Internal tidal waves in Tiburon Basin (Gulf of California, Mexico) modulate fish larvae aggregations

To analyze the effects of internal tidal waves on fish larvae, a cruise was conducted (September 2012) in Tiburon Basin (∼400 m depth) in the Midriff Archipelago of the Gulf of California, an area of strong internal wave activity during periods of stratification. The temperature and current fields were correlated with the semidiurnal tide. The internal tide reached heights of ∼15 m, although a high-frequency event (period < 1 h) displaced isotherms up to 25 m. The kinetic energy was relatively high (>60 J m ⁻³ ) for most of the sampling period. An increase in species richness and in the abundance of fish larvae was related to periods of high kinetic energy. A cluster analysis showed the presence of two groups of fish larvae. One group was associated with periods of high kinetic energy (>60 J m ⁻³ ), with high fish larvae abundance (435 org 1000 m ⁻³ ) and the frequent occurrence of coastal-demersal species (i.e. Erotelis armiger and Lythripnus zebra). A second group was associated with low kinetic energy (<35 J m ⁻³ ) and had low fish larvae abundance (22 org 1000 m ⁻³ ) and the absence of many coastal-demersal species. Results suggest that periods of high kinetic energy associated with internal tidal waves may be favorable for larval fish accumulation and may modulate fish larval assemblages in the Midriff Archipelago Region.