Panagiotis Dendrinos

The Structure of Mediterranean Rocky Reef Ecosystems across Environmental and Human Gradients, and Conservation Implications

Historical exploitation of the Mediterranean Sea and the absence of rigorous baselines makes it difficult to evaluate the current health of the marine ecosystems and the efficacy of conservation actions at the ecosystem level. Here we establish the first current baseline and gradient of ecosystem structure of nearshore rocky reefs at the Mediterranean scale. We conducted underwater surveys in 14 marine protected areas and 18 open access sites across the Mediterranean, and across a 31-fold range of fish biomass (from 3.8 to 118 g m−2). Our data showed remarkable variation in the structure of rocky reef ecosystems. Multivariate analysis showed three alternative community states: (1) large fish biomass and reefs dominated by non-canopy algae, (2) lower fish biomass but abundant native algal canopies and suspension feeders, and (3) low fish biomass and extensive barrens, with areas covered by turf algae. Our results suggest that the healthiest shallow rocky reef ecosystems in the Mediterranean have both large fish and algal biomass. Protection level and primary production were the only variables significantly correlated to community biomass structure. Fish biomass was significantly larger in well-enforced no-take marine reserves, but there were no significant differences between multi-use marine protected areas (which allow some fishing) and open access areas at the regional scale. The gradients reported here represent a trajectory of degradation that can be used to assess the health of any similar habitat in the Mediterranean, and to evaluate the efficacy of marine protected areas.

Ecoregion-Based Conservation Planning in the Mediterranean: Dealing with Large-Scale Heterogeneity

Spatial priorities for the conservation of three key Mediterranean habitats, i.e. seagrass Posidonia oceanica meadows, coralligenous formations, and marine caves, were determined through a systematic planning approach. Available information on the distribution of these habitats across the entire Mediterranean Sea was compiled to produce basin-scale distribution maps. Conservation targets for each habitat type were set according to European Union guidelines. Surrogates were used to estimate the spatial variation of opportunity cost for commercial, non-commercial fishing, and aquaculture. Marxan conservation planning software was used to evaluate the comparative utility of two planning scenarios: (a) a whole-basin scenario, referring to selection of priority areas across the whole Mediterranean Sea, and (b) an ecoregional scenario, in which priority areas were selected within eight predefined ecoregions. Although both scenarios required approximately the same total area to be protected in order to achieve conservation targets, the opportunity cost differed between them. The whole-basin scenario yielded a lower opportunity cost, but the Alboran Sea ecoregion was not represented and priority areas were predominantly located in the Ionian, Aegean, and Adriatic Seas. In comparison, the ecoregional scenario resulted in a higher representation of ecoregions and a more even distribution of priority areas, albeit with a higher opportunity cost. We suggest that planning at the ecoregional level ensures better representativeness of the selected conservation features and adequate protection of species, functional, and genetic diversity across the basin. While there are several initiatives that identify priority areas in the Mediterranean Sea, our approach is novel as it combines three issues: (a) it is based on the distribution of habitats and not species, which was rarely the case in previous efforts, (b) it considers spatial variability of cost throughout this socioeconomically heterogeneous basin, and (c) it adopts ecoregions as the most appropriate level for large-scale planning.

Diet of the Monk Seal (Monachus monachus) in Greek Waters

Stomach contents were collected from 27 monk seal carcasses between 1997 and 2008 from different areas along the Greek coast. This sample included nine animals that had been deliberately killed and five accidental deaths due to fisheries interactions. Stomachs from monk seals of both sexes, including adults and subadults, were analysed. A total of 530 prey items from at least 71 prey species was identified, with approximately 74% of prey identified at least to genus, while 2.8% could be identified only to class level (i.e., fish or cephalopods). We found 266 cephalopods (50%), 253 fish (48%), a few non-cephalopod molluscs (1.5%), and two crustaceans (0.4%). Faecal samples were also collected but contained no identifiable prey remains. Octopuses were the most important prey in terms of numbers eaten and contribution to reconstructed prey biomass. The common octopus (Octopus vulgaris) (33.9% of prey by number) was around three times as numerous in the diet as the lesser octopus (Eledone cirrhosa) (11.1%). Fish of the families Sparidae (28.1%) and, to a lesser extent, Scorpaenidae (2.3%), Congridae (2.5%), and Atherinidae (2.5%) were also frequent in the stomachs. Many of the prey species recorded are of commercial fishery importance. Exploratory multivariate analysis (redundancy analysis [RDA]) indicated weakly significant seasonal, spatial, and interannual variation in diet and also suggested a relationship between diet composition and cause of death. No trends in diet related to sex or age class were identified. Sparids occurred more frequently in animals that had been deliberately killed than those that had died due to other causes, highlighting the interactions taking place between monk seals and fishing activities.

A Video Surveillance System for Monitoring the Endangered Mediterranean Monk Seal (Monachus monachus)

The components and specifications of a surveillance system developed in a pilot study to monitor Mediterranean monk seals (Monachus monachus) are presented. The system consisted of two B/W CCD cameras, infrared illuminators, a CCTV video web server, and photovoltaic solar panels, and it was operated under harsh outdoor conditions for three and a half months. It enabled the recording of rarely observed aspects of the Mediterranean monk seals’ social and reproductive behaviour, as well as provided a method to document demographic parameters of the local seal population. Advantages of the system include its non-invasive nature and its autonomous operation, while the primary disadvantage is the high initial cost, which should decrease as technology continues to improve. This system could prove to be a valuable tool in the conservation of critically endangered seal species such as the Mediterranean monk seal.

Report of a New Mediterranean Monk Seal (Monachus monachus) Breeding Colony in the Aegean Sea, Greece

Identifying and effectively protecting the last remaining Mediterranean monk seal (Monachus monachus) populations and their habitats is a key priority for the survival of this critically endangered species. Following the opening of a restricted naval area at the Island of Gyaros in the central Aegean Sea, Greece, the authors initiated efforts to verify the existence and assess the status of the species in the area. Using established monk seal habitat suitability criteria and survey techniques, the authors aimed to identify suitable habitat and document possible pup production of the species in this new area. Eight coastal caves were located throughout the coastline of the island, three of which were considered suitable for resting and pupping, while the remaining five were considered suitable for only resting. Pup production was recorded during the 2004, 2005, and 2007 pupping seasons, and a minimum of ten, four, and seven pups were identified, respectively. In addition, mother-pup associations and interactions on three open beaches, a behavior that has not been observed in this species in the Mediterranean Sea recently, were recorded. This newly discovered colony, with relatively high natality compared to other breeding sites in the Mediterranean Sea and the rare use of open beaches, is of outstanding conservation value and is in urgent need of effective protection.

First Observations of Parturition and Postpartum Behavior in the Mediterranean Monk Seal (Monachus monachus) in the Eastern Mediterranean

Understanding reproductive behavior, especially the circumstances surrounding parturition and the events following the first days postpartum, is essential in developing effective conservation strategies for endangered pinnipeds. In the case of the critically endangered Mediterranean monk seal (Monachus monachus), difficulties in documenting events such as parturition are compounded by the very low population numbers and the inaccessibility of the habitat occupied by the species. In this study, the authors report the first observations of parturition for the species from the central Aegean Sea, Greece, in the eastern Mediterranean Sea. Using a state-of-the-art infrared remotemonitoring system, two births were documented, and important information on the total duration of the events; the total duration of attempted suckling; as well as information on the presentation of the pups, their sex, and habitat were recorded. This new information on the reproductive biology of the species in this part of its range outline the importance of suitable reproductive caves for the conservation of the species and the urgency of protecting them. In addition, considering the high cost and logistics of the study, monitoring the species on a large scale to effectively protect it will require the development of new, low-cost, and time-efficient methodologies.

Assembling ecological pieces to reconstruct the conservation puzzle of the aegean sea

The effective conservation of marine biodiversity through an integrated ecosystem-based management approach requires a sound knowledge of the spatial distribution of habitats and species. Although costly in terms of time and resources, acquiring such information is essential for the development of rigorous management plans and the meaningful prioritization of conservation actions. Located in the northeastern part of the Mediterranean, the Aegean Sea represents a stronghold for marine biodiversity. However, conservation efforts are hampered by the apparent lack of spatial information regarding marine habitats and species. This work is the first to address this knowledge gap by assembling, updating, and mapping information on the distribution of key ecological components. A range of data sources and methodological approaches was utilized to compile and complement the available data on 68 ecological features of conservation interest (58 animal species, six habitat categories, and four other vulnerable ecological features). A standardized data evaluation procedure was applied, based on five semi-quantitative data quality indicators in the form of a pedigree matrix. This approach assessed the sufficiency of the datasets and allowed the identification of the main sources of uncertainty, highlighting aspects that require further investigation. The overall dataset was found to be sufficient in terms of reliability and spatiotemporal relevance. However, it lacked in completeness, showing that there are still large areas of the Aegean that remain understudied, while further research is needed to elucidate the distribution patterns and conservation status of several ecological features; especially the less charismatic ones and those found in waters deeper than 40 m. Moreover, existing conservation measures appear to be inadequate to safeguard biodiversity. Only 2.3% of the study area corresponds to designated areas for conservation, while 41 of the ecological features are underrepresented in these areas. Considering the high geomorphological complexity and transnational character of the Aegean Sea, this study does not offer a complete account of the multifaceted diversity of this ecoregion. Instead, it represents a significant starting point and a solid basis for the development of systematic conservation plans that will allow the effective protection of biodiversity within an adaptive management framework.

Stable Isotopes Confirm a Coastal Diet for Critically Endangered Mediterranean Monk Seals

Understanding the ecology and behaviour of endangered species is essential for developing effective management and conservation strategies. We used stable isotope analysis to investigate the foraging behaviour of critically endangered Mediterranean monk seals (Monachus monachus) in Greece. We measured carbon and nitrogen isotope ratios (expressed as δ13C and δ15N values, respectively) derived from the hair of deceased adult and juvenile seals and the muscle of their known prey to quantify their diets. We tested the hypothesis that monk seals primarily foraged for prey that occupy coastal habitats in Greece. We compared isotope values from seal hair to their coastal and pelagic prey (after correcting all prey for isotopic discrimination) and used these isotopic data and a stable isotope mixing model to estimate the proportion of coastal and pelagic resources consumed by seals. As predicted, we found that seals had similar δ13C values as many coastal prey species and higher δ13C values than pelagic species; these results, in conjunction with mean dietary estimates (coastal=61 % vs. pelagic=39 %), suggest that seals have a diverse diet comprising prey from multiple trophic levels that primarily occupy the coast. Marine resource managers should consider using the results from this study to inform the future management of coastal habitats in Greece to protect Mediterranean monk seals.

Aerial Vocalizations by Wild and Rehabilitating Mediterranean Monk Seals (Monachus monachus) in Greece

It is important that all aspects of the life history and behavior of Mediterranean monk seals (Monachus monachus) are documented to ensure effective management and conservation of this critically endangered species. Little is known about either airborne or underwater vocalizations for this species. Field research and rehabilitation of Mediterranean monk seal pups by MOm (MOm/Hellenic Society for the Study and Protection of the Monk Seal) provided opportunistic video recordings of the airborne sounds of this species. This study is the first to report acoustic features of airborne vocalizations from eight wild adult females and six of their pups, short-term recordings of a sick pup, and longer-term recordings of three rehabilitating pups. Although sample sizes are small, every effort was made to garner the most acoustic information from these recordings. The aims of this study were to document the acoustic properties and types of aerial vocalizations from wild and rehabilitating Mediterranean monk seals and to compare the acoustic features of their sound repertoire to the airborne vocalization characteristics of other monachids. Audio-tracks were spectrographically analyzed using six frequency and five time variables with Spectrogram software. Through examination of realtime spectrograms and audibly distinguishable characteristics, this study classified four airborne vocalization types (bark, snort, scream, and chirp) for adult females. Three aerial vocalization types (bark, gaggle, and squawk) were documented from pups. The bark was the most common vocalization type from wild and rehabilitating pups. Wild adult female Mediterranean monk seal vocalizations ranged in frequency from 438 to 3,050 Hz and consisted of 1 to 6 components within a series with a total duration from 42 to 8,171 ms. Airborne vocalization types of rehabilitating pups ranged in frequency from 269 to 1,584 Hz and consisted of 1 to 11 components within a series with a total duration from 88 to 12,006 ms. Using Pearson’s correlation analyses, many of the frequency and time variables were highly correlated. Principle Component Analysis (PCA), using nine variables, produced a 3-factor model that explained 98.8% of the variability in the acoustic features of the whole repertoire. A more parsimonious, 3-factor PCA model, using only six variables, still explained a high percentage of variability (81.5%). These results indicated that collecting only two frequency measurements (beginning frequency and first harmonic interval) and four time measurements (number of components within a series, total duration, component duration, and the component interval) is sufficient to distinguish among species-specific vocalizations. Results of this acoustical analysis are from a small number of Mediterranean monk seals, and further acoustic research is warranted to record adult males, and to increase the sample sizes of vocalizations from wild adult females and pups. In addition, more recordings of ill, stressed, and captive monk seals are needed. Lastly, vocalizations of wild Mediterranean monk seals should be studied at the other two main population sites (i.e., Archipelago of Madeira and Cabo Blanco region), at other times of the year, and outside of the breeding season to provide a better understanding of the overall vocal behavior of this species. The preliminary analyses presented herein hold promise that with sufficient data on acoustic features of airborne vocalizations researchers could acoustically monitor wild Mediterranean monk seals and determine their sex, pup age, and perhaps their health.

Trace element concentrations in the Mediterranean monk seal (Monachus monachus) in the eastern Mediterranean Sea

The Mediterranean monk seal (Monachus monachus) is one of the most endangered marine mammals in the world. The biggest sub-population of the species survives in Greece, where understanding the effects of pollution on the survival of the species has been identified as a national research and conservation priority. From 1990 to 2013 we collected tissue samples from 59 deceased monk seals in order to: (i) Define the concentration of trace elements (As, Pb, Cd, Hg, Se, Cr, Ni) in three different matrices (i.e., blubber, liver and kidney), (ii) Determine whether differences in trace element concentrations are age- or gender-related, (iii) Evaluate the potential effects of these pollutants. The study recorded differences in trace element concentrations among matrices, but in general, trace element exposure in Mediterranean monk seals in Greece was low and within the non-acutely toxic levels for Pinnipeds. Only arsenic concentrations were at the upper limit of the normal range observed in other marine mammals (0.69±0.55mg/kg w.w. in blubber, 0.79±0.62mg/kg w.w. in liver and 0.79±0.59mg/kg w.w. in kidney). We recorded also exceptionally high Hg concentrations in a single adult female (24.88mg/kg w.w.). Age- and gender-related differences were also recorded and were due to various biological, ecological and chemical factors. Based on the results of the study, potentially adverse effects on the immune and endocrine system of the Mediterranean monk seal from some pollutants (e.g., As, Cd, Se, Ni, Cr) cannot be ruled out, which may expose the Mediterranean seal population in Greece to epizootics and stochastic phenomena of mass mortality. It is therefore of utmost importance that pollutant monitoring becomes an integral component of the standard monitoring protocol of the endangered Mediterranean monk seal in the eastern Mediterranean.