Acoustic Conditioning System Development an

1 Introduction

Sea ranching is defined as ‘the release of young, hatchery-reared fish into inshore waters for subsequent on-growing and recapture by private, public, or co-operative beneficiaries’ (Pickering, 1999). It can be compared with agricultural practices, where the coastal region is the field, the juveniles are the seeds, and the harvested fishes are the crops (Zion and Barki, 2012). Because of the absence of a fence to restrict the activity range of the fish in sea ranching, the most challenging hurdle is to attract the released fish to designated areas and to ensure that they remain there. This attraction is achieved through a series of methods and techniques. There are basic conditions that are required to enhance fish stocks, such as a comfortable habitat with enough bait, a favorable environment with an entire ecosystem, and suitable places to hide from predators (Burkepile and Hay, 2008). Sea ranches have the potential to meet all these requirements;however, the results from fish behavior tracking research have shown that sea ranches alone are not sufficient to attract the released juveniles to remain in the expected areas (Hwang and Jang, 2014; Pursche et al., 2014).Some fishes were found tens of kilometers away from the designated location only several days after being released,indicating the requirement of more systematic successfully guide a large proportion of the released juveniles, more advanced technologies or methods need to be adopted in sea ranch operations, such as 1) fish species selection based on weak migratory behavior, 2) the culture and release techniques of juveniles in net cages, 3)continuous fish behavior intervention in the open sea, and 4) sustainable management and recapture (Zion et al.,2014).

The use of artificial reefs is the most popular method to improve open sea habitats. Rock reef has been demonstrated to be attractive to fish in multiple ocean areas,such as the Gulf of Mexico; the coastal areas of Japan,Brazil, and Australia; the North Pacific, Indian, and North Atlantic oceans; the Mediterranean Sea; the Red Sea; and the South China Sea (Brottoet al., 2006; Burkepile and Hay, 2008; Han et al., 2008; Hunter and Sayer, 2009; Sala et al., 2008). Fabi and Sala (2002) pointed out that the fish density appeared to be the highest in the reef and that the density decreased sharply 80 m away from the on the above-mentioned results and observations,artificial reefs have been constructed on suitable sea beds to improve the fish habitat in East Asia (Noguchi, 1996;Lee, 2015). In China, 42 sea ranches have been constructed along the coastal regions. Fig.1 shows the artificial reef and kelp culture in the Xiangshan Bay sea investigations have shown that fish stocks and other biological resources have been dramatically improved in artificial reef areas (Hwang and Jang, 2014;Melendez et al., 2015).

Fig.1 Artificial reefs and kelp cultures in the Xiangshan Bay sea ranch.

Artificial reefs and seaweed cultures provide favorable environments for the fish; however, they are not sufficient to attract the fish to live in the sea ranch for a long is a natural factor that attracts fish to a reef(Bhandiwad et al., 2017). Simpson et al. (2005) introduced the attraction experiment to the Great Barrier Reef in Australia and found that the noisiness of the fish on the coral reef was attractive to related species. Tolimieri et al.(2000) arranged light and sound attracting instruments on reefs and conducted experiments over 14 days. They demonstrated that the attraction validity of sound is better than that of light. Leis et al. (2003) found that the fish quantity increased by 45% with sound attraction. Extensive researches have been conducted on the applications of acoustic conditioning associated with bait to control fish behavior. In a deep-sea net cage, Tlusty et al. (2008)adopted acoustic signals to control the escaped fish and called them back. Zhang et al. (2004) and Jiang et al.(2008) applied sound to tame the black seabream (Sparus macrocephalus) and the red seabream (Chrysophrys major) by simple sound frequency in the laboratory. The above-mentioned research indicates that sound can affect fish behavior. Teodosio et al. (2016) proposed that sound could be used as a cue to guide the fish larvae to estuarine nursery areas.

Fish behavior intervention using acoustic conditioning is an important technique for attracting fish to sea ranching areas. The black seabream is an economically valuable fish species in the east Asian coastal region (Cheng and Xu, 1989). The diet of black seabream includes small fish, shrimp, shell, seaweed etc. (Wu et al., 2015). Owing to its weak migratory behavior, the black seabream is one of the primarily bred and released fishes in the East China Sea. In light of previous research results and integrated with the environmental features of the East China Sea, the behavior control experiments were systematically conducted on black seabream in the Xiangshan Bay sea acoustic conditioning equipment was developed so that the operations could be left unattended. Experiments, including with both net cage training and open sea culture, as well as continuous and long-term operations, were successfully conducted. The results of our investigation demonstrated the validity of the acoustic conditioning system.

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