Chasing Ghosts: Evidence-Based Management of Abandoned Fishing Gear in the Eastern Mediterranean

Abstract

The environmental problem of abandoned fishing gear (e.g., ghost nets) exists on a world scale. It impacts marine biodiversity for decades after the nets has become lost in the ocean. In Cyprus (eastern Mediterranean), ghost nets are found almost everywhere around the island, threatening marine life and human activities, such as scuba diving, fishing and navigation. To achieve meaningful outcomes for biodiversity conservation and the management of an offshore site that is particularly affected by ghost nets, the Jubilee Shoals, this issue is addressed in this study with an evidence-based approach. Pre-removal surveys were necessary to assess the nets and produce the environmental, ecological and structural data for the calculation of the Gear Removal Index (GRI). The results of a revised version of the index (GRI+) that includes species of conservation interest and invasive species were cross-checked in the field by divers with experience in marine ecology and similar removals. About 3 km of nets in total were successfully removed. The implementation of the GRI+ was an important proof-of-concept for environmental managers, aiding them to decide whether it would be necessary (or not) to perform removals and highlighting the index as a useful tool for the protection and management of Cyprus’ marine habitats.

1. Introduction

The environmental and socioeconomic problems of abandoned and lost fishing gear, particularly nets (hereafter ghost nets), are of global scale [1]. Between 500,000 and 1 million tonnes of fishing gear is abandoned, discarded or lost in the ocean every year [2]. Due to their designed purpose of catching fish, ghost nets pose a chronic impact on marine biodiversity which can last for decades after the gear has become lost in the sea, namely by continuing the trapping and killing of mobile species. Ghost-fished biodiversity (usually referred to as “ghost catch” [2]) includes not only commercial species but many others, including birds, marine mammals and turtles [3,4]. Ghost nets also alter the substrate on which they rest or in which they are ensnarled, significantly affecting shallow and deep benthic ecosystems, such as seagrass and coralligenous habitats [5,6,7,8,9].

Even though there is knowledge about the origin of this problem, as well as actions and alternatives to decrease the impacts, it is a problem that only seems to increase with time and is not only due to advances in the fishing industry and fishing rounds but also due to the availability of new, cheaper and more resistant materials with a prolonged utility life [4]. This type of plastic debris is infamous because of its wide-ranging impacts on ecosystem processes, habitats and organisms by facilitating the settlement and dispersal of invasive species [10] and incorporating plastics and toxic chemicals into food pathways [11,12,13]. The mortalities associated with ghost nets are linked to several environmental and ecological factors, such as the state of the nets, the topography of the seafloor, currents, the type of habitat, and species’ vulnerability and abundance, among others [4,9,14,15,16,17]. As a result, ghost nets, the most ubiquitous type of lost gear, are considered the deadliest form of marine plastic debris [6] and an important challenge to management and conservation efforts [18]. However, not all ghost nets will continue catching and killing indeterminately. The efficiency of the nets in catching mobile species changes with the physical state of the net itself and the increase in fouling that usually “stabilizes” the net by sinking and flattening it to the substrate. However, this process may require decades and there are many possible resting positions along the nets’ total length that could keep harming benthic or other communities.

Dramatic photos and videos of the ghost catch showing many degrees of damage and ensnarement [19] have contributed to raising awareness of the problem and implementing remedial actions (i.e., removals) that are not always properly regulated and do not always fall under a management action plan. For example, a common approach to the ghost nets is the business-as-usual “search and remove” approach, where the nets are located and soon after retrieved. However, the removals can seriously damage the same marine habitats that they seek to protect [9,17,20]. Despite this being a well-intentioned approach, no aspects except for logistics and depth are considered. Once the ghost nets are located, divers engage in their removal from the substrate, paying little to no attention to the living organisms colonizing the net. The longer the nets have been immersed, the higher the colonization by organisms [8]. However, the colonization degree may be species-specific and affected by the nets’ material and seasonal environmental fluctuations [21]. Careless removal activities of “aged” ghost nets usually cause more harm to the marine habitats than is acceptable, and this is mostly due to the destruction of colonizing species of EU importance (e.g., corals and sponges) and the damage to the attachment substrate (e.g., coralligenous communities).

In Cyprus, ghost nets are found almost everywhere around the island, threatening marine life and scuba diving activities and obstructing in-use fishing gear and navigation. The resilience of the marine habitats of Cyprus is already compromised by climate change and human activities. For example, marine heat waves have significantly impacted the marine biodiversity of the island by producing seawater warming which lasts for months, probably facilitating the spread of diseases and killing en masse sponges and other species [22,23]. Regrettably, ghost nets have become a permanent feature of the seascape and a pervasive source of deterioration of the already stressed-out marine communities of Cyprus. Hundredths of meters of massive, derelict nets of different ages and lengths, hanging and smothering benthic substrates, were confirmed during ecological surveys of coralligenous habitats and submarine caves in the Jubilee Shoals area, Cyprus [24]. In this study, our goal is to introduce an evidence-based approach assisting environmental managers in deciding whether they must (or not) remove particular ghost nets from the shoals and elsewhere.

The Gear Removal Index (GRI) is a decision support tool originally developed to guide the selective removal of ghost fishing gear based on ecological criteria [17]. First applied in studies across the central and western Mediterranean, the GRI enables field practitioners to evaluate the ecological value of ghost nets and determine whether removal is advisable, discouraged or neutral. The index incorporates field-based observations of net structure, fouling community composition and environmental context to assign priority scores. Its application is based on the principle that not all ghost nets are equal in ecological impact—some may serve as a substrate for sensitive benthic communities, while others may pose immediate hazards with little ecological value. The original GRI has been used in protected areas and biodiversity hotspots such as marine caves and coralligenous habitats, where unselective removal can cause significant ecological disturbance. The framework promotes a more strategic and evidence-based approach to marine debris mitigation, shifting the focus from purely visual or logistical criteria to ecological function and risk.

This study presents the first application and refinement of the Gear Removal Index (GRI) in the eastern Mediterranean, with a specific focus on the ecologically significant reef complex of the Jubilee Shoals, Cyprus. While the original GRI has been previously applied in other Mediterranean contexts, this study introduces a modified version (GRI+), incorporating region-specific ecological considerations, notably the presence of non-indigenous species (NIS) and the structural complexity of habitats such as submarine caves. The main aim of this study was to evaluate whether ghost nets should be removed based on the composition of fouling communities, net structure and ecological sensitivity of the surrounding habitat. This study did not test a formal statistical hypothesis, but it was guided by the expectation that nets supporting early successional, opportunistic species (e.g., green algae) would be prioritized for removal, while nets with “mature” biodiverse assemblages (e.g., Rhodophyta, Porifera) would be candidates for conservation. In doing so, this study demonstrates the operational value of the GRI+ as a decision-making tool for targeted net removal in biodiversity-sensitive marine environments.

2. Materials and Methods

2.1. Study Area

The Jubilee Shoals (34°36′34.1″ N, 32°47′24.3″ E), locally known as “Petra tis Avdhimou”, is a submerged, massive rocky outcrop located about 2.4 km off Avdhimou Bay on Cyprus’ southwest coast (Figure 1a). Most of the shoals’ area is within the Episkopi Special Area of Conservation (UK Sovereign Base Areas of Akrotiri) and the rest is under the jurisdiction of the Republic of Cyprus. This massive reef is home to a diverse ecosystem, featuring three priority habitats recognized by the EU Habitats Directive (Council Directive 92/43/EEC): Posidonia oceanica beds (habitat type 1120) mainly on the plateau but also around the outcrop, coralligenous assemblages along the shoals’ walls (habitat type 1170, ‘reefs’) and sciaphilic communities within submerged sea caves (habitat type 8330, ‘submerged or partially submerged sea caves’). The shoals are a popular spot for advanced diving and, unfortunately, also for fishing. Even though the place is a well-known cleaning, resting and mating station for sea turtles (Chelonia mydas and Caretta caretta), there are no systematic data about the sea turtles’ seasonal use of the shoals or about the frequency of entanglement and drowning of sea turtles. However, occasional observations from divers, boaters, competent authorities and our own records suggest that entanglement and drowning incidents occur on a monthly basis (during sea turtles’ peak mating season). The shoals’ summit is a plateau that lies at a depth of 17–21 m, while its base extends to approximately 45–55 m, depending on the surrounding seabed morphology. The shoals was selected for the present study due to its ecological importance (e.g., [24]), the confirmed presence of abundant derelict fishing gear, and its accessibility for the implementation of surveys and removals.

2.2. Removal Index

To assess whether a fishing net should be removed, the Gear Removal Index (GRI) from the methodological guide on abandoned fishing gear impacts [17] was applied as an aid for the final decision. A comprehensive and detailed description of the procedures and considerations implemented in the field to obtain the data needed to calculate the GRI is available in the original publication of the method [17]. Here, we present a succinct description of the method and the minor modifications made in this study to improve its applicability.

The GRI was designed with the aim of assisting in deciding whether to remove derelict fishing gear considering four essential parameters (impacts on the environment and the seascape, risks and technical issues) alongside their corresponding criteria and scores, which are given in Appendix A (

Table A1. The criteria of the GRI and GRI+ for assessing the “environmental impact”. Modified from Ruitton et al. [17] by adding percentages of cover to remarkable and invasive species (modified), and by removing the original scoring for invasive species (removed). All the other components are in the GRI+ (not modified).

Criteria	Assessments	Scores	Comments
Habitat	Posidonia meadow	2	Not modified
	Coralligenous	3
	Sublittoral reef formation	2
	Wreck	1
	Artificial reef	2
	Pebbles	1
	Sand	0
	Coastal detritic	1
	Mud	0
	Underwater canyon	2
Gear colonization	Stage 0	0	Not modified
	Stage 1	−1
	Stage 2	−3
	Stage 3	−5
Trapped mobile species	0 individual	0	Not modified
	1 to 2 individuals	2
	3 to 5 individuals	4
	>5 individuals	6
Species fixed torn off	0 individual	0	Not modified
	1 to 10 individuals	1
	>10 individuals	2
Damaged fixed species	0 individual	0	Not modified
	1 to 10 individuals	1
	>10 individuals	2
Remarkable species colonizing	0 individuals	0	Modified
	1–25% coverage	−2
	26–50% coverage	−4
	>50% coverage	−6
Invasive species colonizing	0 individuals	0	Modified
	1–25% coverage	2
	26–50% coverage	4
	>50% coverage	6
Presence of remarkable species colonizing the gear	Yes	−1	Removed
	No	0
Remarkable species in the vicinity of the gear	Yes	1	Not modified
	No	0
Engagement of the impact	0 m2 to 5 m2	1	Not modified
	5 m2 to 20 m2	3
	>20 m2	5
Fishing capacity	Nil	0	Not modified
	Small	2
	Large	4
Substrate abrasion	Nil	0	Not modified
	Small	1
	Large	2
Obstructed crevices	0 crevice	0	Not modified
	1 to 10 crevices	1
	>10 crevices	2
Habitat creation	Yes	−1	Not modified
	No	1
Total		−7 to 28

,

Table A2. The criteria of the GRI and GRI+ for assessing the “seascape impact”. From Ruitton et al. [17].

Criteria	Assessment	Scores
Seascape modification	No	0
	Yes	1
	Neutral	0
Adjective qualifying the gear	Negative	1
	Positive	−1
Topography	No changes	0
	Decrease of topography	2
	Increased of topography	−2
Total		−3 to 4

,

Table A3. The evaluation criteria of the GRI and GRI+ for the “site usages”. From Ruitton et al. [17].

Criteria	Assessment	Scores
Swimming	No	0
	Yes	3
Scuba diving/snorkelling/ spearfishing	No	0
	Yes	3
Sailing/mooring	No	0
	Yes	1
Fishing	No	0
	Yes	1
Total		0 to 8

and

Table A4. The criteria of the GRI and GRI+ for evaluating the “technical difficulties”. From Ruitton et al. [17].

Criteria	Assessment	Scores
Depth	0–15 m	0
	15–30 m	1
	30–50 m	2
	>50 m	3
Engagement	Low (0–10%)	0
	Medium (10–50%)	1
	Important (>50%)	2
Total		0 to 5

). The expression for the calculation of the GRI for each ghost net is

GRI = Ie + Is + Ru − Dt,

where Ie denotes environmental impacts (fishing capacity, for example, active entanglement, ghost fishing; ranking from −7 to 28; Table A1), Is corresponds to seascape impacts (e.g., changes in the topography; ranking from −3 to 4; Table A2), Ru is risks to users (e.g., divers; ranking from 0 to 8; Table A3) and Dt is technical difficulties (e.g., depth; ranking from 0 to 5; Table A4). The Dt component is subtracted from the total score, based on the rationale that higher technical challenges—such as greater depth, substrate adhesion or equipment limitations—reduce the feasibility of safe removal. This scoring logic ensures that removal priority is not based solely on ecological urgency but also considers diver safety and practical constraints. The higher the GRI, the more advisable it is to remove that particular ghost net (removal priority 1) (

Table 1. Decision making levels according to GRI values. From Ruitton et al. [17].

GRI Value	Removal of the Gear	Priority
30 < GRI < 40	absolutely advised	1
20 < GRI < 30	very highly advised	2
10 < GRI < 20	highly advised	3
0 < GRI < 10	advised	4
−15 < GRI < 0	not recommended	5

).

The original GRI was developed and implemented in the western Mediterranean Sea, an area with ecological characteristics markedly different from those of the eastern Mediterranean. While the western basin tends to be quite productive, the eastern Mediterranean is characterized by oligotrophic conditions and a high prevalence of non-indigenous species [25,26] which often dominate the biofouling communities. As a result, the direct application of the original GRI to the eastern basin required adaptation to ensure that the outcomes remained ecologically meaningful and context-sensitive. To address this, two categories were modified and one existing category was removed because it is now incorporated in a modified version, specifically within the “Environmental Impacts” component of the GRI. This modification was necessary to recalibrate the scoring mechanism so that it accurately reflects the ecological realities of the eastern Mediterranean. The first new category, “Remarkable Species Colonising” (Table A1), was designed to capture the potential ecological value of ghost nets as substrates for rare or ecologically significant native species (e.g., [27,28]). This category is scored from 6 to 0, with lower scores indicating a higher presence of such species—under the assumption that their presence may suggest a net’s positive contribution to habitat complexity or biodiversity, thus reducing the urgency for removal. Conversely, the second added category, “Invasive Species Colonising” (Table A1), addresses the presence of harmful non-indigenous species [29]. It is scored from 0 to 6, with higher scores reflecting greater colonization by invasive taxa and therefore indicating a higher ecological risk. With the inclusion of this category in the original GRI, the presence of invasive species is accounted for and places the modified GRI more in line with the eastern Basin ecological reality. To maintain balance within the overall scoring system, the previous category “Presence of Remarkable Species Colonising the Gear”, which had a limited scoring range (−1 to 0), was removed (Table A1). These modifications aim to better reflect the ecological dynamics of the eastern Mediterranean by emphasizing both the potential positive role of ghost nets in supporting marine biodiversity and the risks they pose when colonized by invasive species. The resulting selection of nets to be removed was cross-checked in situ by divers (see below).

2.3. Field Data Collection

Two sampling surveys were conducted in June (10 days) and October/November (9 days) 2024. To maximize efficiency at depths of 30–55 m, divers used rebreathers, thus extending their bottom time, and underwater scooters to cover more ground. During the first survey, ghost nets were located and their resting position on the coralligenous habitats of the shoals, depth, and surface area were recorded. Each net was tagged (water-proof playing cards) with a unique code for future reference, and photo-quadrats of the encrusting communities on the nets were taken using a 25 cm × 25 cm PVC frame (Figure A1) and a SONY α7C II full-frame camera (Sony Corporation, Tokyo, Japan) with two Bigblue Dive Lights VL11000P (Bigblue Dive Lights, Hong Kong, China). The quadrat size (625 cm²) is within the range of the commonly used frames in benthic studies—from 247 cm² to 2500 cm² (e.g., [30,31])—and was specifically selected to ensure the inclusion of encrusted areas when surveying in spatially constrained settings while maintaining the high-resolution imagery necessary for identifying small taxa. The number of photo-quadrats per net was five, eight and ten for nets up to 5 m², 20 m² and 50 m², respectively. In total, 180 photographs were taken. The second survey focused on removing pre-selected ghost nets after using the adjusted GRI (GRI+), including the cover percentages of attached organisms.

2.4. Data Processing

After selecting for images that met strict quality control criteria (e.g., clarity, correct framing, no distortion, absence of motion blur), only 145 photo-quadrats were analysed from the pool of 180 photographs. The photo-quadrat images were analysed using PhotoQuad v1.4 [32] to calculate percentages of cover of the substrate, each with 100 uniformly distributed points. Organisms (>1 mm) were identified to the lowest possible taxonomic level, and otherwise into morphospecies. For the purposes of this study, we pooled the percentages of cover into seven major categories (Ascidiacea, Bryozoa, Chlorophyta, Cnidaria, Porifera, Rhodophyta, non-living substrate) following the protocol used in other studies to evaluate substrate cover in the Levantine Sea [30,33,34]. Pooling into the major categories enables a general overview of the fouling community, which aligns with the aim of identifying broad patterns in the habitat’s (i.e., ghost nets) associated biodiversity. Nonparametric statistical analysis of variances (Kruskal–Wallis’ test, α = 0.05) for the comparison of categories was conducted using PAST software v.5.2.1 [35]. Dunn’s post hoc test was run to determine which categories were significantly different from the others. The presence and percentage of cover of rare or less abundant taxa were accounted for in the scoring and calculations for the GRI+. The index specifically incorporates the presence and identity of rare and/or sensitive taxa as part of its evaluation criteria, providing a distinct framework that addresses conservation concerns beyond the dominant cover categories.

3. Results

3.1. Ghost Nets in the Shoals

Twenty-five massive ghost nets were located in diverse positions and degrees of ensnarement to the rocky substrate and to the coralligenous structures, for example attached or hanging from the vertical flanks of the shoals and extending for dozens of metres down to the bottom and over boulders and coralligenous concretions (Figure 1b–d). Of particular interest for the removals were the nets found at the eastern entrance of a cave system, one of the main attractions of the Jubilee Shoals. These nets were a hazard to divers but also smothered coralligenous communities on the cave’s entrance walls and exterior ledges. These “curtain-like” nets partially or completely obstructed the openings, with potential implications for light availability, water circulation and mobile species access. Approximately 95% of the nets (from 2 m² to 30 m²) were identified as trammel nets, fabricated primarily from synthetic fibres such as polyethylene or nylon; these nets are likely associated with coastal fisheries. A few larger (from 72 m² to 150 m²), coarser trawl nets (synthetic fibres) were also documented, typically associated with industrial fishing operations. The remaining 5% consisted of gillnets (from 18 m² to 50 m²) made from monofilament nylon. Details of each net’s characteristics are presented in Appendix B (

Table A5. A summary of the main characteristics of the 25 ghost nets recorded at the Jubilee Shoals: net identifier (Net_ID, same as the playing cards used for tagging), depth (m), estimated length and height, calculated area, material of fabrication and attachment to substrate.

Net ID	Depth (m)	Length (m)	Width (m)	Area (m2)	Material	Attachment
6_♠	55	8	2	16	Synthetic fibres	Partially
J_♦	50	12	2	24	Synthetic fibres	Partially
10_♦	50	6	1.5	9	Synthetic fibres	Yes
8_♦	50	6	1	6	Synthetic fibres	Partially
7_♦	50	4	1	4	Synthetic fibres	Yes
6_♦	50	10	2	20	Synthetic fibres	Partially
3_♦	50	1.5	9	13.5	Synthetic fibres	Partially
4_♠	50	3	2	6	Synthetic fibres	Yes
5_♠_	50	8	0.5	4	Synthetic fibres	Yes
2_♦	45	25	2	50	Monofilament nylon	Partially
A_♦	45	15	10	150	Synthetic fibres	Partially
5_♣	45	2	4	8	Synthetic fibres	Yes
J_♣	44	10	0.5	5	Synthetic fibres	Yes
Q_♣	42	8	3	24	Synthetic fibres	Partially
10_♣	42	15	2	30	Synthetic fibres	Partially
6_♣	41	5	1	5	Synthetic fibres	Partially
5_♦	40	10	0.5	5	Synthetic fibres	Yes
4_♦	40	2	1	2	Synthetic fibres	Partially
K_♣	40	3	2	6	Synthetic fibres	Partially
9_♣	36	12	6	72	Synthetic fibres	Partially
7_♣	36	4	2	8	Synthetic fibres	Yes
K_♦	35	6	3	18	Monofilament nylon	Partially
Q_♦	35	2	15	30	Monofilament nylon	Partially
9_♦	30	4	2	8	Synthetic fibres	Partially

).

3.2. Benthic Community Composition

A total of 31 taxa (including morphospecies) and 4 non-living substrates (NLSs) were found on the surveyed ghost nets (Appendix B 

Table A6. A summary of the mean percent and standard deviation (Std Dev) cover for each species from 25 ghost nets and the species’ status (e.g., [17]). Not assessed for conservation status (NACS).

Taxon	Categories	Mean	Std Dev	Status
Bonnemaisonia sp.	Chlorophyta	0.14	0.39	Invasive
Caulerpa cylindracea Sonder, 1845	Chlorophyta	0.66	3.23	Invasive
Codium bursa (Olivi) C.Agardh, 1817	Chlorophyta	0.07	0.2	Remarkable
Dictyopteris polypodioides (A.P. De Candolle) J.V.Lamouroux, 1809	Chlorophyta	0.56	1.54	NACS
Dudresnaya verticillata (Withering) Le Jolis, 1863	Chlorophyta	1.28	2.34	NACS
Padina pavonica (Linnaeus) Thivy, 1960	Chlorophyta	0.77	1.91	NACS
Morphospecies 1	Chlorophyta	1.81	4.49	NACS
Morphospecies 2	Chlorophyta	3.61	11.58	NACS
Palmophyllum crassum (Naccari) Rabenhorst, 1868	Chlorophyta	0.45	1.04	NACS
Pseudochlorodesmis furcellata (Zanardini) Børgesen, 1925	Chlorophyta	0.64	2.66	NACS
Morphospecies 3	Chlorophyta	53.93	21.79	NACS
Lithophyllum sp.	Rhodophyta	13.78	11.97	Remarkable
Peyssonnelia rubra (Greville) J.Agardh, 1851	Rhodophyta	4.13	9.32	Remarkable
Peyssonnelia squamaria (S.G.Gmelin) Decaisne ex J.Agardh, 1842	Rhodophyta	2.2	5.56	Remarkable
Agelas oroides (Schmidt, 1864)	Porifera	1.49	2.93	Remarkable
Dysidea sp.	Porifera	0.76	3.74	Remarkable
Geodia sp.	Porifera	0.43	1.79	Remarkable
Ircinia oros (Schmidt, 1864)	Porifera	1.45	2.55	Remarkable
Ircinia sp.	Porifera	0.01	0.03	Remarkable
Oscarella sp.	Porifera	0.77	1.65	Remarkable
Petrosia (Petrosia) ficiformis (Poiret, 1789)	Porifera	0.21	1.02	Remarkable
Spirastrella cunctatrix Schmidt, 1868	Porifera	1.13	2.05	Remarkable
Morphospecies 4	Porifera	0.29	0.98	Remarkable
Morphospecies 5	Porifera	0.19	0.64	Remarkable
Hydrozoans 1	Cnidaria	0.07	0.25	NACS
Beania magellanica (Busk, 1852)	Bryozoa	0.48	1.92	Remarkable
Hippelozoon sp.	Bryozoa	0.07	0.34	Remarkable
Schizomavella sp.	Bryozoa	0.41	0.78	Remarkable
Smittina cervicornis (Pallas, 1766)	Bryozoa	0.51	1.59	Remarkable
Halocynthia papillosa (Linnaeus, 1767)	Ascidiacea	0.03	0.1	Remarkable
Dead Posidonia oceanica	NLS	0.9	2.57	N/A
Net	NLS	2.89	11.56	N/A
Rocks	NLS	0.32	0.84	N/A
Sand	NLS	3.55	5.41	N/A

). The colonizing organisms represented a variety of six phyla (categories) (Appendix B 

Table A7. The percentage cover of major benthic groups recorded on each surveyed ghost net, along with the calculated values for the ghost Gear Risk Index (GRI) and its extended version (GRI+). Benthic cover based on the analysis of photo-quadrats for each net. NLS = non-living substrate. GRI and GRI+ values are derived from cover composition, the presence of sensitive taxa and substrate interaction parameters. Net identifier (Net_ID, same as the playing cards used for tagging).

Net ID	Ascidiacea	Bryozoa	Chlorophyta	Cnidaria	Porifera	Rhodophyta	NLS	GRI	GRI+
6_♠	0	1.38	68.88	0	10.5	17	2.25	10	13
J_♦	0	0	81.83	0	8.17	5.5	4.5	13	17
10_♦	0	0	78	0	1	4.33	16.67	11	19
8_♦	0	2.36	60.86	0	2.07	31.14	3.57	9	12
7_♦	0	0	37.67	0	20.33	17.67	24.33	4	8
6_♦	0	1.75	58.13	0	2.38	37.38	0.38	12	17
3_♦	0	4.8	32.1	0	12.4	47.3	3.4	4	7
4_♠	0	4.4	44.6	0	12.2	38.8	0	−2	1
5_♠	0	1.67	81.33	0	1.33	3.67	12	7	17
2_♦	0	0	72.1	0	1.4	9.2	17.3	10	14
A_♦	0.2	1.1	63.4	0	10.1	25.2	0	11	14
5_♣	0	0	13	0	5.2	25	56.8	8	12
J_♣	0	11	45.67	0	7.33	30	6	3	7
Q_♣	0	0	49.75	0	12.38	37.88	0	11	13
10_♣	0.44	3.44	79.78	0	1.11	11.78	3.44	12	14
6_♣	0	0	33.33	0	0	63.33	3.33	−2	1
5_♦	0	1.67	68	1	13.67	6.33	9.33	11	15
4_♦	0	0	96.67	0	3.33	0	0	8	12
K_♣	0	0	41.25	0	5.75	53	0	−1	2
9_♣	0	0.5	89.5	0	8.13	1.88	0	13	23
7_♣	0	0	80.4	0	0.8	13.4	5.4	0	10
K_♦	0	0	77.43	0	6.14	6.14	10.29	−2	3
Q_♦	0	0.14	86.57	0	1	10.71	1.57	8	16
9_♦	0	0	96.2	0	0.2	0	3.6	11	21

), though macroalgae were by far the most dominant (H = 107.6, df = 5, p < 0.001; Figure 2a). Among the three categories with the highest percentage of cover, Chlorophyta accounted for the largest at about 64 ± 22.5% (mean ± standard deviation), followed by Rhodophyta at 20.7 ± 18.1% and Porifera at 6.1 ± 5.5% (post hoc p < 0.0001). Other categories, such as Bryozoa (1.4 ± 2.5%), Cnidaria (0.04 ± 0.2%) and Ascidiacea (0.03 ± 0.1%), were present in similarly low mean cover (post hoc p > 0.05). Non-living substrates represented 7.7% of the total.

3.3. Application of the Removal Index to Ghost Nets

The GRI was initially applied uniformly to all ghost nets, without accounting for ecological complexity or taxonomic specificity. The first analysis placed five nets in Priority 5 (removal not recommended), nine in Priority 4 and ten in Priority 3; none of the nets fell under Priorities 2 or 1 (very highly to absolutely advised to remove) (

Table 2. Number of ghost nets and removal priority according to original GRI and adjusted GRI+.

Priority	Removal	GRI	GRI+
1	absolutely advised	0	0
2	very highly advised	0	2
3	highly advised	10	14
4	advised	9	8
5	not recommended	5	0

). However, when the assessment was refined—through the application of revised thresholds and more ecologically sensitive criteria—the classification outcomes changed substantially. The revised evaluation (RGI+) found no nets in Priority 5, eight in Priority 4, fourteen in Priority 3, two in Priority 2, and none in Priority 1 (Table 2). This shift illustrates how important methodological adjustments can be in capturing differences in the ecological function or succession across ghost nets.

An observable pattern emerged when comparing biodiversity composition to the removal priority levels. The two nets placed in Priority 2 were largely dominated by Chlorophyta, which made up an average of 92.8% of the biological cover. In contrast, the nets categorized as Priority 3 showed an average of 68.5%, and those in Priority 4 had an even lower average of 49.1%. Meanwhile, Rhodophyta followed the opposite trend. Their presence increased from just 0.9% in Priority 2 nets to 16.1% in Priority 3 and reached 33.7% in Priority 4. The NLSs also varied across priority levels: 1.8% in Priority 2, 9.1% in Priority 3, and 6.6% in Priority 4.

3.4. Removals

The second survey focused on removing pre-selected ghost nets using the revised GRI+ that includes the cover percentages of attached organisms. All pre-selected nets went through another inspection by the divers with an ecological background and experienced in removals of ghost nets to cross-check the results of the GRI+. In general, there was excellent agreement between the index and the expert opinion, i.e., nets deemed to be removed were also selected by the divers. Following protocol, divers used knives to carefully cut nets or sections of the nets from the coralligenous structures on the walls, minimizing damage to the habitats. Lift bags, placed at 5-to-10-m intervals, were used to bring the nets to the surface. The process required precise coordination between divers and the surface team onboard the vessels to ensure both safety and efficiency. About 3 km of the nets deemed most harmful for the environment, and which also posed a safety risk to diving activities, were removed.

4. Discussion

It is only relatively recently (mid 1980 s) that the ghost nets issue has gained international recognition [4], and this might account for the current lack of a systematic management approach to deal with the problem and the many different responses from environmental managers and the general public. Ghost nets, particularly nets that have been recently lost, are deadly effective for the sole reason that they were designed to “capture and kill” and they will continue doing that in most cases [9,33]. As a result, removal of those nets is the most common approach. However, removal of nets without taking into account ecological factors and careful evaluation is certainly not the best approach [9,17,20]. The importance of implementing an evidence-based protocol to help managers decide whether ghost nets should be removed or not was demonstrated in this study, using the important marine habitats of the Jubilee Shoals as an example.

Analysis of the communities fouling the nets was necessary, and the percentages of cover show a strong prevalence of opportunistic algal colonization, particularly by green algae. The significant presence of Rhodophyta (calcareous algae) on some nets indicates a more established fouling community of species of conservation importance [8,9,34], which was reflected in the GRI+ values and removal priorities. While green algae dominance was evident in our results, this pattern deviates from regional baselines. In similar coralligenous habitats in Cyprus, and in the same Jubilee Shoals area (especially at comparable depths), Rhodophyta, in particular crustose coralline algae, are typically the dominant group [24]. Thus, the observed macroalgal prevalence should not be interpreted as a typical condition. Overall, the trends show that ghost nets categorized with higher GRI+ priorities (Priority 5 = removal is not recommended) support more taxonomically diverse and ecologically important communities (i.e., foundational species of coralligenous habitats), while those with lower priorities (Priority 1 = removals absolutely advised) are primarily colonized by early successional, fast-growing algae. Removal of those nets with significantly important communities will affect the species, causing further ecological damage. As a result, the management approach to the ghost nets issue should be evidence-based, not only driven by passionate or aesthetical reasons; it needs pre-surveys of evaluation, analysis and decision making based on evidence, i.e., targeted solutions [1,9]. As such, the direct application of the original GRI to the eastern basin required adaptation to ensure that the outcomes remained ecologically meaningful and context-sensitive. Since this study took place in the eastern Mediterranean, where non-native species are more prevalent than anywhere else in the world’s seas [26], the GRI was adjusted accordingly. As a result, an additional evaluation factor for non-native species presence was included in the revised index (GRI+).

Given the wide range of negative ecological impacts of ghost nets, the removal of the nets most harmful to biodiversity and those that posed a high safety risk to divers should benefit the general ecosystem of the Jubilee Shoals as well as the non-extractive human activities in the area (e.g., scuba and free diving) [24]. The removals were performed following a consistent protocol that was demonstrated to the competent authorities and decision makers responsible for the conservation and protection of the shoals. We explicitly made the case that the evidence-based approach is only an aid for decision-making, and that it should be complemented with expert opinion (e.g., divers and marine ecologists). It represents the first step in the implementation of the method in other areas of the Levantine Sea with similar problems [36,37], and in the achievement of managing the pervasive issue of ghost nets. However, there are other important methodologies which are recommended for the assessment of the impacts of removals and the subsequent evolution of the benthic communities [9,38].

Lastly, it is of utmost importance to emphasize that for the appropriate management of ghost nets, tackling the root of the problem is better than concentrating only on actions to mitigate the impacts [38,39]. Fishing activities are the source of the ghost nets; therefore, close collaboration with this sector is required if we want to reduce the amount and frequency of abandoned and lost gear [4,40,41,42,43,44,45,46]. Removals will always be essential but must be implemented under a systematic approach and in parallel with preventative measures, such as educational activities, the marking of fishing gear, constant hauling of static gear, early reporting of gear loss and enforcement of regulations for fishing [47].