Contrasting multispecies patterns in larval fish production trace inter-annual variability in oceanographic conditions over the N.E. Aegean Sea continental shelf (Eastern Mediterranean)

Abstract

The response of larval fish communities of the northeastern Aegean Sea (NEA) to interannual environmental changes is analyzed using data from four ichthyoplankton surveys covering the NEA continental shelf during June 1993June , 1994June , 1995June , and 1996. Waters were significantly cooler, less saline and richer in zooplankton in 1993 and 1996 ('cold' years) than in 1994 and 1995 ('warm' years). A comparison of monthly SST series (1993)(1994)(1995)(1996)(1997) between the NEA, the Marmara Sea, and the Western Black Sea revealed high correlations and similar trend components among these areas implying that oceanographic conditions over the NEA (and observed inter-annual differences) were most likely dominated by the properties and relative amount of Black Sea water inflow in the NEA. The relative composition of the larval fish community was significantly related to the 'cold/warm' regime and larval diversity was higher during the warm years. Larvae of the small-sized pelagic species, such as anchovy (Engraulis encrasicolus), and most mesopelagic fishes were relatively more abundant during the cold, zooplankton-rich years. Larvae of the middlesized pelagics (Sardinella aurita, Scomber japonicus, Trachurus mediterraneaus, Auxis rochei) and certain benthopelagic species exhibited an opposite trend, i.e., they were more abundant during the warm years or absent during the cold years. Most of these species are known to be typical summer spawners (e.g., Serranus cabrilla, Lisa saliens, Trachinus draco, and Symphurus nigrescens). Co-variation in larval fish production might be indicative of similar responses among species to changing physical and/or trophic regimes.

Spatial and temporal patterns of fish larvae assemblage in the Northern coastal waters of Persian Gulf along the Bushehr province shoreline

“…These results are consistent with other ichthyoplankton studies on continental shelves around the world (Somarakis et al, 2002, Kendall & Dunn. 1985, Espinosa-Fuentes & Flores-Coto.2003, Somarakis et al, 2011. However the effect of depth was reduced in cold seasons, since other factors such as marine currents which intensifies due to prevailing local winds, will affect the transportation of fish larvae specially Gobiids to offshore areas, and consequently representing more abundance in this region.…”

Using spatial indicators to investigate fish spawning strategies from ichthyoplankton surveys: A case study on co-occurring pelagic species in the NE Aegean Sea

“…According to Cengiz (2012), chub mackerel spawn between June and August in the NEA. This delay in the onset of the spawning period of chub mackerel when compared to anchovy and round sardinella could be attributed to the chub mackerel's higher temperature threshold for the initiation of the annual spawning period (Somarakis et al, 2011a). Finally, in July 2010, the abundance of anchovy eggs was markedly higher when compared to the other two pelagic species.…”

“…As an adaptation to the seasonality of the marine environment in temperate and sub-tropical ecosystems, fish have evolved to take advantage of optimal environmental conditions for egg maturation and spawning (Winemiller & Rose, 1992;Lowerre-Barbieri et al, 2011). Similar temporal patterns on the occurrence and relative abundance of different egg and larval species in plankton may indicate similar reproductive strategies (Somarakis et al, 2000;Somarakis et al, 2011a).…”

“…Chub mackerel and round sardinella also spawn during the summer months, with peak spawning in June-July (chub mackerel in the Adriatic Sea (Cikeš Keč & Zorica, 2012); round sardinella in the Adriatic Sea (Mustać & Sinovčić, 2012); and Aegean Sea (Tsikliras, 2006)). Comparative studies of the egg and larval distributions of these species in the northwest (Sabatés et al, 2009(Sabatés et al, , 2013 and eastern Mediterranean (Somarakis et al, 2002;Isari et al, 2008;Schismenou et al, 2008;Tsikliras et al, 2009;Somarakis et al, 2011a) have mainly focused on inter-annual differences, usually during peak spawning period. However, there are few studies that describe the spawning activity of anchovy and other summer-spawning pelagic species that have covered more extended periods of the spawning season in the Aegean Sea (e.g.…”

Spatial distribution of tuna larvae in the Gulf of Gabes (Eastern Mediterranean) in relation with environmental parameters

“…Atlantic bluefin tuna larvae appeared within SST varying from 24.28 to 24.69° C, whereas bullet tuna and Atlantic black skipjack were found in waters between 24.1 and 25.44°C, coinciding with those reported by previous studies. For instance, Garcia et al (2005 a, b) reported that in the Balearic Sea, Atlantic bluefin tuna spawning takes place preferentially in the mixing zones between Atlantic and Mediterranean waters, from late June to July, in sea surface temperatures ranging between 23.5 and 25° C. Moreover, in the Catalan Sea, Sabatés & Recasens (2001) captured a high number of bullet tuna larvae when the sea surface temperature ranged between 23.7 and 25.4° C. In the northeast Aegean Sea, Somarakis et al (2011b) concluded that bullet tuna larvae were more abundant during the warm season. Dicenta & Piccinetti (1978) reported that in the western Mediterranean, T. thynnus and A. rochei larvae were found when SST ranged from 20.88 to 26.32° C and between 19.11 and 26.32° C respectively.…”