Boat Noise and Black Drum Communication in Mar Chiquita Coastal Lagoon (Argentina)

Abstract

The Mar Chiquita coastal lagoon (Buenos Aires, Argentina) has an important conservation value for its unique ecosystem. It is classified as a Man and the Biosphere Reserve (MAB, UNESCO, Iribarne 2001) and it is an important area of tourism and local fishing. From September 1st to December 1st, during the week days, a partial ban of fishing activities is imposed in order to protect the reproductive period of silversides Odontesthes spp.. However, the black drum, Pogonias cromis, is also an important fish species presents in the lagoon (Cousseau and Perrotta, 2004). During the reproductive period, males produce drumming sounds as advertisement calls characterized by frequency at approximately 150 Hz (Locascio et al 2011). Boat noise may overlap P. cromis sounds causing a potential masking effect (Smott et al. 2018), but it is not known if communication is altered. Aims of our study are to: 1) evaluate the effects of different boat noises on P.cromis acoustic communication 2) analyse the effectiveness of fishing ban activity from an acoustic point of view.Acoustic data were collected during November 2017 by using an autonomous recorder equipped with a Benthowave BII 7016 T6 hydrophone. The sample frequency was 192 kHz at 16 bit, alternating 2 minutes of recordings and 8 minutes of pause.All the dataset was visually inspected. P. cromis sounds were identified and counted combining pulse train analysis of Avisoft SASlab pro. The number of files where boat noise passages were recorded was counted. To quantify the potential impact of the boat noise, they were categorized relating to their frequency extension: 1) Class A, when the noise extension was below 700 Hz; 2) Class B, when the noise extension was only over 700 Hz; 3) Class C, when the noise extension covered below and over 700 Hz. We recorded boat noise during fish signal emission on 12,8 % of data. We found that the presence of boat noise significantly affected the number of fish signals (Welch´s Test p<0.001); boat noise that overlap the fish signals frequency (Class A and C) significantly reduced the number of fish signals (Tamhane post-hoc, p<0.001). The ban of Odontesthes spp. fishing determined the reduction of boat noise class C (U-Mann Whitney test: Z=-3,025, p>0.01) but it doesn´t affect the other kind of noises. The results show the degree of noise impact on P. cromis communication and underline the importance to adapt the current management of human impacts.