The Conservation of the Endangered Monachus monachus: Could Maritime Workers Contribute to Its Study?

Simple Summary

Marine predators such as the Mediterranean monk seal (Monachus monachus) are attracted to offshore fish farms, and their interactions with these facilities have raised concerns about potential environmental impacts on surrounding marine ecosystems. This study explored the potential role of fish farm workers in monitoring marine biodiversity near aquaculture sites, comparing their possible involvement with that of other maritime workers. Interviews were conducted with these stakeholder groups to explore their perceptions of monk seal interactions with fish farms. Additionally, data were collected directly from fish farms to evaluate the accuracy of these perceptions. Fish farm workers are well-positioned to contribute due to their constant presence at sea and their proximity to key interaction zones. Moreover, nearly all maritime workers—including aquaculture workers—expressed no animosity toward monk seals during the interviews. With appropriate training, fish farm workers could become valuable participants in targeted citizen science initiatives and play a meaningful role in the ongoing monitoring of marine wildlife near aquaculture installations.

Abstract

The interactions between marine predators such as the Mediterranean monk seal (Monachus monachus) and fish farms have raised concerns regarding the potential environmental impacts of the industry on surrounding marine ecosystems. This study investigated the potential role of fish farm workers in monitoring marine biodiversity around aquaculture sites, comparing their potential involvement with that of other maritime workers. Interviews were conducted with maritime workers, including fish farm workers, in order to understand their perceptions of monk seal interactions with fish farms. The author also carried out direct data collection at fish farms to validate these perceptions. The results show a strong alignment between the workers’ perceptions and the data collected by the author on key parameters such as the presence, frequency, and seasonality of monk seals on fish farms. Furthermore, 75% of the 16 fish farm workers interviewed expressed no animosity toward monk seals. This underscores fish farm workers potential for involvement in monitoring initiatives and their understanding of monk seal interactions on fish farms. Given their constant presence at sea and proximity to key interaction zones, maritime workers are well-positioned to monitor environmental pressures and provide valuable data. With appropriate training, these workers could become valuable participants in targeted citizen science efforts, enhancing the public image of the aquaculture industry and advancing research on marine life in the vicinity of aquaculture installations.

1. Introduction

The Mediterranean monk seal (Monachus monachus) is classified as an endangered species by the International Union for the Conservation of Nature (IUCN), with an estimated global population of only 700–830 individuals [1,2]. Its distribution is fragmented, comprising two subpopulations in the northeastern Atlantic Ocean and one in the eastern Mediterranean Sea. In the northeastern Atlantic, approximately 350 individuals are found around the Cabo Blanco Peninsula (Western Sahara and Mauritania) [3], while the Madeira Archipelago (Portugal) hosts a much smaller group of approximately 27 individuals [1]. The population in the Mediterranean is estimated to range between 337 and 450 individuals [1].

Excessive hunting and fishing nearly drove the monk seals to extinction in Madeira, with only six individuals remaining on the Desertas Islands by 1988 [4]. Following the establishment of regional legal measures for the protection of the species and its habitat, the population is recovering and is found across both Madeira and the Desertas islands [4]. However, the proximity of human activities, such as construction, tourism, and (with 30% of fishermen reporting seal interactions in Hale’s study [5]), and the establishment of fish farms for gilthead seabream (Sparus aurata) in 1996 [4], continues to raise concerns about disturbances to this monk seal subpopulation. Furthermore, one cave used by seals on the north coast of Madeira lies just 11 km from Ilhapeixe, Lda., and nine other caves identified as suitable for use by seals are even closer to that fish farm (Figure 1) [4].

Aquaculture is widely recognized as a sustainable solution to address the increasing global demand for food, although it presents considerable challenges due to its interactions with ecosystems and wildlife [6]. Marine predators, such as seals, are frequently attracted to offshore fish farms, where they hunt near the cages. This often leads to net damage, stock losses, and fish escapes [7], raising concerns due to the unclear role of escapees in transmitting diseases to wild populations [8]. The financial impact on aquaculture has been documented in several countries, including Australia [9], the United States, Canada, Norway [10], Scotland [11], and Turkey [12]. For example, Turkey recorded 40 cage attacks across 11 farms over a seven-year and seven-month period [7], while Tasmania reported 106 fur seal (Arctocephalus spp.) attacks at 15 farms in just four months, prompting management measures to mitigate conflicts [11]. Similar concerns have also been reported about the interaction between monk seals and fisheries [5,13,14].

Fish farmers in Madeira have shown increasing awareness of the monk seal and its importance [15]. However, no formal strategy has yet been implemented to mitigate seal interactions in Madeira’s fish-farming areas. Nonetheless, preliminary efforts have been made to explore potential solutions, including trials involving the use of an acoustic deterrent device (ADD) [15]. In other countries, several measures have been evaluated, including ADDs, shooting, and anti-predator nets, with aquaculture managers presenting variable perceptions of the effectiveness of these solutions [9]. Physical barriers, such as perimeter fences and steel mesh nets, have proven to be among the most reliable methods to reduce predator access and mitigate potential conflicts with aquaculture sites [16], although this remains an ongoing topic.

The first reports of monk seal interactions with fish farms in Madeira, which involved net damage, were reported by fish farm workers in 1996 at the pilot fish farm in Baía de Abra, which is now operated by Ilhapeixe Lda. (Figure 1) [4]. The presence of monk seals has also been documented at two more recent farms operated by Aquailha Lda. and Marismar Lda. [17,18] (Figure 1). In 2015, a dead adult monk seal was discovered, with 52 gilthead sea bream of a similar size to one another in its stomach, at a location near Aquailha Lda. farm. As all fish farm companies on the island produce this species, it was assumed the seal had raided a fish farm or consumed escapees [4]. However, the cause of death was not possible to determine [4].

The Conservation Strategy for the Monk Seal in the Madeira Archipelago set the goal, to be met between 2020 and 2023, of defining and implementing a monitoring plan for aquaculture activities in Madeira to identify potential threats and develop measures to minimize their negative impact [4]. Although graduate students have carried out short-term studies of the marine fauna attracted to the fish cages with the logistical and technical support of fish farms and their workers [15,18], no long-term monitoring program is specifically focused on assessing the presence and behavior of monk seals in relation to Madeiran fish farms. A significant step was taken in April 2022 with the signing of a protocol between the government nature conservation institute and the fish farm companies [19]. This protocol aimed to address conflicts arising from the interaction between monk seals and aquaculture.

In Madeira, fish farms are situated in areas accessible only by boat, within aquaculture zones that are officially designated and restricted to vessels operated by the farms. Nevertheless, the fish farm cages are visible from both the sea and land. Moreover, at least two farms (Marismar Lda. and Ilhapeixe Lda.) are located near ports that are frequently used by tourist and leisure boats, making these areas common transit routes for non-aquaculture maritime traffic. One of the farms, Ilhapeixe Lda., is also located near a protected area, which facilitates access for wildlife rangers responsible for monitoring the monk seals’ presence and ensuring their protection.

This study explored the potential role of fish farm workers—among other maritime professionals—in monitoring marine biodiversity around aquaculture sites and contributing as citizen scientists. Thise study evaluated how these professionals, including aquaculture workers, currently perceive monk seals and their presence near fish farms. Interviews were conducted with workers from various maritime sectors to gather their perceptions toward monk seal interactions with aquaculture. Additionally, the author A.C.A conducted on-site observations at three fish farms in Madeira to provide a preliminary, independent assessment of the monk seals’ presence in these areas.

2. Materials and Methods

This study focused on the south coast of Madeira Island (from Calheta to Machico municipalities), where the three fish farms on the island are situated (Figure 1). Forty-six interviews were conducted among different marine workers between 17 February 2021 and 29 June 2021. The selection of participants was based on their potential to observe the species under study, the amount of time spent near fish farms, and their availability to participate in the interviews. The workers were classified into 4 categories: fish farm workers, dive club staff, whale-watching staff, and wildlife rangers. Interviews were conducted at the respondents’ workplaces in the municipalities of Calheta, Ribeira Brava, Funchal, Santa Cruz, and Machico (Figure 2).

The interviews were conducted by an interviewer who filled out a questionnaire based on the respondents’ verbal answers. The interviews were structured into four sections: aquaculture (4 questions), interactions between monk seals and fish farms (13 questions), the frequency of sightings by location (9 questions), and the demographic data of the workers (7 questions). Thise study did not investigate any relevant characteristics of monk seals, such as gender, age class, or size.

Responses to a question regarding the perceived impact of aquaculture on monk seals were classified as favorable (positive) if participants considered the interaction to be beneficial to the animal, or unfavorable (negative) if they perceived it as potentially harmful.

An additional two-question section was included to allow the interviewer to record participants’ reactions. Animosity was inferred from critical remarks expressed during the interview. Responses were rated on a four-point scale, ranging from “never” (no animosity) to “always” (consistent animosity), based on the frequency and tone of comments expressed throughout the interview.

The author A.C.A conducted on-site observations of monk seals at the three fish farms (Figure 1) over 9 months, from 30 September 2020 to 29 June 2021. On average, these observations occurred 3 times a month, resulting in a total of 27 opportunistic outings on boats belonging to aquaculture companies to observe monk seal interactions with fish farms. Whenever a seal was observed, images were taken and record sheets were filled in with the date and time of observation, the seal behavior (e.g., locomotion, predation, resting, play, or other activities), the developmental stage and sexual dimorphism (when possible), the period of the sighting, and the reaction of the fish farm’s employees (such as making noise, attempting to attract the seal with fish or bait, approaching the seal, touching it with an object, or trying to drive it away with a weapon).

The statistical analysis of the interviews was carried out in R (v4.3.2) [20]. Cluster analysis was used to understand the profile of individuals who perceive the interaction of the monk seal with fish farms as positive and those who perceive it as negative. To understand how factors such as workplace, education level, and years with the company influence workers’ perceptions, chi-square (χ²) tests were used to assess associations between categorical variables and perception type, while ANOVA (F) tests were applied to compare the means of the numerical variables across perception groups.

3. Results

3.1. Sociodemographic Profiles of Maritime Workers

In the sociodemographic analysis of the interviewees (

Table 1. Number of maritime workers interviewed by professional sector and workplace.

	Workplace
Professional Sector	Calheta	Machico	Ribeira Brava	Funchal	Santa Cruz
Fish farm workers	8	2	6	0	0
Wildlife rangers	0	4	0	2	0
Whale-watching staff	4	1	5	4	0
Scuba diving club staff	4	3	0	1	2

), the whale-watching and scuba-diving club staff had a relatively high level of education, with most having a bachelor’s degree (

Table 2. Sociodemographic characteristics of interviewed maritime workers (n = 46).

Professional Sector	Years in the Company (1)	Educational Level	Age (1) (Range)
Fish farm workers	5.6	Basic school	35.6 (22–53)
Wildlife rangers	20.8	High school	47 (43–50)
Whale-watching staff	7.1	Bachelor’s degree	34.4 (22–57)
Scuba diving club staff	18.9	Bachelor’s degree	46 (26–63)

⁽¹⁾ Average.

). The wildlife rangers and scuba-diving club staff had the longest careers within their respective organizations, with averages of 20.8 and 18.9 years, respectively (Table 2). They also represented the oldest age groups in this study, with average ages of 47 and 46 years, respectively.

3.2. Workers’ Perceptions of Presence and Observed Frequency of Occurrence of Monk Seals at Fish Farms

The perception of maritime workers regarding the frequency of seal occurrences at fish farms, as reflected in the responses to the interviews, was mostly that such interactions never happened (54.4%) or were “rare” (26.1%) (Figure 3).

Most respondents (78%) identified Ilhapeixe Lda. as the farm where seals were observed most frequently, which they attributed to the farm’s proximity to the Desertas Islands (21 km; Figure 1), a territory known to be home to a population of monk seals. However, 7% of respondents identified Aquailha Lda. as the farm with the highest frequency of seal sightings and 13% of respondents did not know at which aquaculture site the seals were seen most often (Figure 4).

3.3. Workers’ Perceptions of Monk Seal’s Seasonality of Occurrence in Madeira’s Fish Farms

Nearly half of the respondents (49%) were unsure about when seals most frequently appeared at fish farms. However, the most frequently mentioned peak months were February (15%), March (11%), and April (11%) (Figure 5).

3.4. Perception of Fish Farms’ Effects on Monk Seals and Worker Profiles Shaping These Views

The interview responses revealed that 62% of maritime workers believe that monk seal interactions with fish farms negatively impact the species’ conservation, either by harming the individual seal or jeopardizing the population’s long-term survival (

Table 3. Summary of main arguments provided during interviews to justify perceptions of interactions between monk seals and aquaculture (n = 46).

Main Arguments	Positive Perception	Negative Perception
Predictable feeding and increased prey availability	16
Consumption of unhealthy residues (sick fish, plastic, and antibiotic-treated fish)		5
Habituation to humans and population behavioral changes		15
Increased vulnerability to harm or accidents		6
Changes in habitat and its quality		7

).

In contrast, 38% of interviewees expressed positive perceptions, highlighting that easy access to food and a higher abundance of prey near fish farms may benefit monk seals. This group showed a wide range of ages (22 to 63 years) and educational backgrounds, from primary school to master’s degrees, with basic schooling being the most common qualification (6 respondents; n = 18). Their time working in the company varied from less than 1 year to 44 years, with a median of 9 years. The aquaculture sector was the most represented among those with positive views, accounting for 13 out of the 18 respondents (see Supplementary Table S1 for detailed data).

The group of respondents with negative perceptions displayed a wide age range, from 22 to 62 years. Their educational backgrounds varied from basic education to master’s degrees, with high school and bachelor’s degrees being the most common qualifications (10 respondents each; n = 28). The time spent working in the company ranged from less than 1 year to 28 years, with a median of 8.5 years (see Supplementary Table S2 for detailed data). Professionally, the whale-watching sector was the most represented among those holding negative views (13 respondents; n = 28).

The interview responses highlighted that those working in aquaculture areas (Calheta and Machico) tended to have more positive opinions (χ² = 18.4; p < 0.001), whereas maritime workers with higher educational levels (χ² = 11.9; p = 0.018) and more years at the company were more likely to express negative views (F = 8.27; p = 0.006) (

Table 4. Factors that most influenced the interviewed maritime workers’ positive or negative perception of monk seal interactions in aquaculture (summary of factor analysis resulting from chi-square tests and ANOVA tests).

Influencing Factor	Positive Perception	Negative Perception	Statistical Test Result
Workplace	High influence	Low influence	χ2 = 18.4; p < 0.001
Educational level	Low influence	High influence	χ2 = 11.9; p = 0.018
Years at company	Low influence	Moderate influence	F = 8.27; p = 0.006

).

3.5. Assessing Animosity Toward Monk Seals and Aquaculture Industry

Only 10.6% of respondents occasionally expressed animosity toward monk seals (n = 46), and 75% of the 16 aquaculture workers surveyed did not express any animosity toward the species. A total of 42.5% of respondents showed some level of animosity toward aquaculture (with conjoint values of “always” (12.7%), “frequently” (10.6%), and “sometimes” (19.1%)) (Figure 6). The main reasons given for this animosity were concerns about its perceived harm to monk seals and other species, or questioning its existence in Madeira. Among the respondents who expressed animosity towards monk seals, the concerns were usually related to whether the animals could financially compromise fish farming activities or human safety in the water.

3.6. Presence and Frequency of Occurrence of Monk Seals at Fish Farms Observed On-Site

During this study, a total of 13 monk seal sightings were recorded on-site, averaging fewer than 2 sightings per month (1.44 sightings).

The highest frequency of sightings occurred at the Ilhapeixe Lda. farm, representing 77% of all sightings (Figure 7). In contrast, monk seal sightings at Marismar Lda. farm occurred only 23% of the total records (Figure 7).

Sightings varied across months, with the highest occurrences of seals observed in February and March, each accounting for 31% of sightings (Figure 8).

4. Discussion

The relatively low educational level of the aquaculture workforce in Madeira was in line with that elsewhere in Europe, according to an FAO report [21]. However, Madeira’s workers are notably younger—ranging from 22 to 53 years—compared to the typical European age range of 40 to 64 years [21]. These younger workers could be particularly valuable for citizen science initiatives, which often rely on digital tools or online platforms [22,23] and benefit from participants’ ease with technology. In this research approach, citizens contribute to one or more stages of the scientific process—whether formulating research questions, collecting or analyzing data, or disseminating results—while adhering to criteria that ensure scientific rigor [24].

However, the career longevity (with an average of 5.6 years) of the Madeira fish farm workers was much less than the typical career experience in Norway, of over 15 years [25]. These differences are probably a reflection of the relatively recent establishment of Madeira’s aquaculture industry, with its first commercial farms appearing in 2004.

The whale-watching sector, by contrast, typically employs larger teams with higher academic qualifications [26,27]. In our sample, most whale-watching workers held bachelor’s degrees, and at least three had completed master’s degrees. Their average career longevity was 7.1 years, and the mean age was 34.4 years. These parallels reinforce our findings and suggest that, because these demographic profiles mirror those in other European coastal sectors, the insights derived from this study in Madeira could be applicable to similar regions, particularly with respect to workforce engagement.

Our results for the on-site fish farm observations, indicating only rare monk seal sightings and no attacks on the fish nets, matched the maritime workers’ interview responses stating that these sightings occurred “rarely.”

Ilhapeixe Lda. at Baia d’Abra was identified as the fish farm where most monk seal sightings occurred. Likewise, the interview results aligned with what was observed at the sites. According to Amaral [18], the proximity of resting and breeding sites may be one of the factors influencing the attraction of monk seals. In this context, the Ilhapeixe Lda. fish farm stands out for being located just 21 km from the Desertas Islands. Moreover, within an 11 km radius of the farm, nine caves have been identified as potential resting sites for monk seals, and one cave on the north coast of the island has been confirmed as a site used by these animals (Figure 1).

Between September 2022 and May 2023, after this study concluded, there were frequent sightings of monk seals and interactions reported at Marismar Lda., the westernmost farm [15]. The increase in the frequency of monk seal sightings at Marismar Lda. was associated with a decline in fish production at Ilhapeixe Lda., which may have reduced the number of fish attracted to the site, leading the seals to look for alternative farms that attract more fish around them [15]. In addition, the increasing number of reports of S. aurata escapes in certain fish farms may also be influencing the seals’ foraging behavior [8].

Almost half of the respondents stated that they were unaware of when seals most often visited fish farms. The accuracy of maritime workers’ sighting reports is higher when they are recorded or reported promptly to the responsible authorities. Delays in reporting created uncertainty, as many workers found it difficult to accurately recall the details of sightings at the time of the interview. When considering the respondents who were aware of when seals most frequently visited the fish farms, the perception of marine workers aligned with the data collected on-site regarding the period with the most frequent sightings, i.e., between February and March. The winter months were another period with more reported interactions between monk seals and Turkish fish farms [7]. The results of the on-site sightings collected by the author A.C.A suggest that Madeira’s maritime workers’ perception of seasonal sighting patterns was correct. It is essential to continue observation efforts and evaluate the influence of fish seasonality and fish escapes from cages to better understand the seasonal patterns of these interactions.

The respondents considered that interactions with fish farms were potentially harmful to monk seals. However, in a more recent study [15], no negative interactions between aquaculture and the Mediterranean monk seal were recorded. This suggests that the presence of seals near aquaculture sites can occur without causing direct harm to the animals or significant losses to the farms [15]. Their regular presence is likely linked to the availability of food [15], such as wild fish attracted to the area or escaped S. aurata. Still, regular foraging at these sites could, over time, affect the seals’ natural hunting abilities [15].

Beyond ecological impacts, the dynamics of these interactions also depend on fish farm workers’ practices as part of their job is to dive to ensure the maintenance of nets and fish farm cages, placing them in direct contact with the marine environment. Their reports indicate that when monk seals are present, diving fish farmer workers are more apprehensive, leading to longer times being required to carry out simple tasks to ensure safety procedures. Therefore, strategies should be developed collaboratively with scientists and relevant government authorities, as these dynamics may evolve over time depending on possible variations in seal behavior and human reactions.

Maritime workers, especially those in fish farms, tended to view aquaculture positively, likely due to their direct involvement and economic dependence on the activity. In contrast, whale-watching workers, who typically have higher educational levels and more years at their company, expressed more negative views, reflecting their concern for the environmental impacts. Repeating the interviews over time could clarify whether these views persist, considering the sectors’ high turnover rates.

The on-site data that were collected validated the perceptions of maritime workers across the four evaluated parameters (the presence/absence of seals in aquaculture, the total frequency of their presence, the frequency at each fish farm, and seasonality), suggesting these workers’ strong understanding of the interactions between monk seals and fish farms. This practical knowledge of maritime workers, combined with the systematization of information by scientists and academics, can form a solid basis for future studies, as demonstrated in other studies that evaluated the contribution of citizen science [28]. Furthermore, as already occurs in other countries, researchers’ use of opportunistic routes on aquaculture vessels also represents a valuable opportunity to further analyze these interactions [29,30].

Although most respondents showed no animosity toward monk seals, 42.56% expressed some degree of animosity toward aquaculture, reflecting growing concerns about the potential negative impacts of the sector. These impacts include threats to monk seals and other marine species, as well as wider questions about the presence of aquaculture in Madeira. This concern could instead be seen as an opportunity to involve workers in citizen science, promoting transparency and enhancing the sector’s public image. The appreciation of monk seals among maritime workers, including those in the aquaculture sector, could be a key factor in promoting future collaboration with researchers and authorities and encouraging the reporting of sightings [28].

As shown in more recent study, the fish farm workers recorded monk seal sightings, the time of day they were spotted, and other relevant details [15]. This demonstrates that, despite their relatively short careers and lower education levels, these workers can make meaningful contributions to scientific data collection when provided with appropriate training—particularly given their constant presence at sea [21].

It should be noted that citizen science, particularly in marine research, has proven highly effective in filling critical data gaps by providing information on species distribution and behavior. When combined with traditional scientific methods, it enables data collection across broader geographic areas and longer timeframes [8,22,28], reduces research costs [8,22,28], and lessens the need for specialist observers at every site [22]. Furthermore, it fosters public engagement through scientific communication and education [22], sharing knowledge in a dynamic way. Also, this approach can be especially valuable for documenting rare or sporadic events that might otherwise go unnoticed [23].

This type of involvement would not only support the conservation of the Mediterranean monk seal, but may also help to improve public perception of the aquaculture sector in Madeira. Perceptions of aquaculture vary based on factors such as transparency and environmental impact, emphasizing the industry’s need to address societal concerns [31]. This approach would generate mutual benefits for industry, academia, and government, reinforcing shared responsibility for protecting this endangered species and promoting sustainable aquaculture practices.

5. Conclusions

Continuous monitoring and long-term studies are essential for understanding the complex interactions between monk seals and fish farms, especially regarding the impacts of the seasonality of fish, escapees from aquaculture cages, and the behavioral variability of monk seals. This study suggests that local workers accurately perceived the interactions between monk seal and aquaculture in Madeira. Their practical knowledge, when aligned with scientific monitoring, reinforces the potential of involving aquaculture professionals in citizen science initiatives to support long-term wildlife monitoring and data collection.

The contrasting perceptions of aquaculture and whale-watching workers highlight the role of professional background in shaping views on environmental impact. Educating fish farm workers on responsible practices is crucial to minimize the risk to monk seals. These findings offer insights for Madeira as well as other coastal regions, showing how stakeholder engagement can enhance conservation efforts and promote more transparent and sustainable aquaculture practices.