Mean temperature of the catch (MTC) in the Greek Seas based on landings and survey data

Athanassios C Tsikliras,George Tserpes,Konstantinos I Stergiou,Panagiota Peristeraki

doi:10.3389/fmars.2015.00023

Athanassios C Tsikliras, George Tserpes + Show 2 more

Open Access

https://doi.org/10.3389/fmars.2015.00023

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Abstract

The mean temperature of the catch (MTC), which is the average inferred temperature preference of the exploited species weighted by their annual catch, is an index that has been used for evaluating the effect of sea warming on marine ecosystems. In the present work, we examined the effect of sea surface temperature on the catch composition of the Greek Seas using the MTC applied on the official catch statistics (landings) for the period 1970-2010 (Aegean and Ionian Seas) and on experimental bottom trawl survey data for 1997-2014 (southern Aegean Sea). The MTC of the landings for the study period increased from 11.8 οC to 16.2 οC in the Aegean Sea and from 10.0 οC to 14.7 οC in the Ionian Sea. Overall, the rate of MTC increase was 1.01 οC per decade for the Aegean and 1.17 οC per decade for the Ionian Sea and was positively related to sea surface temperature anomalies in both areas. For the survey data, the increase of the MTC of the bottom trawl catch in the southern Aegean Sea was lower (0.51 οC per decade) but referred to a shorter time frame and included only demersal species. The change in MTC of official and survey catches indicates that the relative catch proportions of species preferring warmer waters and those preferring colder waters have changed in favour of the former and that this change is linked to sea surface temperature increase, both internally (through the Atlantic Multidecadal Oscillation) or externally (warming trend) driven.

Highlights

The effect of sea temperature increase (Levitus et al, 2000; for the Mediterranean Sea see Bethoux and Gentili, 1999) on the distribution and abundance of marine fish populations is well established for the Mediterranean Sea (e.g., Sabates et al, 2006; Tsikliras, 2008; Tzanatos et al, 2014)
Based on the officially recorded catch statistics, mean temperature of the catch (MTC) increased from 11.8◦C in 1970 to 16.2◦C in 2010 in the Aegean Sea and from 10.0◦C in 1970 to 14.7◦C in 2010 in the Ionian Sea (Figure 1)
The increase of MTC in both Ionian and Aegean Seas was positively related to sea surface temperature (SST) anomalies (Figure 1; columns)

Summary

Introduction

The effect of sea temperature increase (Levitus et al, 2000; for the Mediterranean Sea see Bethoux and Gentili, 1999) on the distribution and abundance of marine fish populations is well established for the Mediterranean Sea (e.g., Sabates et al, 2006; Tsikliras, 2008; Tzanatos et al, 2014). Over 435 species have invaded the Mediterranean Sea through the Suez Canal, about 50% of which are molluscs and arthropods and 20% are fishes (Nunes et al, 2014). These invaders, some of which have established viable populations, certainly change the faunal composition but may cause severe alterations to ecosystem structure and function (Sala et al, 2011; Bianchi et al, 2014). In certain areas of the eastern Mediterranean some alien fishes are commercially exploited (Kallianiotis and Lekkas, 2005; Giakoumi, 2014) but their catches are not yet officially recorded (Tsikliras and Stergiou, 2014b), at least not as separate records

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