## 4 Discussion  
The quantitative data were collected for the black scorpionfish using the same sampling methods and at comparable depths in two different areas located in coastal waters and with similar biotopes demonstrating variations in certain biological characteristics. They were found to occur at a finer spatial scale (about 200 km) in the eastern Adriatic Sea than has been shown elsewhere in the Mediterranean [10,15]. First of all, our results revealed spatial variation in length structure of _S. porcus_, as we found that smaller individuals caught in the Split area were more abundant than those caught in the Pag Island area. Length is a biological trait that responds to local conditions [39], so observed variation could be linked to some specific habitat characteristics. This is not unusual if we have in mind that _S. porcus_ has evolved high site fidelity [4]. In general, habitat characteristics are important in explaining local abundance patterns of benthic fish species, such as the investigated scorpionfish, but are difficult to control [7,40]. As well as influence on local fish abundance, habitat characteristics may also alter the patterns of distribution and abundance of different types of prey in the environment and consequently the relative abundance of prey taxa that are ingested by fish. This could account for our finding that the diversity of the food types ingested by the black scorpionfish in the Pag Island was greater than that of the same species in the Split area. In general, variations by area in the studies on fish diet are commonly related to differences in availability of resources in each area [41,42]. The findings on dietary compositions emphasize that in two different areas that were the subject of the present study, _S. porcus_ feeds on a wide variety of plant and animal taxa, as it does in areas elsewhere in the Mediterranean [6,12,13,14]. This, together with observed high selectivity for crustacean decapods, is a widespread feeding behavior in Scorpaenidae species in general [12]. The black scorpionfish ingested brown algae, spermatophytes, mollusks, arthropods, and fishes in both areas. However, within the major taxa, the contributions of the various dietary categories differed between areas. In terms of abundance, this scorpionfish consumed relatively more spermatophytes and arthropods in the Split area than in the Pag Island area, while specimens from the Pag Island area fed to a greater extent on other fishes. Moreover, Anomura (precisely _Porcellana longicornis_) and Brachyura (precisely _Xantho_ sp.) species were ingested in substantial amounts by _S. porcus_ in the Split area, and fishes from Pag Island consumed more Caridea (precisely _Processa edulis_) species. These data demonstrate that the black scorpionfish is a generalist and opportunistic feeder, which might have played an important role in the success of this species in a wide range of areas in the Mediterranean [43]. Furthermore, the statistical tests employed in this study emphasized that the dietary composition of _S. porcus_ in the Split area was significantly different from that in the Pag Island area. Two dietary categories, namely spermatophytes and fishes, were the most important of dietary categories for distinguishing between the diets of fish in the Split area from those in the Pag Island area. In addition, arthropods were also important in distinguishing the diet of _S. porcus_, so _Xantho_ sp. and an unidentified Brachyura species were contributors to the diet of this species in the Split area and Pag Island area, respectively. Such results, as previously mentioned and already documented for other fish species worldwide, could be related to variations in the spatial availability of the different types of prey in the environment [42]. The maximum age of _S. porcus_ estimated in this study was 12 years (fish from the Split area), being equal to the maximum age cited by [PERSON] et al. [15], using the same method and a similar fish length range.