A study on European anchovy (Engraulis encrasicolus) swimbladder with some considerations on conventionally used target strength

Hydroacoustic surveys are one of the prime methods to assess the commercially top-ranked small pelagic stocks. The methodrelies on acoustic scattering from a fish, which is largely controlled by the size and morphology of the swimbladder. In this study, thechanges in the size of the European anchovy swimbladder sampled in the Black Sea were investigated. Ventral cross-sectional area (byphotographing the ventrally dissected fish) and volume (by dorsal and lateral X-raying) of the swimbladders were estimated. Comparisonof areas showed that the stomach fill and presence of viscera did not have a statistically significant impact on the swimbladder size whilethe hepatosomatic index showed significant impact. Although the vertical distribution of the anchovy is naturally not very wide due toabsence of sufficient oxygen below 100 m, sampling depth showed significant impact on the volume of the swimbladder. However, it wasalso observed during X-ray imaging that a considerable number of fish (87%) had deflated swimbladders. The reasons for this variability,which may have significant implication on the acoustic estimations and stock assessment, were also discussed. The importance ofacclimatization of the fish at surface conditions in studies addressing changes in swimbladder morphometry was underlined.

PDF

___

Alexander RM (1993). Buoyancy. In: Evans DH, editor. The Physiology of Fishes. Boca Raton, FL, USA: CRC Press, pp. 75-97.
Blaxter JHS, Denton EJ, Gray JAB (1979). The herring swimbladder as a gas reservoir for the acousticolateralis system. J Mar Biol Assoc 59: 1-10.
Blaxter JHS, Hunter JR (1982). The biology of the clupeoid fishes. Adv Mar Biol 20: 1-223.
Fassler SMM, Fernandes PG, Semple SIK, Brierley AS (2009). Depth-dependent swimbladder compression in herring Clupea harengus observed using magnetic resonance imaging. J Fish Biol 74: 296-303.
Fassler SMM, O’Donnell C, Jech JM (2013). Boarfish (Capros aper) target strength modelled from magnetic resonance imaging (MRI) scans of its swimbladder. ICES J Mar Sci 70: 1451-1459.
Fine ML, McKnight JW Jr, Blem CR (1995). Effect of size and sex on buoyancy in the oyster toadfish. Mar Biol 123: 401-409.
Foote KG (1980). Effect of fish behaviour on echo energy: the need for measurements of orientation distribution. ICES J Mar Sci 39: 193-201.
Foote KG (1985). Rather-high-frequency sound scattering by swimbladdered fish. J Acoust Soc Am 78: 688-700.
Ganias K, Michou S, Nunes C (2015). Field based study of swimbladder adjustment in a physostomous teleost fish. PeerJ 3: e892.
Graham MH (2003). Confronting multicollinearity in ecological multiple regression. Ecology 84: 2809-2815.
Gücü AC, Genç Y, Dağtekin M, Sakınan S, Ak O, Ok M, Aydın İ (2017). On Black Sea anchovy and its fishery. Rev Fish Sci Aquac 25: 230-244.
Hazen EL, Horne JK (2003). A method for evaluating the effects of biological factors on fish target strength. ICES J Mar Sci 60: 555-562.
Hodges RP (2010). Active target strength. In: Hodges RP, editor. Underwater Acoustics: Analysis, Design and Performance of Sonar. 1st ed. Chichester, UK: John Wiley and Sons, pp. 167- 183.
ICES (1983). Report of the Planning Group on ICES Coordinated Herring and Sprat Acoustic Surveys. ICES Document CM 1983/H:12. Copenhagen, Denmark: ICES.
Jones HFR, Marshall NB (2008). The structure and function of the teleostean swimbladder. Biol Rev 28: 16-82.
Machias A, Tsimenidis N (1995). Biological factors affecting the swimbladder volume of sardine (Sardina pilchardus). Mar Biol 123: 859-867.
Machias A, Tsimenides N (1996). Anatomical and physiological factors affecting the swimbladder cross-section of sardine Sardina pilchardus. Can J Fish Aquat Sci 53: 280-287.
MacLennan DN (1990). Acoustical measurement of fish abundance. J Acoust Soc Am 87: 1-15.
Ona E (1990). Physiological factors causing natural variations in acoustic target strength of fish. J Mar Biol Assoc 70: 107-127.
Pena H, Foote KG (2008). Modelling the target strength of Trachurus symmetricus murphyi based on high-resolution swimbladder morphometry using an MRI scanner. ICES J Mar Sci 65: 1751- 1761.
Pyrounaki ΜM, Machias Α, Giannoulaki Μ (2012). Target strength equations for anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) from acoustic surveys in Aegean Sea. In: Proceedings of the 10th Panhellenic Symposium of Oceanography and Fisheries; 10–11 May 2012; Athens, Greece. pp. 168-174.
R Core Team (2016). R: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing.
Robertson GN, Lindsey BW, Dumbarton TC, Croll RP, Smith FM (2008). The contribution of the swimbladder to buoyancy in the adult Zebrafish (Danio rerio): a morphometric analysis. J Morphol 269: 666-673.
RStudio Team (2017). RStudio: Integrated Development for R. Boston, MA, USA: RStudio, Inc.
Sawada K, Ye Z, Kieser R, Furusawa M (1999). Target strength measurements and modeling of walleye pollock and Pacific hake. Fisheries Sci 65: 193-205.
Scoulding B, Chu D, Ona E, Fernandes PG (2015). Target strengths of two abundant mesopelagic fish species. J Acoust Soc Am 137: 989-1000.
Silva A, Santos M, Caneco B, Pestana G, Porteiro C, Carrera P, Stratoudakis Y (2006). Temporal and geographic variability of sardine maturity at length in the northeastern Atlantic and the western Mediterranean. ICES J Mar Sci 63: 663-676.
Simmonds EJ, MacLennan DN (2005). Fisheries Acoustics: Theory and Practice. 2nd ed. Oxford, UK: Wiley-Blackwell.
Yasuma H, Sawada K, Ohshima T, Miyashita K, Aoki I (2003). Target strength of mesopelagic lanternfishes (family Myctophidae) based on swimbladder morphology. ICES J Mar Sci 60: 584- 591.
Zhao X, Wang Y, Dai F 2008. Depth-dependent target strength of anchovy (Engraulis japonicus) measured in situ. ICES J Mar Sci 65: 882-888.