Int. J. Aquat. Biol. (2021) 9(1): 23-32 ISSN: 2322-5270; P-ISSN: 2383-0956 Journal homepage: www.ij-aquaticbiology.com © 2021 Iranian Society of Ichthyology Original Article Population structure and dynamics of the invasive Procambarus clarkii (Girard, 1852) in a Tiber river Ramsar site, Central Italy Maxim Veroli* 1, Marco Martinoli1, Riccardo Caprioli2, Christian Angelici3, Domitilla Pulcini1, Fabrizio Capoccioni1 1Council for Agricultural Research and Economics (CREA), Research Centre for Animal Production and Acquaculture Via Salaria, 31, 00015 Monterotondo, Rome, Italy. 2ARPA Lazio, Regional Agency for Environmental Protection Via Giuseppe Saredo, 52, 00173, Rome, Italy. 3Regional nature reserve “Nazzano Tevere-Farfa”, S.P. Tiberina km 28,100, località Meana, 00060 Nazzano, Rome, Italy. s Article history: Received 18 September 2020 Accepted 17 January 2020 Available online 2 5 February 2021 Keywords: Crayfish Freshwater Invasive alien species Population dynamics Abstract: Procambarus clarkii is a native species of Central America, but strongly invasive in many regions of the world. An investigation on the red swamp crayfish was carried out to obtain more information about its population dynamics in the Tiber River, in Central Italy. A total of 900 individuals, both males and females, were sampled within two different campaigns (2017 and 2019) aimed at collecting biometric data. A strong fishing effort was deployed (more than 100 nets set), to guarantee a large and randomized number of samples. The crayfish populations were grouped into seven different cohorts, according to Bhattacharya’s method. The population showed a balanced sex ratio, the average cephalothorax length was 42.52 mm, with the most represented size class between 40-50 mm. K and L∞, as well as the growth parameter index (Ø), the mortality rate (Z), and longevity value (tmax), were calculated. K and Ø values resulted very high, showing an impressive growth rate in the study area; tmax ranged from 4 to 5 years, L∞ values were lower compared with other studies (58.0-59.0 mm), while Z was very high for this population (4.2-4.5 year). The results revealed that crayfish population dynamics can be complex and vary depending on habitat type, available trophic resource and competition. Introduction The red swamp crayfish, Procambarus clarkii Girard, 1852, is a native species of northeastern Mexico and southcentral USA. It is an r-selected species, which shows several invasive characteristics, such as rapid life cycle, strong dispersal capacity and high population densities. Therefore, it is able to colonize and disrupt a great variety of habitats, constituting a serious threat to the natural environment worldwide (Anastácio and Marques, 1997; Rodríguez et al., 2003, Souty-Grosset et al., 2016). Procambarus clarkii is considered among the 100 worst invasive species (Daisie, 2011) and it is listed in the “Union list” or “Black list” of invasive alien species (IAS), an important management tool included in the EU regulation 1143/2014 (EU, 2014). The main introduction agent of freshwater crayfish was farming activity and the hobby stand bait industry *Correspondence: Maxim Veroli DOI: https://doi.org/10.22034/ijab.v9i1.1006 E-mail: maxim_veroli@hotmail.it (Hänfling et al., 2011). Procambarus clarkii has been reported in several continents all over the world, and it represents so far as the second freshwater crayfish species more commercially farmed and more captured globally (Holdich, 1993; FAO 2020). In Europe, crayfish was legally imported from Louisiana for commercial purposes to Seville and Badajoz in 1973 (Habsburgo-Lorena, 1979). Later, the economic success of crayfish sale led to its illegal introductions in several European countries, even after the EU regulation 1143/2014, which banned its farming and sale (Chucholl, 2013). Due to the high dispersal capacity of this species, individuals started a rapid colonization throughout the Mediterranean basin and Central Europe (Anastácio and Marques, 1997; Barbaresi and Gherardi, 2000). Nowadays, P. clarkii is widespread and abundant all over Europe, including central and northern European countries 24 Veroli et al./ Population structure and dynamics of Procambarus clarkii (Louriero et al., 2015). This species represents a strong competitor and affects native freshwater species via direct predation on eggs, larvae, and juveniles and by competing with them for both resources and habitats (Gherardi, 2006). Moreover, digging activities of crayfish populations were demonstrated to affect river banks stability and to increase water turbidity (Rodriguez, 2005). Several studies highlighted the significant negative impacts of red swamp crayfish on natural ecosystems, which can be quantified in terms of ecosystem services (ES) loss. In particular, provisioning, regulatory and supporting services could be lost in freshwater habitats as a direct consequence of red swamp crayfish presence (Lodge et al., 2012). For instance, in Italy, where red swamp crayfish spread out in the 1990s, likely as a consequence of accidental release by some aquaculture farms in Piedmont (Del Mastro et al., 1992), P. clarkii threatened the native fauna (Barbaresi and Gherardi et al., 2001; Renai and Gherardi, 2004), altering the ecological community structure and reducing the food web complexity (Casellato and Masiero, 2011). These invasive ecological skills make P. clarkii an impressive competitor and a habitat destroyer, threatening local biodiversity through a direct impact and a decrease in the environmental quality parameters (Gherardi, 2006; Souty-Grosset, 2016). Crayfish activities affected both habitats used by fish for shelter or spawning and the whole aquatic ecosystem (Lodge et al., 2012; Souty-Grosset, 2016). Plant communities are altered both by direct consumption of macrophytes and by burrowing activities, responsible for shifts from clear water macrophyte-dominated areas to phytoplankton dominated areas (Rodríguez et al., 2003; Geiger et al., 2005; Matsuzaki et al., 2009). Procambarus clarkii activities are also believed to induce cyanobacteria blooms (Yamamoto, 2010). Threats and damages caused by red swamp crayfish are not only limited to freshwater communities but also extend to the coastal area, i.e. this species can invade the estuarine and brackish environments of the Adriatic coast as already reported for some Tyrrhenian areas (Scalici et al., 2010). In addition, groundwater native communities may be impaired by the presence of red swamp crayfish in the caves (Mazza et al., 2014). Here we provide a first study on the population structure of P. clarkii in the Regional nature reserve “Nazzano Tevere-Farfa”, an important wetland area of the Tiber river basin as one of Italian protected sites under the International Ramsar Convention (Carp, 1972). The site hosts fragile environments inhabited by species included in both European directives and the IUCN red list (Rondinini et al., 2013). This area needs, therefore, to be highly preserved and it is necessary to identify and characterize possible threats. Hence, the aims of the present study were to: (i) investigate the presence of crayfish in the study area, (ii) gather biological data about the local crayfish population and (iii) preliminary assess the red swamp crayfish population structure and dynamics in an important conservation site. This study will provide a major baseline for the future management and control of this invasive species. Materials and Methods This study was carried out along a stretch of the middle course of the Tiber River, within the Nature Regional Reserve of “Nazzano Tevere-Farfa” (Nazzano, Rome). The Reserve is 700 ha wide locating near the confluence of the Farfa Stream, 40 km northern Rome (42°12'N, 12°37'E), at an altitude about 30 m a.s.l. Since 1979, the site is protected according to the Ramsar Convention, the Birds Directive (European commission, 1979) and the Habitat Directive (EU, 1992). The site is also included in a Special Protection Area (SPA) and extends upstream of hydroelectric power station of “Nazzano”, including a section of the Tiber River up to the Poggio Mirteto mountain and a stretch of Farfa River up to Granica bridge. The area is composed by lotic faces, associated with the natural flow of the stream, and lentic faces, due to a dam construction. The core zone (Fig. 1) is located near the reserve center, within an area of about 15 ha with a maximum wet riverbed length of 420 m. Along the river shores, there are several small coves and islets characterized by reduced hydrodynamism and low 25 Int. J. Aquat. Biol. (2021) 9(1): 23-32 water depth (<1 m). Two sampling campaigns (22 samplings) were carried out in 2017 and 2019 (April-October). Sampling frequency was once a week and fixed traps (collapsible cylindrical traps, consisting of nylon threads of 1 cm mesh size with a length of 1 m and a 0.3 m mouth width) were used (Fig. 1). Each trap was baited with pork liver or with “caperlan” boiles. Ten series of fifteen linked-traps were prepared, randomly set in the area, and regularly moved to test the overall catchability in different zones inside the study area. Traps were placed in small coves, characterized by shallow, lentic and turbid water, and in running water, slightly deeper and cleaner, mostly near vegetated banks. Lentic water had a maximum depth of about 50 cm, whereas lotic water ranged from 40 to 100 cm. Water temperature was measured weekly. A subsample from total catches (about 50-60 individuals) was randomly selected to record biometric data. Cephalothorax length (CL; from the rostrum to the middle margin, to nearest 1 mm), weight (W; to nearest 1 g) and sex (S) were recorded on each specimen. CL was measured using a caliper, and the weight using a precision balance. Gender and female’s reproductive status (i.e. without eggs, eggs- carrying, and larvae-carrying) were recorded. Statistical analysis was performed in the R-Project environment (2.2.0 version), using “TropFishR” (Mildenberger et al., 2017) and “Flife” packages (Kell et al., 2016). Individuals were pooled in groups according to the month of capture, to reach a minimum number of observations (n>150; France et al., 1991) and to apply the Batthacharya method (Bhattacharya, 1967). Fishing selectivity on sex, for each year separately and for the overall fishing period, was determined by chi-squared test. Difference in sex ratio for each sampling group was tested using t-test. Von Bertalanffy equation (Von Bertalanffy, 1938) was used to assess crayfish growth, growth parameter index (Ø) and growth coefficient (k). CL data were used to generate 10 mm frequency distributions, which were analyzed through the Bhattacharya’s method, resulting in a yearly plot. The total mortality (Z) was estimated with the Powell-Wetherall Plot equation (Powell et al., 1979; Wetherall et al., 1986) by determination of L∞ (asymptotic CL) and Z/k, Figure 1. Map of the study area located within Natural Regional Reserve “Nazzano Tevere-Farfa”. Each point indicates the exact positions of crayfish traps used during both 2017 and 2019 sampling campaigns. 26 Veroli et al./ Population structure and dynamics of Procambarus clarkii using the length-frequency plot. The parameter k was also used to estimation of Z and calculated through the Electronic Length Frequency Analysis (Pauly and David, 1981; Taylor, Mildenberger, 2017) using an optimized approach based on simulated annealing (ELEFAN_SA) instead of the classical method based on the k-value scan method. Von Bertalanffy growth curve is described by the equation of Lt=L∞(1-e-k(t-t0)) (Von Bertalanffy, 1938); where k is the curvature of the function and it is needed to estimate the relative animal growth; t0 is the time 0, theoretical time at which individuals hatch while t is the time at this moment and L∞ is the asymptotic CL. In order to have an overview of the crayfish growth, also the growth parameter index (Ø) was estimated through the formula of Ø=ln K+2ln L∞ (Pauly and Munro, 1984). Finally, the value of age at time 0 (when crayfish have CL=0 mm) was assessed by the formula of ln(−t0)=− 0.3922–0.2752ln L∞−1.308ln K (Jin et al., 2019). While the expected longevity (tmax), derived from k value and t0, has been calculated as tmax=k(3+t0)-1 (Huang et al., 2012). Results During the study period (April-October), water temperature was 21-25°C and water depth of the sampling sites varied 40-180 cm. We analyzed a total of 900 crayfish, 441 males and 452 females, over a 2- year period. In 2017, we collected a total of 421 specimens (158 males and 263 females), and in 2019 472 (283 males and 189 females). Chi-squared test showed for the whole sample a 1:1 sex ratio (χ2 = 0.05, df=1, P>0.05), while in 2017 the ratio was in favor of females (χ2=26.188, df=1, P<0.05) compared to 2019, when we observed an opposite trend (χ2= 20.878, df=1, P<0.05). The average CL was 42.52 mm for the entire sample (42.52±0.96 mm), whereas in 2017 the mean value was 41.36 mm (41.36±0.93 mm; Fig. 2a) and in 2019, 43.69 mm (43.69±1.00; Fig. 2b). The most represented size class was 40-50 mm CL (n=255) for 2019 (n=154), while for 2017, it was 30-40 mm (n=105). Comparison between sexes of log- transformed CL data per sampling date did not show any significant difference (P>0.05). According to Bhattacharya’s procedure, both sex and years were separately analyzed (Fig. 3) to classify the collected crayfish into several age classes: for all year and sex, we found seven cohorts, except for September 2019 (6 cohorts) and also for females on 2017 (6 cohorts). Comparing the two sampling years, most represented classes showed different patterns: most crayfish of both sexes belonged to 30-40 mm class in July 2017, while in September males and females fell into 40-50 mm class. In April, males’ abundance was found in the sixth cohort (50-60 mm) while most of females fit in 40-50 mm length class. Concerning 2019, July and September listed in and, for both sexes, frequency peaks 40-50 mm in each month we recorded. Table 1. Growth parameters (k, Ø, L∞) and mortality rate (Z) values in different locations. Site Sex Type Habitat Origin Ø K L∞ Z Nazzano Tevere-Farfa Reserve (this study) M F Lotic River Creeks Main stream Natural 3.34 3.42 0.76 0.65 59.00 58.00 4.24 4.54 River Nile M F Lotic River delta Natural 3.20 2.70 - - - - 3.65 5.60 Delta del Pò M F Lotic Pond Natural - - 0.54 0.60 58.80 63.00 2.10 2.48 Qianjiang M F Lentic Swamp Artificial 8.01 7.97 0.81 0.86 60.93 58.12 2.32 1.93 Torre Flavia swamp M F Lentic Oligohalin Natural - - 0.32 0.33 68.30 74.60 2.99 4.71 Preola lake Reserve M F Lentic lakes Natural 3.19 3.19 0.34 0.35 68.25 67.20 3.43 3.83 Trasimeno lake M F Lentic Shallow Lake Natural - - 0.59 0.58 69.35 73.71 5.50 5.10 Circeo National Park M F Lentic Coastal lake Natural - 0.66 0.70 64.30 63.30 3.43 4.07 27 Int. J. Aquat. Biol. (2021) 9(1): 23-32 Figure 2. Mean and standard deviation of the cephalothorax length (CL) recorded during field samplings grouped by year (2017, 2019) and gender (females and males). Figure 3. Length-frequency distributions calculated by ELF (Electronic Length Frequency) analysis that uses an optimized approach based on simulated annealing (ELEFAN_SA). 28 Veroli et al./ Population structure and dynamics of Procambarus clarkii Table 1 reported growth parameters (k and L∞), growth parameter index (Ø), and mortality rate (Z) for both years. Values in Table 1 were calculated for both sexes and years. Longevity values (tmax) ranged from 4 to 5 years: the highest longevity was recorded in 2019 for males (4.9 years), while the lowest value was recorded in 2019 for females (4.3 years old). In 2017, similar values, of about 4.5 years old, were recorded. Discussions This study investigated the characteristics of the invasive red swamp crayfish in the Regional Nature Reserve of “Nazzano Tevere-Farfa”, an important biodiversity hotspot of Central Italy. First reports of the presence of the red swamp crayfish in the Tiber River in Latium date back to 1997 at the Castel Giubileo dam (Giucca, 1997), about 40 km below the Nature Reserve. This alien species may be very dangerous for the maintenance of ecosystem balances of vulnerable habitats such as freshwater ones. We analyzed a total of 900 specimens in order to gather information about population structure and dynamics, that could be useful for future management actions on P. clarkii population of the reserve. The majority of analyzed crayfish were adult (CL>20 mm), likely as a consequence of the fishing gear selectivity (10 mm wide), that only allows the capture of larger individuals. The population was composed of crayfish aged at least 2+ (20 mm4 years) is one of the highest ever recorded. The population studied is located in the middle stretch of the Tiber River, a lotic environment characterized by slow, shallow and productive waters. Hence, the study area could be ecologically compared to those where crayfish showed high Z values, such as the Nile river (Saadet al., 2015) and Trasimeno lake (Dorr and Scalici, 2013). The river confluence area of the 29 Int. J. Aquat. Biol. (2021) 9(1): 23-32 “Nazzano Tevere-Farfa” Nature Reserve is highly productive due to the large amount of terrigenous contributions and low water flow (Nijboe and Verdonschot, 2004). In addition, the river forms some islets that increase habitat diversity and shelters. This environment was created in the 1950s, immediately after the construction of a hydroelectric dam (unpublished data, 1950). Landscape transformation brought to a deep alteration of physical characteristics, such as oscillation of water level, increase of external inputs and the consequent increase of trophic conditions (Baxter, 1977), influencing biological communities. Local crayfish population found in this area the ideal conditions that allow high density, fast growth rate and longer life span (Momot et al., 1978; Jackson et al., 2017). Our findings may infer some considerations about crayfish spawning period. Since water temperature plays an important role in crustacean reproduction (Huner, 2002; Alcorlo et al., 2008; Jin et al., 2019), in southern Mediterranean permanent water bodies, spawning may take place even twice a year, in spring and autumn (Scalici and Gherardi, 2007; Alcorlo et al., 2008; Dörr and Scalici, 2013). This phase usually takes place in late summer and presents a variable duration, mostly dependent on water temperature, food resources and habitat (Huner, 2002; Alcorlo et al., 2008; Jin et al. 2019). During samplings, we observed ovigerous females only in the autumnal period (September/October), as already observed in similar studies (Dörr et al., 2006; Jin et al., 2019; Mistri et al., 2019). As aforementioned, the number of spawning crayfish events is mostly related to water temperature and therefore it is linked to local climatic and environmental factors (Jin et al., 2019). Therefore, we can speculate that the peculiar characteristics of the study area allow the crayfish population to have only one autumnal spawning period. Conclusion In this study, we found a consistent presence of Procambarus clarkii, which colonizes the whole study area. The good health of the studied population, characterized by balanced sex ratio and rapid growth, suggests the need of an effective action plan aimed at rapidly mitigating and remediating the negative impacts of this invasive species. Acknowledgements This study was part of a larger research project supported by Ager foundation (project SUSHIN n°0112-2016). The Authors are grateful to the "Nazzano Tevere-Farfa" Regional nature reserve, which permitted to carry out scientific samplings. References Alcorlo P., Geiger W., Otero M. (2008). Reproductive biology and life cycle of the invasive crayfish Procambarus clarkii (Crustacea: Decapoda) in diverse aquatic habitats of South-Western Spain: Implications for population control. Fundamental and Applied Limnology, 173(3): 197-212. Anastacio P.M., Marques J.C. (1995). Population biology and production of the Red Swamp Crayfish Procambarus clarkii (Girard) in the Lower Mondego River Valley, Portugal. Journal of Crustacean Biology, 15(1): 156. Anastácio P.M., Marques J.C. (1997). Crayfish, Procambarus clarkii, effects on initial stages of rice growth in the lower Mondego River valley (Portugal). Freshwater Crayfish, 11: 608-617. Barbaresi S., Gherardi F. (2000). The invasion of the alien crayfish Procambarus clarkii in Europe, with particular reference to Italy. Biological Invasions, 2(3): 259-264. Baxter R.M. (1977). Environmental effects of dams and impoundments. Annual Review of Ecology and Systematics, 8(1): 255-283. Carp E. (1972). In: Proceedings of the international conference on the conservation of wetlands and waterfowl—Ramsar, Iran, 30 January–3 February 1971. Slimbridge, UK: International Wildfowl Research Bureau. 303 p. Casellato S., Masiero L. (2011). Does Procambarus Clarkii (Girard, 1852) Represent a threat for estuarine brackish ecosystems of Northeastern Adriatic Coast (Italy)? Journal of Life Sciences, 5: 549-554. Chiesa S., Scalici M., Gibertini G. (2006). Occurrence of allochthonous freshwater crayfishes in Latium (Central Italy). Bulletin France Peche Pisciculture, 380-381: 883-902. Chucholl, C. (2011). Disjunct distribution pattern of 30 Veroli et al./ Population structure and dynamics of Procambarus clarkii Procambarus clarkii (Crustacea, Decapoda, Astacida, Cambaridae) in an artificial lake system in Southwestern Germany. Aquatic Invasions, 6(1): 109- 113. Chucholl C. (2013). Invaders for sale: trade and determinants of introduction of ornamental freshwater crayfish. Biological Invasions, 15: 125-141. Correia A.M. (2002). Niche breadth and trophic diversity: feeding behaviour of the red swamp crayfish (Procambarus clarkii) towards environmental availability of aquatic macroinvertebrates in a rice field (Portugal). Acta Oecologica, 23(6): 421-429. Daisie (2011). European invasive alien species gateway. One hundred of the worst. http://www.europe aliens.org/speciesTheWorst.do. Del Mastro G.B. (1992). Sull’acclimatazione del gambero della Louisiana Procambarus clarkii (Girard, 1852) nelle acque dolci italiane (Crustacea: Decapoda: Cambaridae). Pianura, 4: 5-10. Directive E.C.H. (1992). Habitat Directive. Environment Directorate-General: Council Directive 92/43/EEC of 21 May 1992 on the Conservation of Natural Habitats and of Wild Fauna and Flora. Official Journal, L. 206: 7. Dörr A.J.M., La Porta G., Pedicillo G., Lorenzoni M. (2006). Biology of Procambarus clarkii (Girard, 1852) in Lake trasimeno. In: BFPP – Bulletin Francais de la Peche et de la Protection des Milieux Aquatiques. pp: 1155-1167. Dörr A.J.M., Scalici M. (2013). Revisiting reproduction and population structure and dynamics of Procambarus clarkii eight years after its introduction into Lake Trasimeno (Central Italy). Knowledge and Management of Aquatic Ecosystems, 408: 10. EU (2002). Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora. Official Journal. 206 p. European Community (1979). Council Directive of 2 April 1979 on the conservation of wild birds (79/409/EEC). Official Journal of the European Communities, 94(103): 18. European Union (2014). Invasive alien species. Kerstin Sundseth, Ecosystems LTD, Brussels under service contract N(0307/2012/633322/SER/B3. 28 p. FAO (2020). Fisheries and aquaculture software. FishStat Plus - Universal software for fishery statistical time series Version 2.3. (Fisheries Department, Fishery Information, Data and Statistics Unit, Rome, 2020). http://www.fao.org/fishery/ France R., Holmes J., Lynch A. (1991). Use of size- frequency data to estimate the age composition of crayfish population. Canadian Journal of Fisheries and Aquatic Science, 48: 2324-2332. Geiger W., Alcorlo P., Baltanas Montes C. (2005). Impact of an introduced crustacean on the trophic webs of Mediterranean wetlands. Biological Invasions, 7: 49-73. Giucca F. (1997). Nuove segnalazioni relative all’ittiofauna del tratto urbano del fiume Tevere (Roma). Atti del I° Convegno Nazionale Sulla Fauna Urbana, Roma. pp: 127-129. Hänfling B., Edwards F., Gherardi F. (2011). Invasive alien Crustacea: Dispersal, establishment, impact and control. BioControl, 56: 573-595. Holdich, D.M. (1993). Une synthèse de l’astaciculture: L’élevage d’écrevisse en eau douce. Aquatic Living Resources, 6(4), 307-317. Huang Y., Wang S.J., Dai Y.G., Fang C.L., Xiao M.H., Wang J.M., Hu C.Y. (2012). Sustainable yield of the red swamp crayfish (Procambarus clarkii) through understanding its population structure and dynamics in Poyang Lake. Crustaceana, 85(4-5): 415-431. Jackson M.C., Evangelista C., Zhao T., Lecerf A., Britton J.R., Cucherousset J. (2017). Between-lake variation in the trophic ecology of an invasive crayfish. Freshwater Biology, 62(9): 1501-1510. Kell L., Mosqueira I., Fromentin J.M. (2016). FLife: An R Package for modelling life history relationships and dynamic processes. ICCAT Collect, Vol. of Science. 73 p. Gherardi F., Renai B., Corti C. (2001). Crayfish predation on tadpoles: a comparison between a native (Austropotamobius pallipes) and an alien species (Procambarus clarkii). Bulletin Français de la Pêcheet de la Pisciculture, 361: 659-668. Gherardi F. (2006). Crayfish invading Europe: the case study of Procambarus clarkii. Marine and Freshwater Behaviour and Physiology, 39(3): 175-191. Gherardi F. (2007). The impact of freshwater NIS: what are we missing? In: F. Gherardi (Ed.) Biological Invaders in Inland Waters: Profiles, Distribution, and Threats. Invading Nature: Springer Series in Invasion Ecology. Springer, Dordrecht, The Netherlands. pp: 437-462. Habsburgo-Lorena A.S. (1972). Crayfish situation in Spain. Crayfish News, 3(2): 1-2. Huner J.V. (2002). Procambarus. In: D. Holdich (Ed.). Biology of Freshwater Crayfish. Blackwell Science 31 Int. J. Aquat. Biol. (2021) 9(1): 23-32 Ltd., Oxford. pp: 541-584. Jin S., Jacquin L., Xiong M., Li R., Lek S., Li W., Zhang T. (2019). Reproductive pattern and population dynamics of commercial red swamp crayfish (Procambarus clarkii) from China: Implications for sustainable aquaculture management. PeerJ, 1. 10.7717/ peerj.6214. Loureiro T.G., Anastácio P.M.S.G., Araujo P.B., Souty- Grosset C., Almerão M.P. (2015). Red swamp crayfish: biology, ecology and invasion - an overview. Nauplius, 23(1): 1-19. Lodge D.M., Deines A., Gherardi F., Yeo D.C.J., Arcella T., Baldridge A.K., Barnes M.A., Lindsay Chadderton W., Feder J.L., Gantz C.A., et al. (2012). Global introductions of crayfishes: Evaluating the impact of species invasions on ecosystem services. Annual Review of Ecology, Evolution, and Systematics, 43(1): 449-472. Maccarrone V., Filiciotto F., Buffa G., Di Stefano V., Quinci E.M., de Vincenzi G., Mazzola S., Buscaino G. (2016). An invasive species in a protected area of Southern Italy: The structure, dynamics and spatial distribution of the crayfish Procambarus clarkii. Turkish Journal of Fisheries and Aquatic Sciences, 16: 401-412. Matsuzaki S.I.S., Usio N., Takamura N., Washitani I. (2007). Effects of common carp on nutrient dynamics and littoral community composition: Roles of excretion and bioturbation. Fundamental and Applied Limnology, 168(1): 27-38. Mazza G., Reboleira A.S.P.S., Alves F.G., Aquiloni L., Inghilesi A.F., Spigoli D., Stoch F., Taiti S., Gherardi F., Tricarico E. (2014). A new threat to groundwater ecosystems: First occurrences of the invasive crayfish Procambarus clarkii (Girard, 1852) in European caves. Journal of Cave and Karst Studies, 76: 62-65. Mildenberger T.K., Taylor M.H., Wolff M. (2017). TropFishR: An R package for fisheries analysis with length-frequency data. Methods in Ecology and Evolution, 8(11): 1520-1527. Mistri M., Sfriso A., Sfriso A.A., Munari C. (2019). Distribution and population structure and dynamics of the red swamp crayfish Procambarus clarkii (Girard, 1852) in the eastern Po valley and its delta (Northeastern Italy). BioInvasions Records, 8(1): 142-153. Momot W.T., Gowing H., Jones P.D. (1978). The Dynamics of Crayfish and Their Role in Ecosystems. American Midland Naturalist, 99(1): 10. Nijboer R.C., Verdonschot P.F. (2004). Variable selection for modelling effects of eutrophication on stream and river ecosystems. Ecological Modelling, 177(1-2): 17- 39. Pauly D., David N. (1981). ELEFAN I A basic program for the objective extraction of growth parameters from length frequency data. Meeresforschung, 28(4): 205- 211. Pauly D., Munro J.L. (1984). Once more on the comparison of growth in fish and invertebrates. Fishbyte, The WorldFish Center, 2(1): 1-21. Powell D.G. (1979). Estimation of mortality and growth parameters from the length frequency of a catch [model]. Rapports et Proces-Verbaux des Reunions, 175: 167-169. Renai B., Gherardi F. (2004). Predatory efficiency of crayfish: comparison between indigenous and nonindigenous species. Biological Invasions, 6: 89-99. Reynolds J., Souty-Grosset C. (2011). Management of freshwater biodiversity: Crayfish as Bioindicators. Cambridge University Press, Cambridge. 398 p. Rodríguez C.L., Bécares E., Fernández-Aláez M. (2003). Shift from clear to turbid phase in Lake Chozas (NW Spain) due to the introduction of American red swamp crayfish (Procambarus clarkii). Hydrobiologia, 506: 421-426. Rodríguez C.F., Bécares E., Fernández-Aláez M., Fernández-Aláez C. (2005). Loss of diversity and degradation of wetlands as a result of introducing exotic crayfish. Biological Invasions, 7(1): 75-85. Rondinini C., Battistoni A., Peronace V., Teofili C. (2013). Lista Rossa IUCN dei Vertebrati Italiani. Comitato Italiano IUCN e Ministero dell’Ambiente e della Tutela del Territorio e del Mare, Roma. RStudio Team (2015). RStudio: Integrated Development for R. RStudio, Inc., Boston. Saad A., Mehanna S., Khalil M. (2015). Population Dynamics of the Freshwater Crayfish Procambarus Clarkii (Girard, 1852) in the River Nile, Egypt. Egyptian Journal of Aquatic Biology and Fisheries, 19: 101-116. Scalici M., Gherardi F. (2007). Structure and dynamics of an invasive population of the red swamp crayfish (Procambarus clarkii) in a Mediterranean wetland. Hydrobiologia, 583: 309-319. Svedäng H., Hornborg S. (2014). Selective fishing induces density-dependent growth. Nature Communications, 5(4):152. 32 Veroli et al./ Population structure and dynamics of Procambarus clarkii Souty-Grosset C., Anastácio P.M., Aquiloni L., Banha F., Choquer J., Chucholl C., Tricarico E. (2016). The red swamp crayfish Procambarus clarkii in Europe: Impacts on aquatic ecosystems and human well-being. Limnologica, 58: 78-93. Taylor M.H., Mildenberger T.K. (2017). Extending electronic length frequency analysis in R. Fisheries Management and Ecology, 24(4): 230-238. Ulmestrand M. (2001). Growth of Norway lobster, Nephrops norvegicus (Linnaeus 1758), in the Skagerrak, estimated from tagging experiments and length frequency data. Ices Journal of Marine Science, 58: 1326-1334. Von Bertalanffy L. (1938). A quantitative theory of organic growth (inquiries on growth laws II). Human Biology, 10(2): 181-213. Wetherall J.A. (1986). A new method for estimating growth and mortality parameters from length-frequency data. ICLARM Fishbyte, 4: 12-14. Yamamoto Y. (2010). Contribution of Bioturbation by the Red Swamp Crayfish Procambarus Clarkii to the recruitment of bloom-forming cyanobacteria from sediment. Journal of Limnology, 69(1): 102-111.