UNIVERSITY OF THE AEGEAN SCHOOL OF ENVIRONMENTAL STUDIES DEPARTMENT OF MARINE SCIENCES Use of pitfall traps for sampling marine benthic arthropods on soft substrate BSc Thesis Dadaliaris Michail & Gkrantounis Pavlos Mytilene 2017 Ευχαριστίες Αρχικά κα κζλαμε να ευχαριςτιςουμε τον επιβλζποντα κακθγθτι τθσ διπλωματικισ μασ εργαςίασ κ. Στυλιανό Κατςανεβάκθ, πρωταρχικά ωσ επιςτιμονα και παιδαγωγό, για τθν ςυμβολι του ςτθν πανεπιςτθμιακι μασ εκπαίδευςθ και για τθν πολφτιμθ βοικεια του ςε όλθ τθ διάρκεια διεξαγωγισ τθσ πτυχιακισ διατριβισ και ακολοφκωσ ωσ άνκρωπο, διότι δεν δίςταςε να μασ παράςχει τθ βοικεια και τθ ςτιριξθ του ςε οποιαδιποτε δυςκολία ςυναντιςαμε ςτθ φοιτθτικι μασ ηωι. Τον κ. Ακανάςιο Ευαγγελόπουλο, για τθν αμζριςτθ βοικεια που μασ παρείχε, όλο αυτό το χρονικό διάςτθμα, ςτο εργαςτθριακό και ςυγγραφικό κομμάτι τθσ πτυχιακισ. Tθν κ. Μαρία Ναλετάκθ και τθν κ. Μαρία Μαϊδανοφ του ΕΛ.ΚΕ.ΘΕ για τθν ςυμβολι τουσ ςτθν αναγνϊριςθ των ειδϊν. Τθν φοιτθτικι καταδυτικι ομάδα ‘Τρίτων’ του Πανεπιςτθμίου Αιγαίου για τθν παραχϊρθςθ του καταδυτικοφ εξοπλιςμοφ, όπου δίχωσ αυτόν θ ζρευνα μασ κα ιταν αδφνατο να πραγματοποιθκεί. Τζλοσ κα κζλαμε να ευχαριςτιςουμε τισ οικογζνειζσ μασ και τουσ φίλουσ μασ, όπου χάρθ ςτθ ςτιριξθ τουσ, καταφζραμε να ανταπεξζλκουμε όλεσ τισ δυςκολίεσ αυτϊν των καιρϊν και να αναδειχκοφμε πτυχιοφχοι. Abstract Ecological monitoring is a prerequisite for ecosystem-based management and conservation. There is a need for developing an efficient and non-destructive method for monitoring marine benthic arthropods on soft substrate, as the currently applied methods are often inadequate. Pitfall trapping has been used extensively to sample terrestrial arthropods but has not yet seriously considered in the marine environment. In this study, the effectiveness of pitfall traps as a way to monitor marine benthic arthropods is assessed. It was found that pitfall traps can function successfully. In a pilot case study in Kalloni gulf (Lesvos island, Greece), two different trap types were tested at five depths during two 12-h periods (day and night). The hermit crab Diogenes pugilator (Roux 1829) dominated catches. The catch of this species significantly differed by trap type, while the interaction between depth and period was also found significant. Further research is needed to evaluate the efficiency of different types of traps and field protocols. Περίληψη Η οικολογικι παρακολοφκθςθ αποτελεί προχπόκεςθ για τθν διαχείριςθ και διατιρθςθ των οικοςυςτθμάτων. Είναι αναγκαία θ ανάπτυξθ μιασ αποτελεςματικισ και μθ-καταςτρεπτικισ μεκόδου παρακολοφκθςθσ καλάςςιων βενκικϊν αρκροπόδων ςε μαλακό υπόςτρωμα, κακϊσ οι μζκοδοι που ιδθ εφαρμόηονται είναι ανεπαρκείσ. Η παγίδευςθ αυτοφ του τφπου ζχει χρθςιμοποιθκεί εκτεταμζνα για δειγματολθψία χερςαίων αρκροπόδων, αλλά δεν ζχει ακόμθ εξεταςτεί ςοβαρά ςτο καλάςςιο περιβάλλον. Σε αυτι τθ μελζτθ,αξιολογείται θ αποτελεςματικότθτα των παγίδων ωσ μζςο παρακολοφκθςθσ καλάςςιων βενκικϊν αρκροπόδων. Διαπιςτϊκθκε ότι οι παγίδεσ μποροφν να λειτουργιςουν με επιτυχία. Σε μια πιλοτικι μελζτθ ςτον κόλπο τθσ Καλλονισ (Λζςβοσ, Ελλάδα), δοκιμάςτθκαν δφο διαφορετικοί τφποι παγίδων, ςε πζντε βάκθ, ςε δφο περιόδουσ 12 ωρϊν (θμζρα και νφχτα). Ο πάγουροσ Diogenes pugilator(Roux 1829) κυριάρχθςε ςτισ ςυλλιψεισ. Οι ςυλλιψεισ αυτοφ του είδουσ διζφεραν ςθμαντικά ανάλογα με τον τφπο παγίδασ, ενϊ θ αλλθλεπίδραςθ μεταξφ βάκουσ και περιόδου βρζκθκε ότι ιταν εξίςου ςθμαντικι. Χρειάηεται περεταίρω ζρευνα ϊςτε να εκτιμθκεί θ αποτελεςματικότθτα διαφορετικϊν τφπων παγίδων και πρωτοκόλλων πεδίου. Contents Introduction ............................................................................................................................... 1 Materials and Methods ............................................................................................................. 3 Case study area ..................................................................................................................... 3 Fieldwork ............................................................................................................................... 3 Laboratory analysis ................................................................................................................ 4 Data analysis .......................................................................................................................... 5 Results ....................................................................................................................................... 6 Discussion .................................................................................................................................. 8 References ............................................................................................................................... 10 Supplementary material .......................................................................................................... 14 Introduction Ecological monitoring can be defined as the process of collecting ecological data in a standardized way at regular time intervals, aiming to assess the state of the study system and its change over time (Yoccoz et al. 2001). Monitoring programs are essential to test competing ecological hypotheses about the functioning of ecosystems and their components, conduct impact assessments, operate early warning systems, assess the population status of protected and vulnerable species, manage biological resources, and to test the effectiveness of management actions (Katsanevakis et al. 2012). Monitoring is an essential component of adaptive management, noted as managing according to a plan by which decisions can be modified based on new knowledge about the system and assessments about the effects of previous management actions (Parma et al. 1998, Katsanevakis et al. 2011). There are several methods of ecological monitoring in the marine environment, such as plot sampling, distance sampling, mark-recapture methods, repeated presence-absence surveys for occupancy estimation, and removal methods, each suitable for different biodiversity components (Katsanevakis et al. 2012). Sampling methods are divided into destructive (e.g. trawls, dredges, grabs, corers) and non-destructive (e.g. based on visual observations, mark- recapture), the latter being the preferable or only alternative when monitoring protected species or conducting surveys in protected areas or vulnerable habitats. Although many of them can be used for monitoring benthic arthropods in shallow waters, there are considerable limitations of the existing methods. Dredges could be used but they are not applicable at shallow bottoms, and as any destructive method, should be avoided in marine protected areas or vulnerable habitats such as seagrass beds. Corers and grabs are ideal for endobenthic macrofauna, but due to the small sampled surface they are not suitable for larger and motile epibenthic species. Underwater visual surveys applying plot sampling or distance sampling techniques (Buckland et al. 2001) could be used but their basic assumptions cannot be always secured due to the often low detectability of benthic arthropods, which often hide or remain buried in the sediments. Mark-recapture methods using tags and dyes are applicable (Bakus 2007) but require high field effort to achieve good results. Therefore, for monitoring benthic arthropods there is a need to develop and test new sampling techniques. 1 In the terrestrial environment the most common technique used for sampling arthropods is pit fall trapping (Luff 1975, Buchholz 2010, Hancock 2012, Knapp 2012, Lang 2000, Schimmel 2010). Pitfall trapping is a sampling technique that has been used extensively for ecological studies and specifically for capturing invertebrates that are active on ground's surface. As the name suggests, the trap works on the principle that an arthropod moving on the ground simply falls into an open container dug into the ground. Pitfall traps are simple and easy to be installed, removed, transported or reinstalled. They have a low manufacturing cost since they usually consist of simple materials like plastic, glass or metal and they have circular, conical, rectangular or quadrangular shape. They can capture a big number and great diversity of species, so they can provide an impressive set of data (Gist &Crossley 1973). Species are caught undamaged and therefore it is easy to identify them. Also they can be set for long periods and they do not require any kind of power source. The existence of soft substrate is a prerequisite for the proper placement of traps. It is crucial for their performance that the mouth of the trap does not protrude from the bottom surface level. The time pitfall traps are left in the field depends on the nature of the sample survey; in long-term sampling, the containers should be checked regularly, in order to be empty and re-installed. The use of bait in the traps is a way for attracting more animals(Greensladed 1971, Ramsey et al. 1997).Also a killing-preserving agent can be used for direct killing and maintenance of the captured organisms in terrestrial areas(Skuhravy 1970). The method of pitfall trap capturing has been used for studies of community richness (Ward et al. 2001), habitat assessments (Samu & Sarospataki, 1995), monitoring and inventory of species(Rödel & Ernst 2004, Jonathan et al.2000), and the spatial pattern of distribution in populations (Thomas et al. 2001). To our knowledge, pitfall traps have not been used as yet for monitoring subtidal communities but only in very few