An Assessment of Snail-Farm Systems Based on Land Use and Farm Components

Simple Summary This study’s goal was a thorough analysis and a detailed characterization of commercial snail farms in Greece, considering the unstructured development of the snail-farming sector over recent years. Additionally, the characterization of snail farms in Greece could help Southern European countries improve heliciculture. This study classifies 29 farms in five snail farming systems: elevated sections (7%), net-covered greenhouse (38%), a mixed system with a net-covered greenhouse (10%), open field (38%), and mixed system with an open field (7%). Results showed the impact of various parameters (farming system, region, equipment, and facilities) on annual production. Snail farms were dispersed in six different regions (Thrace, Central Macedonia, West Macedonia, Thessaly, Western Greece, and the Attica Islands). The location affected productivity, but also influenced the duration of operation during an annual cycle. Abstract In this study, the structural and management characteristics of snail farms in Greece were analyzed to maximize sustainable food production. Objectives, such as the classification of farming systems and assessing the effects of various annual production parameters, were investigated. Data were collected (2017) via a questionnaire, and sampling was conducted in 29 snail farms dispersed in six different regions (Thrace, Central Macedonia, West Macedonia, Thessaly, Western Greece, and the Attica Islands). Descriptive statistics for continuous variables and frequencies for categorical variables were calculated. The similarity between farms was analyzed using nonmetric multidimensional scaling (nMDS). The average farm operation duration exceeded eight months and the mean annual production was 1597 kg of fresh, live snails. Results recorded five farming systems: elevated sections (7%), net-covered greenhouse (38%), a mixed system with a net-covered greenhouse (10%), open field (38%), and mixed system with an open field (7%). Snail farms differ in the type of substrate, available facilities, and equipment (60% similarity between most of the open field farms). The geographical location of a farms’ settlement affects productivity but also influences the duration of operation, especially in open field farms, due to their operation under a wide assortment of climatic types.


Introduction
Heliciculture has been practiced since the 1st century BC. Nowadays, commercial snail farms have been established in many parts of the world. Simultaneously, extensive and intensive farming methods have been developed [1][2][3]. Terrestrial gastropods are a high-value food product and a source of special byproducts (caviar, mucus, and bioactive substances) with great commercial value [4,5]. In recent years, in the dermatological sector, there has been an increase in the use of snail extract (e.g., in management of burns) as it has exhibited therapeutic, sedative, and anti-aging properties [4,5]. Universally, consumable the production practices of heliciculture. This study's goal was a thorough analysis and a detailed characterization of commercial snail farms in Greece, considering the unstructured development of the snail-farming sector over recent years [10,11]. The classification of the farms is important to identify aspects of production that require improvement. Additionally, snail farms' characterization in Greece could help Southern European countries improve heliciculture [2,[30][31][32]. We aimed to effectively describe snail farming systems in Greece to produce a significant insight into the sector's current status. In addition, we assessed the effects and impacts of various parameters (farming system, region, equipment, and facilities) in annual productivity using a questionnaire developed to assess the farms' structural and administration characteristics. This allowed the identification of specific farm components that require alteration and/or improvement in order to achieve profitable management. This study is the first step for establishing strategic planning policies for the sustainable development of snail farming.

Area of Experiment
The present research was conducted on 29 snail farms located in six regions (Central Macedonia, West Macedonia, Thessaly, Thrace, Western Greece, and Attica-Islands) in Greece ( Figure 1). The climate in these regions is of the Mediterranean type with continental influence in some areas [33]. A widespread report of snail-farm systems and their attributes were collected through a designated questionnaire, holding visitations, and snail sampling.

Data Collection
Data were gathered with the use of a structured questionnaire through face-to-face interviews with snail producers. The duration of each interview was 2-3 h and each interviewee completed open-ended and closed questions. Data on management practices, technical characteristics, financial data, and production chain were collected. For the compilation of the questionnaire, related surveys [9,10,28,34] were considered, adapted to the current study's requirements.
The data collected included seven main topics, further divided into sub-categories, the most important of which are: (a) Owner (Farmer's experience, Farmer's age), (b) Livestock (farmed snail species, snail weight, number of snails/kg, growth rate, mortality rate), (c) Production (farm production, productivity per beneficial surface), (d) Land (altitude, farming area, beneficial surface, substrate, plants), (e) Management and Nutrition (duration of operation, duration of reproduction period, rearing duration, starting period, harvest period, feed quantity, feeding frequency, use of cooling system, and shade rate of net), and (f) estimated income. Finally, questions (g) about farming type, equipment, and facilities were included in the survey.
Additional information was collected on each snail farm's type of substrate and the use of growth rate indicators. A snail farm substrate included soil with planted broadleaf plants and gravel or soil without a plant presence. Substrate and diet were clustered on two categories: (a) type of substrate and (b) type of diet. More specifically, the substrate cluster included sub-clusters for (G-gravel, P-soil with cultivated plants, and S-soil). The later cluster included sub-clusters for diet types: (c-compound diet, cp-compound diet and plants, and p-plants). Growth rate indicators were used to detect possible effects of certain factors with daily fluctuation, such as climatic parameters (temperature, humidity, rainfall) on snail size. The presence of certain facilities (harvest warehouse, hatchery, packaging laboratory, and cooling chamber) and equipment (fabric for low temperatures, cages, tatters, egg storage containers, hibernation chamber, temperature sensors, humidity sensors, packaging materials, and agricultural tools) were evaluated either as existing or absent.

Sampling Procedures
The sampling period lasted from June to November 2017. In each farm, one sampling took place and 3 kg of commercial sized snails were collected in order to assess productivity components. Snails were numbered and weight was measured individually. The long sampling period is based on the necessity that snails in each farm must reach a marketable size. The produced snail species are Cornu aspersum maximum (syn. Helix aspersa maxima, common name "gros gris") and Cornu aspersum aspersum (syn. Helix aspersa, common name "petit gris"). Each snail species' marketable size was determined from the data received through the questionnaires (6 g for Cornu aspesum aspersum and 12 g for Cornu aspersum maximum).

Statistical Analysis
Initially, descriptive statistics (mean, median, standard deviation, and standard error) for continuous variables and frequencies for categorical variables were calculated. Thereafter, four original variables were selected (farming system, region, species, and substrate) and were used as factors to estimate their influence on three productivity variables (FP, Farm Production in kg × year −1 , PS, Productivity per surface in kg × (m 2 ) −1 × year −1 and PB, Productivity per beneficial surface in kg × (m 2 ) −1 × year −1 ). Descriptive statistics were calculated, and the main effect plots were presented. The small sample size justified the use of this statistical method.
For categorical variables, nonmetric Multidimensional Scaling (nMDS), based on the Bray-Curtis similarity index using the Unweighted Pair Group Method with Arithmetic mean (UPGMA) [35], was used as a means of visualizing the percentage of similarity between different farms. The percentage of similarity between farms was analyzed using cluster analysis based on the Bray-Curtis similarity index [36]. To normalize data and avoid skewness, a fourth root transformation was applied to the data prior to calculating similarities [37]. Data analysis was performed with the PRIMER package [38] (PRIMER-e, Auckland, New Zealand).
In order to estimate the potential income of snail farmers, total farm production (kg × year −1 ) was calculated with the price of 5 € per kg of fresh live snails, which is the current market price in Greece according to information collected through the questionnaires, which is in agreement with recent literature [10].

Snail Farm Attributes
The average values for the structural and management characteristics for the total sampled snail farms are presented in Table 1. The snail farms' average land was 3838 m 2 , comprised of 2593 m 2 of the beneficial area and 1250 m 2 of a non-beneficial area ( Table 1). The farm installed at the highest altitude (759 m) above sea level was in Western Macedonia, while in Western Greece, a farm is located at sea level. The average farm operation duration exceeded eight months and the mean annual production was 1597 kg of fresh live snails (Table 1). Most farmers belong to 30-40 years old (45%) and have obtained a degree from a higher education institution (77%). Heliciculture is not their only income source, as an overwhelming percentage (87%) has a second occupation. The longest farmers' experience was five years (Table 1).

Farming Systems
Snail farming systems can be held in open field farms or covered constructions of different types. Apart from the two systems above, the present study recorded three categories of farming systems. Thus, five clusters were created with the following characteristics ( Table 2). Table 2 indicates that Greece's most widespread systems are the net-covered greenhouse (38%) and the open field (38%). On the contrary, the least common systems are the mixed system with an open field and the elevated sections (7%). Open-field system farms are mainly located in West Macedonia (45%). The majority of net-covered greenhouses are found in Central Macedonia (45%), while several operate in Thessaly (27%).
From the 29 farms surveyed, 25 use Cornu aspersum maximum as their farmed species, whereas two farms use Cornu aspersum aspersum. Two farms culture both species ( Table 2). The annual production process includes reproduction of the mature snails, hatching of eggs, and increase of hatchlings as well as fattening of snails. After the fattening is completed, snails are harvested.
Mixed systems with a net-covered greenhouse had the smallest available farming areas ( Table 3). As far as altitude is concerned, elevated sections and net-covered greenhouses are higher than the other three types (Table 3). Regarding productivity (snails/kg), three types of farms are similar (elevated sections, a mixed system with a net-covered greenhouse, and a mixed system with an open field). The growth rate ranged between 0.09 and 0.15 gr × day −1 × snail −1 (Table 3). In the section of management, the duration of operation decreases in open fields (Table 3). In farm types with a net, it reaches up to nine months. In addition, the duration of the reproduction period has the same pattern (Table 3). In most of the farms, March was the starting month, while harvest took place in November.  Table 3. Mean value ± standard deviations (S.D.) for continuous variables in every farming system.

(n = 2) 2 (n = 11) 3 (n = 3) 4 (n = 11) 5 (n = 2)
Attributes Mean Mean ± SD Mean ± SD Mean ± SD Mean In total, 65% of snail farmers used a compound diet for snails, together with existing plants (Figure 2). The combination of a compound diet with plants was the most common diet in every farm type. Feeding only with plants appeared in one open farm ( Figure 2). As a substrate for farmed snails, soil with cultivated broadleaf plants was mostly used (77%), along with gravel, exclusively in some net-covered greenhouses or soil without the presence of plants (Figure 2). Soil and gravel were only present in net-covered greenhouses or a mixed system with a net-covered greenhouse (Figure 2). In Table 4, frequencies of facilities and equipment of different types are presented. Almost every snail farm has a harvest warehouse. Hatcheries were found only in mixed system farms (Table 4). Packaging stations and cooling chambers were not present in the minority of the farms (Table 4). Table 4. Frequencies for categorical variables (facilities and equipment) in every farming system.

Production Variables
The descriptive statistics and the main effects plot of each factor's influence (species, substrate type, farm type, and region) exerts on farm production (kg × year −1 ) are presented in Table 5 and Figure 4, respectively.    Figure 5 indicate that the mean productivity per surface (kg × (m 2 ) −1 × year −1 ) decreases from elevated sections to the mixed system with an open field. Regarding the region, data are grouped in three different clusters: regions 5 and 6 (Attica Islands and Western Greece) with high production, regions 1 and 3 (Thessaly and Central Macedonia) with medium production, and regions 2 and 4 (West Macedonia and Thrace) with low production (Table 6, Figure 5). It should be noted that all farms present in regions 5 and 6 are covered (three net-covered greenhouses and one with elevated sections). Furthermore, in Southern Greece (Attica), farms operate from February to November, whereas, in Northern Greece (Thrace), the operation starts in April or even in May. West Macedonia and Thrace farms operate for a shorter period throughout the year. In addition, an important fact is that seven out of eight farms located in these regions are the open field type.   Mean production per beneficial surface (kg × (m 2 ) −1 ) × year −1 ) in Table 7 follows the same pattern as the productivity per surface for all factors. The difference, however, is that each value is higher ( Figure 6).

Discussion
The current study indicated that the average snail farmer's age is 44.5 years with only five to six years of experience in this field. Heliciculture is not their only income source, as an overwhelming percentage (87%) has a second occupation. This result can be attributed to the fact that snail farming is a relatively new livestock industry sector [10,11]. The average land that snail farms occupy was 3838 m 2 , comprised of 2593 m 2 beneficial areas and 1250 m 2 non-beneficial areas. According to the latest available data from the Greek Ministry of Rural Development and Food [11], snail farms' average size is small (8200 m 2 for the open farms and 1800 m 2 for the net-covered greenhouses), while very few have a size larger than 15,000 m 2 . The average farm operation duration exceeded eight months, and the mean annual production was 1597 kg of fresh live snails. Similar to other European countries [8,14,32], the main species produced in Greece are Cornu aspersum aspersum and Cornu aspersum maximum, which are both of a recognized commercial value [5,7,8,10,11,15].
This study classified 29 commercial snail farms in Greece and described them in detail (typology). The outcome indicated that heliciculture exhibits various classification schemes from extensive of small demand to intensive of high producing and investing farms. The present study recorded five farming systems, namely elevated sections (intensive), netcovered greenhouse (intensive), a mixed system with a net-covered greenhouse (intensive), an open field (extensive), and a mixed system with an open field (semi-intensive). Some have been described in previous studies [10,15]. Greece's most widespread systems are the net-covered greenhouse (38%) and the open field (38%). Most of the net-covered greenhouses are found in Central Macedonia (45%), and are followed by Thessaly (27%). Open field farms are mainly located in West Macedonia (45%). A mixed system with an open field has the lowest production (528.5 kg × year −1 ) while the other systems' production is similar. Annual farm production is directly related to the size of the fattening area. Although, the productivity per surface seems to decrease from elevated sections (2.04 kg × (m 2 ) −1 × year −1 ) to the mixed system with an open field (0.067 kg × (m 2 ) −1 × year −1 ). Finally, higher values were obtained for productivity per beneficial surface (maximum 4.077 kg × (m 2 ) −1 × year −1 for elevated sections and minimum 0.101 kg × (m 2 ) −1 × year −1 for a mixed system with an open field). This indicator is much more accurate about the actual area where snails can disperse. Results showed that intensive farms with higher facilities scores have higher productivity, in agreement with previous experiments, in which all animals produced under laboratory conditions, become adults. In contrast, when fattening occurred in greenhouses, adults were 80% of the total production [39]. Furthermore, the small sample size limits the evaluation of the management and structural components that affect farm production.
The duration of the annual operation lasts between seven and nine months. According to other studies, under intensive rearing, marketable size takes four to five months [17]. Surely, the period of rearing could be expanded, which is not necessarily ideal. This increase (more than five months) has been proven to slow down snail growth and decelerate their adulthood [14]. The productivity per beneficial surface (0.58-6.15 kg × (m 2 ) −1 × year −1 ) was smaller than the one reported by Reference [13] (1.19-2.75 kg × (m 2 ) −1 × year −1 ) in mixed farming (reproduction in a controlled building and fattening in an outdoor park). Farmers use soil with growing plants, mostly as a substrate. As described in previous studies [1,40], snails fed only with green vegetables had slower growth and, at the end of the experiment, weighed eleven times lower than the ones fed with the compound ailment.
Snail farms in our research were dispersed in six different regions (Thrace, Central Macedonia, West Macedonia, Thessaly, Western Greece, and Attica-Islands) from low to high altitudes (759 m) and operated under highly variable temperature regimes. In those different localities and regions of Greece, there is a wide assortment of climatic types, portrayed by critical contrasts in the span and power of wet and dry periods [41]. The farms in Attica-Islands and Western Greece have the highest production because of the ideal climatic parameters. It should also be noted that all the farms in these regions were covered (three net-covered greenhouses and one elevated section). Because of low temperatures, West Macedonia and Thrace farms operate for a shorter period throughout the year. Seven out of eight farms in these regions are of the open field type, making them more vulnerable to local climatic conditions. Previous studies have shown that geographically distant natural snail populations can adopt distinctive life-history patterns due to adaptation to the local environmental conditions [23,24].
Compared to other agricultural systems that have long been established, snail farming in Greece is still evolving, and the present classification can aid farmers in deciding which method is more efficient both geographically and in terms of productivity. On the other hand, pork production systems in Greece have already evolved, from a family-type enterprise (herd size of 10-20 shows) to an industrialized, internal type with a remarkably large livestock number [30]. The same evolution was displayed in sheep, whereas, in the last decade and due to changing socioeconomic conditions, traditional systems have been replaced by others, characterized by a considerable capital investment and high ewe productivity [29]. In addition, dairy farmers changed their small-scale farms to an entrepreneurial livestock breeding activity. This action has facilitated the substantial improvement of the conditions under which dairy farms operate [28].

Conclusions
The assessment of modern farms' structural and management characteristics, including heliciculture, can contribute to sustainable food production. This is the first study that classifies snail farms in Greece and describes them in detail. Five farming systems (elevated sections, net-covered greenhouse, mixed system with net-covered greenhouse, open field, and mixed system with the open field) were identified. Results indicated that intensive farms exhibit high production. Geographical location affects production and influences the duration of operation, especially in open field farms. Snail farms in Northern Greece are forced to operate for a shorter period throughout the year.
Snail farming can be a potentially promising business, but this depends on a multitude of factors. We need more in-depth scientific knowledge and research on the breeding and growth of snails and the climatic and geographical aspects of the selected areas of farm settlement. The critical factors identified and the promotion of the product in national and international markets will guarantee business sustainability.