Frontiers in Marine Science (Nov 2015)
Patterns of recruitment of the sand smelt (Atherina presbyter) on rocky intertidal habitats
Abstract
The Portuguese coast is located in a biogeographical transition zone between temperate and subtropical waters making it especially vulnerable to the effects of climate change. Several fish species struggle to cope with these annual changing conditions, particularly species that strongly depend on intertidal habitats which are expected to endure higher ecological fluctuations. Sand smelt young recruits and larvae were collected at the west coast of Portugal in the intertidal by hand-netting, and in the subtidal with light traps and scuba diving with plankton nets attached to scooters (Parede/Avencas: 38º 41’ N, 9º 21’W and Arrábida: 38º 28’ N, 8º 59’W, respectively). Due to the morphological similarities with other congeneric species young specimens were regularly collected and identified through genetic analysis. All samples were assigned to the same species: A. presbyter. Results showed that A. presbyter is one of the most abundant non-resident fish species in these rocky coastal areas, representing 49% (n=93.958) of the total number of individuals sighted in the intertidal from 2009-2015, but only 0.55% of the total number of individuals sampled in the subtidal (n=176 with both methods) from 2011-2013. Distribution patterns showed that recruits (TL 0.8-6.8 cm) concentrated within the intertidal area between March and December. Younger cohorts (TL 0.8-1.2 cm) are captured almost exclusively in these areas including confined intertidal channels and large pools between March and August, suggesting that reproduction and spawning can occur for a period of 6 months. Inter-annual seasonal variations from 2009 to 2015 showed irregular water temperature profiles, especially in 2011 and 2012, which may dramatically affect the reproductive success of this species, not only reducing the number of recruits but also shortening the recruitment period from 10 to 5 months. Globally, 46% of the coastlines have experienced a significant decrease in the frequency of extremely cold events, becoming more common the occurrence of extremely hot events and fast temperature variations. As sand smelt is one of the most abundant cold/temperate fish species in temperate waters and a common prey item of many piscivorous species, a reduction of its reproductive success may unbalance food web relationships in temperate coastal communities and affect local fisheries economy.
Keywords
