Spring and summer ichthyoplankton assemblages in a temperate Patagonian gulf: an overview of temporal and spatial patterns on their structure

Abstract

Knowing about the spatio-temporal patterns in the structure of ichthyoplankton assemblages allows inferring about the spawning behaviour of adult fi shes, understanding the recruitment dynamics, and predicting the potential effects of mid-and long-term changes. Here, we studied the ichthyoplankton assemblages from the San José Gulf (Northern Patagonia, Argentina) and investigated their changes in space and time. To do that, we took monthly samples during two consecutive years, in spring and summer. A total of 2088 larvae were caught; they comprised 36 taxa, from which 14 were identifi ed to species, two to genus, one to family and one to order. There were large differences in the structure of the assemblages between years, coincidently with marked changes in the surface water temperature. The structure of the ichthyoplankton assemblages also showed signifi cant differences between the spring and summer: Helcogrammoides cunninghami, Dules auriga and larvae belonging to the family Engraulidae contributed most to these differences. The species diversity was higher in the colder year than in the warmer one. We discuss the potential role of environmental and oceanographic features on the interannual variability in the early stages of coastal fi shes within a small gulf.

Development and Occurrence of Early Stages of Dules auriga in the Northern Patagonian Gulfs of Argentina

“…However, its frequency of occurrence has increased and its distributional range expanded to the Southern Patagonian region (Galván et al, 2009, 2022). We found that its early stages are relatively common in samples from the SJG during the austral summer (Villanueva Gomila et al, 2020). Also, juveniles of D. auriga were caught in large numbers at depths rounding 50–60 m in the SJG, during the research cruise CONCACEN 2009 (Venerus, unpubl.…”

“…During the austral summer, SJG is subject to strong water exchanges with the San Matías Gulf (with evacuation times of 20 days on average; Tonini et al, 2022), where a high density of adults has been registered (Jerez et al, 2018). This could suggest that some early stages of D. auriga , which breeds from December to March and has a peak in February (Villanueva Gomila et al, 2020), come from the San Matías Gulf. As rocky reefs occur as patches in a flat environment that is otherwise hostile to shelter-seeking fishes, and the adults cannot migrate between remote patches (Walford, 1938; Norcross and Shaw, 1984; Smith et al, 1987), the planktonic life stages provide an advantage to organisms living on reefs by representing the most important dispersal mechanism.…”