Paraskevi K. Karachle

Morphometrics and Allometry in Fishes

Nowadays, the most commonly used relationships, that have been established for the majority of fishes (Binohlan & Pauly 2000, FishBase: www.fishbase.org: Froese & Pauly 2011), are those relating weight to body length (in the majority of cases, total body length (TL)), and different types of length (i.e., standard (SL) and fork (FL) length) to TL. Weight (W)-length (TL) relationships are of power type, i.e., W=a TLb. In this equation, a is the coefficient of body shape (Lleonart et al. 2000, Froese 2006, www.fishbase.org), and it gets values around 0.1 for fishes which are small sized and with a rounded body shape, 0.01 for streamlined-shaped fishes and 0.001 for eel-like shaped fishes. In contrast, b is the coefficient balancing the dimensions of the equation and its values can be smaller, larger or equal to 3 (Lleonart et al. 2000, Froese 2006, www.fishbase.org). In the first two cases (i.e., b 3) fish growth is allometric (i.e., when b 3 the fish grows faster in weigth than in length), whereas when b=3 growth is isometric. Froese (2006) analyze 3929 weight-length relationships for 1773 species, and reports that b ranges between 1.96 and 3.94, with 90% of the cases falling inside the 2.7-3.4 range. The lowest values have been recorded for Cepola macropthalma, whereas the highest for Chaenocephalus aceratus. In principle, these types of relationships are allometric (82%), with a trend towards positive allometry (Froese 2006). Weight-length relationships are of high importance for fisheries science and can be used in a wide range of applications, such as: (a) estimation of biomass from length data; (b) estimation of a species condition factor; and (c) comparisons among life history and morphologic differentiations of the same species in different areas (e.g., Pauly 1993, Petrakis & Stergiou 1995, Binohlan & Pauly 2000).

MOUTH ALLOMETRY AND FEEDING HABITS OF SOME MEDITERRANEAN FISHES

Feeding habits, diet composition, and food consumption in fishes have been related to various morphological characteristics notably the mouth (e.g., Karpouzi and Stergiou 2003), gut length (Kapoor et al. 1975, Kramer and Bryant 1995, Karachle and Stergiou 2010) and tail (Palomares and Pauly 1989, 1998, Pauly 1994, Karachle 2008). In particular, mouth shape and position, dentition, branchial spines (in terms of structure and number) and distance between gill rakers, and pharyngeal bone structure are strongly connected to species’ feeding and diet composition (Al-Hussaini 1947, Verigina 1991, Wootton 1998, Boyle and Horn 2006). Mouth gape is considered as an important, yet restraining, factor for food selection, capture, handling, and consumption (Keast and Webb 1966, Kapoor et al. 1975, Wainwright and Richard 1995, Karpouzi and Stergiou 2003, Makrakis et al. 2008, Goatley and Bellwood 2009). As fish grow, they tend to prey upon a greater size range of food items, and the mean size of the prey consumed increases, a fact more evident in second order carnivores and apex predators (Scharf et al. 2000, 2009, Stergiou and Karpouzi 2002, Karpouzi and Stergiou 2003, Arim et al. 2010). Such an increase in prey-size consumed is generally attributed to both morphological (e.g., ontogenetic mouth size increase) and physiological factors (e.g., vision acuity, increasing swimming ability), that allow predators to consume larger prey (Keast and Webb 1966, Kaiser and Hughes 1993, Juanes 1994, Juanes and Conover 1994, Hart 1997, Wootton 1998, Fordham and Trippel 1999). Therefore, and especially in carnivorous fishes, mouth shape and size can be used for the explanation of interACTA ICHTHYOLOGICA ET PISCATORIA (2011) 41 (4): 265–275 DOI: 10.3750/AIP2011.41.4.02

Feeding and ecomorphology of seven flatfish species in the North-North-West Aegean Sea, Greece

The diet composition and possible relationships between mouth area and intestine length with feeding were investigated for seven flatfish species in the North-North-West Aegean Sea. Samples were obtained from commercial fisheries (trawls and gillnets) on a seasonal basis, and a total of 444 individuals was analysed. The two most abundant species, Arnoglossus laterna and Citharus linguatula, preyed mainly on fish, and there were no differences in the feeding habits of the two species with season or sex. The remaining five species fed on small benthic invertebrates, mainly Crustacea and Polychaeta. Multivariate analysis showed that, based on their diet, the seven species formed three distinct groups. The mean mouth area and relative gut length differed significantly between the three groups, indicating differences in some of the morphological characteristics in order to avoid trophic overlap. The estimated trophic levels of these species (from 21 literature sources) ranged from 3.00 for Symphurus nigrescens to 4.49 for A. laterna and C. linguatula, indicating that flatfish span all trophic levels above 3.

Pescatourism A European review and perspective

Pescatourism is a relatively new concept of merging tourism with fi sheries. Its intention is to supplement incomes of fi shermen and their families in the situation of declining living resources of the sea and to provide an attractive activity for tourists visiting the sea coast. Pescatourism should be considered different activity from fi sheries tourism, or recreational fi shing (including charter fi shing), which usually denote angling. It also contributes to the education of the society and public awareness about the state and problems of the marine sector, including ecosystems, and experiencing the traditional fi shing culture. This new activity fi rst stared in Italy in 1982 and soon spread to other Mediterranean countries. Pescatourism can be considered a branch of sustainable tourism and an activity parallel to agrotourism. This essay provides an overview of pescatourism (and related activities) in European countries (Italy, France, Spain, Portugal, Greece, Cyprus, Germany) with additional examples from elsewhere. Chances for implementing pescatourism in other countries are analysed (Turkey, Algeria, Poland). Despite all these positive features, it can easily be a commercial activity which does not provide any benefi ts to fi shers and sustainability of marine living resources if the licence right is given to charter operators rather than to fishers.