 3.1191 2.890 3.0617 3.1095 3.0817 3.0501 3.055 2.9448 3.0656 3.1171 2.9844 3.080 2.979 2.751 2.936 2.929 2.897 3.086 3.081 3.301 3.278 2.935 2.976 3.011 0.98 0.98 0.93 0.98 0.97 0.91 0.98 0.91 0.96 0.98 0.93 0.97 0.97 0.97 0.96 0.98 0.97 0.97 0.90 0.90 0.96 0.94 0.91 0.88 0.95 0.95 0.96 0.97 0.90 0.94 0.94 0.97 0.96 0.96 0.95 0.97 0.97 0.97 0.97 0.98 0.97 0.98 0.98 0.99 0.95 0.95 0.97 0.92 0.98 0.94 0.96 0.89 0.97 0.97 0.85 0.93 0.93 0.93 0.95 0.97 2.889–3.105 2.998–3.237 3.182–3.260 3.196–3.345 2.841–2.896 2.791–2.889 2.889–2.953 2.900–2.928 3.128–3.156 2.931–2.969 2.999–3.059 2.779–2.934 2.698–2.766 2.671–2.776 2.178–2.632 2.743–2.962 3.185–3.260 2.948–3.024 2.992–3.112 2.945–3.034 2.953–3.023 2.964–3.174 3.060–3.125 3.104–3.189 2.421–2.501 3.077–3.197 3.134–3.240 3.021–3.161 3.051–3.151 2.887–2.937 2.724–2.767 3.012–3.059 2.909–3.189 2.773–2.892 2.877–3.169 2.982–3.181 3.069–3.169 2.809–2.971 2.998–3.125 3.062–3.157 2.982–3.181 2.988–3.112 2.971–3.139 2.978–2.911 2.983–3.148 2.890–3.344 2.915–3.054 3.022–3.138 2.918–3.039 2.727–2.780 2.889–2.991 2.901 ± 2.957 2.842–2.952 3.025–3.145 3.031–3.131 3.241–3.361 3.187–3.369 2.785–3.085 2.886–3.066 2.958–3.064 I I PA PA NA NA NA NA PA NA I NA NA NA NA NA PA I I I I I PA PA NA PA PA PA PA NA NA PA I NA I I PA NA I PA I I I NA I I I PA I NA NA NA NA PA PA PA PA I I I *I, isometric growth; PA, positive allometric; NA, negative allometric. Frontiers in Marine Science | www.frontiersin.org 5 July 2021 | Volume 8 | Article 625422 Mehanna and Farouk LWR of 60 Species From GFCM-GSA 26 species had negative allometric growth (b < 3), and 22 species showed isometric growth (Table 2). Most of the LWR obtained from this study agreed with those reported from the previous ones. The estimated growth type in this study coincides with those previously recorded (Moutopoulos and Stergiou, 2002; Mehanna, 2007a,b, 2019b; Adam, 2010; Abdel-Hakim et al., 2010; Demirel and Murat Dalkara, 2012; Torres et al., 2012; Bilge et al., 2014; Kara et al., 2017; Huang et al., 2018). In comparison with the earlier estimates, some variations in b values in the present study were observed, which may be attributed to various factors, such as fish physiology, growth phase, sex, sexual maturity, season, stomach fullness, length range and sampling size, habitat, feeding rate, diet, and health (Le Cren, 1951; Froese et al., 2011; Mondol et al., 2017). Based on the published literature and FishBase database (Froese and Pauly, 2021), no information on LWRs of 35 species is available from GSA 26. Therefore, this study provides new LWRs estimates for 35 species from the Egyptian Mediterranean waters. important demersal and pelagic fish species in GFCM-GSA 26. The results obtained from this study are useful to fisheries biologists as it updated length-weight parameters for some species and estimated these parameters for the first time for many species inhabiting the eastern Mediterranean Sea GSA 26. Even though these parameters were estimated for sexes combined, they still have great importance for fisheries managers as there are no specific gears for each sex and any fisheries regulations are taken for the whole stock or population. CONCLUSION SFM suggested the point of research, joined the surveys and the collection of samples, analyzed the data and wrote the manuscript. AEF shared in the surveys and sampling trips, and shared in taking the biological measurements in the lab. Both authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication. DATA AVAILABILITY STATEMENT The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s. AUTHOR CONTRIBUTIONS The basic biological information, such as LWRs, generated from this investigation will be useful for further population studies and stock assessment which in turn find its application in sustainable management measures of these commercially REFERENCES Froese, R., and Pauly, D. (eds). (2021). FishBase. World Wide Web Electronic Publication. Available online at: www.fishbase.org (accessed June, 2021). Froese, R., Tsikliras, A. C., and Stergiou, K. I. (2011). Editorial Note on Weight– Length Relations of Fishes. Acta Ichthyol. 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Frontiers in Marine Science | www.frontiersin.org Conflict of Interest: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Publisher’s Note: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher. Copyright © 2021 Mehanna and Farouk. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). 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