AEI 10:291-307 (2018) - DOI: https://doi.org/10.3354/aei00268
Hydrodynamics of a channel occupied by the aquaculture industry in southern Chile: implications for connectivity between farms
Marcus Sobarzo1,2,*, Luis Bravo3,4, Claudio Iturra5, Alfredo Troncoso1, Roberto Riquelme6, Patricio Campos7, Cristian Agurto8
ABSTRACT: Residual circulation from nonlinear interaction of the tidal currents with topography in channels, fjords and bays can be important to represent the distance traveled by suspended materials in the water column (e.g. pathogens). Here the role of the semidiurnal tidal excursion was compared with residual currents, during autumn 2011, to evaluate the connectivity among aquaculture production centers in Caucahue Channel (Chiloe Island, southern Chile), which has been widely occupied by the aquaculture industry. During 2015, around 30000 t of 3 different species of salmon were harvested in this channel, representing 3.7% of the national production. Along- and cross-channel tidal currents explained around 80 and 40-60% of the total variance, respectively. Thus, the major residual circulation came from the cross-channel component (40-60% of the total variance) caused by tidal asymmetry. We hypothesized that this asymmetry is related to the nonlinear interaction of the oscillatory flow with the Quemchi constriction. The residual advective distances (Ladv) were compared with tidal excursion (Lexc) and biological diffusivity (Ldiff) scales, considering the distances between centers (Lint), the size of the centers (Lcen) and the length of the south arm of the Cauchaue Channel (L = 11 km). For 3 d time scales, the Ladv/Lexc ratio fluctuated between 1.3 and 8, approximately, implying that, although the advective scale is greater, the tidal flow is still intense enough to favor the retention of pathogens. For larger time scales that consider longer-lived pathogens (e.g. greater than 15 d), this ratio grows 1 order of magnitude. In this scenario and in the event of an outbreak within the channel, pathogens could be exported.
KEY WORDS: Tidal excursion · Long-term residual advection · Tidal asymmetry · Chilean aquaculture industry · Waterborne pathogens
Full text in pdf format  | Cite this article as: Sobarzo M, Bravo L, Iturra C, Troncoso A, Riquelme R, Campos P, Agurto C
(2018) Hydrodynamics of a channel occupied by the aquaculture industry in southern Chile: implications for connectivity between farms. Aquacult Environ Interact 10:291-307. https://doi.org/10.3354/aei00268
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