Noctilucent Crab Pots in the Yellow Sea, China: Field Evidence for Catch Efficiency Enhancement and Sustainable Crab Fishery Practices

Abstract

Artificial light has been shown to enhance the fishing efficiency of fishing gear by attracting marine organisms. This study introduces a novel approach by incorporating noctilucent materials into crab pots and evaluates their effects on catch performance. Based on the crab pots commonly used on the coast, four types of crab pots were tested: ordinary crab pots (Con-pot), ordinary crab pots equipped with noctilucent sticks (Exp-pot 1), crab pots equipped with noctilucent nets (Exp-pot 2), and crab pots equipped with both noctilucent nets and sticks (Exp-pot 3). The results showed that the noctilucent material exhibits 6 h persistent emission in darkness after just 10 min of solar charging. Exp-pot 3 could significantly enhance fishing efficiency, which increased by 63.84% compared to the Con-pot. The proportion of crabs in Exp-pot 3 was the highest (86.35%), and the individual weight of crabs in Exp-pot 3 was the heaviest (61.5 g), which was 38.30% heavier than that in the Con-pot. Notably, Exp-pots 2 and 3 demonstrated superior selectivity with higher W₅₀ values (53.01 g and 54.49 g), narrower SRs (33.04–72.98 g and 32.95–76.03 g), effectively balancing target catch retention with undersized crab release, indicated that noctilucent nets exhibited stronger weight selectivity for crabs compared to noctilucent sticks. These results demonstrate that functional materials have broad potential applications in fishing gear, which could enhance the catch efficiency and individual size of crab caught.

1. Introduction

Pot fishing is well known for its higher level of species selection and is widely practiced in coastal China. The target species of crab pots vary with the seasonal changes in the Yellow Sea of China. Whelk (Rapana venosa) and Asian paddle crab (Charybdis japonica) are the main target species in the autumn, and swimming crab (Portunus trituberculatus) becomes the dominant target species in the spring and summer. These species are widely distributed in the coastal waters of Japan, Korea, and the Yellow Sea and Bohai Sea of China, occurring from the intertidal zone to a large variety of habitats, including sandy, sandy–muddy, and rocky bottoms [1,2]. Crab pots are designed as enclosures that attract target animals to enter the gear through one or more entrances, often following the bait odor, while preventing or limiting their subsequent escape [3]. Since the 1980s, the increasing abundance of coastal crustacean resources has promoted the development of crab pot fisheries [4]. Nevertheless, the sustained growth in fishing intensity has led to declining crab stocks in some areas, along with a noticeable decrease in the average size of specimens caught. Under these circumstances, enhancing the catch efficiency of crab pots without escalating fishing pressure has become a pivotal issue for achieving sustainable fisheries.

Numerous studies have demonstrated that many commercially important marine species exhibit distinct attraction or avoidance responses to specific light wavelengths and intensities [5,6]. In practical fishery operations, artificial lighting technology has achieved remarkable success in various fishing methods, including falling net fisheries [7], stow net fisheries [8], squid jigging fisheries [9,10], and purse seine fisheries [11]. Particularly in crab pot fisheries, Nguyen et al. [12] confirmed that pots equipped with LEDs (light-emitting diodes) demonstrated comparable catch efficiency to traditional baited pots, and Bouwmeester and Ljungberg [13] reported that LED lights in shrimp pots increased catches of northern shrimp (Pandalus borealis) by 3.1 times. Meanwhile, Cerbule [14] discovered through field experiments that inserting artificial lights significantly increased the catch efficiency for snow crabs over the minimum landing size, i.e., 95 mm in carapace width. This increase was up to 76% when using green LEDs and 52–53% on average when using white LEDs. These findings provide important references for the application of lighting technology in pot fisheries.

Despite these advantages, LED systems face practical limitations, including reliance on external power sources, increased operational complexity, and susceptibility to corrosion in marine environments [15,16]. As an alternative, novel noctilucent materials exhibit significant advantages due to their unique energy-storing noctilucent properties. These materials can absorb and store sunlight energy, subsequently emitting light autonomously in dark environments without requiring additional power sources. Currently, noctilucent materials have been preliminarily applied in swordfish (Xiphias gladius) longline fisheries [17], but systematic research on their use in crab pots remains scarce. Crucially, the light emission intensity of these materials may vary depending on their placement, density, and combination, potentially affecting their attractiveness to target species.

Addressing this technological gap, this study innovatively incorporates noctilucent nets and sticks into crab pot design to investigate the effects of different assembly configurations on fishing performance. Four distinct pot types were tested: non-noctilucent pots, pots with noctilucent sticks only, pots with noctilucent nets only, and pots combining both noctilucent nets and sticks. We systematically evaluate the fishing efficiency of pots by analyzing total catch weight, species composition, and size selectivity based on individual weight distribution of captured specimens (with Charybdis japonica as the primary species). The research outcomes are expected to not only enhance crab pot fishing efficiency but also contribute significantly to the sustainable utilization of fishery resources.

2. Materials and Methods

2.1. The Area and Time of Sea Trials

The fishing operation was conducted from 27 September to 20 October 2022, within the Yellow Sea near Qingdao (35°36′ N, 120°00′ E) (Figure 1). The study area was a conventional fishing ground for Asian paddle crab (Charybdis japonica). The experimental zone featured mixed sand–mud substrates with an average water depth of 15 ± 5 m; the water temperature ranged from 22.6–24.8 °C at the surface to 18.3–20.5 °C at the bottom, salinity varied between 30.1 and 31.8 psu, dissolved oxygen levels were maintained at 6.2–7.8 mg/L, and pH values remained stable at 8.0–8.2 throughout the study period. The sampling sites were selected by local experienced fishers, and researchers conducted 24 scientific survey trials following commercial fishing protocols.

2.2. Noctilucent Sticks and Nets

The noctilucent stick used in the experiment was prepared by blending noctilucent powder with polymethyl methacrylate and conducting a melt extrusion process. The length and diameter of the noctilucent stick were 300 mm and 50 mm, respectively. The noctilucent monofilament was prepared by conducting a melt extrusion process and blending noctilucent powder with high-density polyethylene (HDPE). Fifteen noctilucent monofilaments were twisted into one strand to weave a net with a mesh size of 40 mm. Both the noctilucent sticks and nets were manufactured at the New Fishing Materials Laboratory of the East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences.

2.3. Experimental Crab Pots

Cylindrical crab pots constructed with HDPE nets and metal frames were used as the experimental crab pots. The crab pot frame had a bottom diameter of 580 mm and a height of 300 mm. The outer surface was covered with a polyethylene mesh with a size of 40 mm. The crab pot consisted of six sides, with three separate screen entrances with a large outer entrance and a small inner one (resembling a funnel) (Figure 2). The standard pots (Con-pot) were covered with HDPE nets (Figure 2a); experimental pots 1 (Exp-pot 1) were covered HDPE nets with a noctilucent stick inside the crab pots (Figure 2b); experimental pots 2 (Exp-pot 2) were covered by noctilucent HDPE nets (Figure 2c); and experimental pots 3 (Exp-pot 3) were covered by noctilucent HDPE nets and contained a noctilucent stick (Figure 2d).

2.4. Experimental Process

We tested the luminance attenuation and duration of noctilucent sticks and noctilucent nets under controlled conditions. At 13:00 on a clear autumn day (the light intensity was approximately 1.3 × 10⁵ lux), we exposed the noctilucent sticks and noctilucent nets to direct sunlight for 10 min to ensure complete photon absorption. Subsequently, we took the samples to a darkroom to eliminate external light interference. We secured a digital camera on a tripod to maintain consistent imaging geometry. We configured the camera with the following parameters: shutter speed of 1/60 s to avoid motion blur while capturing sufficient signal, ISO sensitivity of 800 to optimize signal-to-noise ratio, and aperture of f/2.8 to provide appropriate depth of field and light intake. We captured sequential images of the samples at predetermined time intervals under complete darkness. We maintained the ambient temperature at 25 ± 2 °C throughout the experiment to minimize thermal effects on phosphorescence.

For the crab pot fishing performance experiment, a total of 80 crab pots (20 pots per type) were deployed. Each pot type (20 pots) was assembled as a group by connecting pots to a main line with branch lines, with buoys and anchors (single anchor weight: 15 kg) configured at both ends (Figure 3). To minimize light interference between pot groups, a spacing of 150 m was maintained between each group. All pots were retrieved daily at 08:00, and after catch collection, they were redeployed to their original positions. The noctilucent sticks and pots absorbed sunlight during the approximately 30 min interval when placed on the deck during retrieval.

2.5. Weight-Based Selectivity Modeling

The size selectivity of the crab pot was modeled using a logistic regression curve [18] based on catch weight data (W, in grams). The probability of retention P(W) for an individual of weight (W) was expressed as follows:

$$P\left(W\right)={\displaystyle \frac{1}{1+e^{-b(W+\frac{a}{b})}}}$$

(1)

where P(W) is the probability of capture for an individual weighing W (g), a is the intercept parameter (dimensionless), and b is the slope parameter (units: g⁻¹).

Model parameters (a and b) were estimated via maximum likelihood estimation (MLE) using the GLM model (family = binomial) in R 4.3.0.

From the fitted logistic model, the following biological selection parameters were derived:

The 50% retention weight (W₅₀):

$$W_{50}=-{\displaystyle \frac{a}{b}}$$

(2)

which represents the weight at which individuals have a 50% probability of being retained.

The selection range (SR):

$$SR={\displaystyle \frac{2\mathrm{l}\mathrm{n}\left(3\right)}{b}}\approx {\displaystyle \frac{2.197}{b}}$$

(3)

which quantifies the steepness of the selectivity curve, defined as the weight interval between 25% and 75% retention probabilities.

The 25% and 75% retention weights (W₂₅, W₇₅):

$$W_{25}=W_{50}-{\displaystyle \frac{SR}{b}}$$

(4)

$$W_{75}=W_{50}+{\displaystyle \frac{SR}{b}}$$

(5)

These parameters were used to evaluate the gear’s ability to selectively retain target-sized individuals while allowing undersized specimens to escape.

3. Results

3.1. Glowing Effect of the Noctilucent Sticks and Nets

The glowing effect of the experimental noctilucent sticks and nets is illustrated in Figure 4. The noctilucent sticks and nets emit the strongest light intensity immediately after being placed in the darkroom then gradually weaken. After 6 h, the light intensity of the glow net diminishes to a level undetectable to the naked eye.

3.2. Catch Weight of Crab Pots

The catch weight of each type of crab pot is shown in Figure 5, demonstrating that crab pots equipped with noctilucent materials consistently outperformed Con-pots, with Exp-pot 1, 2, and 3 increasing the total catch weight by 16.19%, 44.35%, and 63.84%, respectively (all p < 0.01). While Exp-pot 2 achieved the highest single-day yield (Day 3: 1488.4 g, +281% compared to Con-pot), Exp-pot 3 demonstrated higher stability across all fishing times, showing 12.4% higher catches in 1st–13th fishing times and 26.7% in 14th–24th fishing times. This advantage was manifested in both reduced variability (CV = 38% vs. 62%) and complete avoidance of low-yield days (<450 g), indicating that using noctilucent nets and sticks could increase the weight of the catch.

The catch species included crabs (Charybdis japonica, Portunus trituberculatus, Paguridae, Ranina ranina, Portunus pelagicus), shrimp (Oratosquilla oratoria, Caridina cantonensis), fish (Hexagrammos otakii, Zoarces elongatus, Paralichthys olivaceus, Sebastodes fuscescens), shellfish (Busycon canaliculatu, Meretrix meretrix), and cephalopods (Octopus ocellatus) (

Table 1. Summary of catch data in the sea trials.

		Weight of Catch (g)				Number of Individuals
		Con-pot	Exp-pot 1	Exp-pot 2	Exp-pot 3	Con-pot	Exp-pot 1	Exp-pot 2	Exp-pot 3
Crab	Charybdis japonica	6660.5	5576.2	6763.5	8479.4	147	99	123	143
	Portunus trituberculatus	528.9	1544.5	1332.9	2198.3	11	29	17	25
	Paguridae	861.0	1817.9	3584.6	2814.0	8	11	11	12
	Ranina ranina	152.7	212.3	226.7	83.0	5	6	7	3
	Portunus pelagicus	0	0	109.7	0	0	0	6	0
Cephalopods	Octopus ocellatus	724.2	1246.2	1298.7	1289.4	14	20	21	18
Shrimp	Oratosquilla oratoria	315.0	136.7	170.1	159.7	11	8	9	11
	Caridina cantonensis	0	0	0	40.7	0	0	0	1
Shellfish	Busycon canaliculatu	249.5	511.8	151.1	71.1	3	4	3	2
	Meretrix meretrix	0	0	0	197.7	0	0	0	1
Fish	Hexagrammos otakii	35.2	0	0	14.5	1	0	0	1
	Zoarces elongatus	66.8	35.8	24.4	96.8	2	1	1	3
	Paralichthys olivaceus	19.2	0	0	0	1	0	0	0
	Sebastodes fuscescens	0	8.7	272.6	325.5	0	1	2	7

). In Figure 6a, the 13th fishing time results are missing due to an empty net (no catch). Crabs were the main species caught, while the weight of fish and shellfish caught was minimal. The average weight of crabs caught accounted for 83.60%, 81.62%, 84.04%, and 86.35% of the total catch in Con-pot and Exp-pot 1, 2, and 3, respectively (Figure 6). The analysis of fishing species proportions revealed that crabs remained the primary catch in crab pots, followed by cephalopods, which accounted for approximately 10% on average. In the Exp-pot 3, crabs constituted the highest proportion by weight, suggesting that using noctilucent nets and sticks in crab fishing could increase crab catches and reduce the proportion of non-target catches.

3.3. Individual Weight of Catch

The amount of fish and shellfish in the catch was too small to be statistically analyzed, but the individual weights of crab, shrimp, and cephalopod catches were statistically analyzed. Figure 7 shows a comparison of the effects of the individual weights of four types of crab pot on different catches (crabs, shrimp, and cephalopods). Figure 7a shows that the average weight of crabs in the Con-pot was 44.50 g, while those in Exp-pot 1, 2, and 3 were 55.61 g, 56.91 g, and 61.54 g, respectively. The weight of crabs in Exp-pot 3 was heaviest and 38.30% heavier than that in the Con-pot, indicating that the noctilucent materials effectively increased the weight of captured crabs. However, Figure 7b shows that the average shrimp weight in Con-pot and Exp-pot 1, 2, and 3 was 22.9 g, 12.1 g, 18.9 g, and 21.2 g, respectively. It was found that the pots containing noctilucent materials captured fewer shrimp, which may be due to the lack of significant benefits for shrimp from the noctilucent materials. Figure 7c shows that the average weight of cephalopods in the Con-pot was 60.1 g, while the weight of cephalopods in Exp-pot 1, 2, and 3 was 3.74%, 2.96%, and 19.26% higher, respectively. Like crabs, cephalopods have strong phototaxis, so Exp-pots show good fishing efficiency for cephalopods. In particular, for Exp-pot 3, it increased by 19.26% compared to the Con-pot. In a word, the results showed that the individual weight of crabs and cephalopods could be significantly increased by using assembled noctilucent sticks and nets in crab pots.

3.4. Weight Selectivity Analysis of Noctilucent Crab Pots for Charybdis japonica

The frequency distribution of weight classes of four crab pots for Charybdis japonica is shown in

Table 2. Frequency distribution of weight classes of four crab pots for Charybdis japonica.

Crab Pot	0–20 g	20–40 g	40–60 g	60–80 g	80–100 g	100–120 g	120–140 g	>140 g
Con-pot	32.65%	12.24%	24.49%	14.97%	8.16%	5.44%	1.36%	0.68%
Exp-pot 1	27.37%	12.63%	23.16%	17.89%	9.47%	3.16%	2.11%	4.21%
Exp-pot 2	18.70%	12.20%	24.39%	26.83%	11.38%	4.07%	0.00%	2.44%
Exp-pot 3	17.02%	15.60%	28.37%	15.60%	12.06%	4.96%	2.84%	3.55%

. It was found that the Con-pot captured a high proportion of Charybdis japonica individuals weighing less than 20 g, accounting for 32.65% of the total catch. This indicated that juvenile crabs represented one third of the catch. Additionally, in Exp-pot 1, individuals below 20 g still constituted a significant proportion at 27.37%. In contrast, for Exp-pots 2 and 3, the majority of captured crabs fell within the 40–80 g weight range, representing approximately half of the total catch. These results demonstrated that Exp-pots 2 and 3 captured fewer juvenile crabs. This performance better aligned with the requirements for sustainable fishery resource utilization.

To analyze the selectivity characteristics of crab pots for achieving the dual objectives of retaining target-sized individuals and releasing undersized specimens, logistic regression was used to analyze the weight selectivity of four crab pots for Charybdis japonica, evaluating performance through 50% selection weight (W₅₀) and selection range (SR); the individual weight selectivity curves are shown in Figure 8, and the selectivity parameters are shown in

Table 3. Selectivity parameters of four crab pots for Charybdis japonica based on logistic regression modeling.

Crab Pot	W50 (g)	SR (g)	b
Con-pot	42.71	18.83–66.59	0.046
Exp-pot 1	48.59	24.70–72.46	0.046
Exp-pot 2	53.01	33.04–72.98	0.055
Exp-pot 3	54.49	32.95–76.03	0.051

. W₅₀ determined the selectivity curve position, with higher values shifting the curve rightward and decreasing juvenile catches, crucial for crab resource conservation. In Figure 8, Exp-pots 1, 2, and 3 show significantly better performance than Con-pot, with W₅₀ values of 48.59 g, 53.01 g, and 54.49 g, respectively, compared to Con-pot’s 42.71 g, demonstrating that noctilucent materials improved the weight selectivity of the pots. SR affects the curve shape; wider ranges indicate weaker selectivity. In Table 3, the SR of Con-pot is 18.83–66.59 g, indicating a broad catch distribution, while Exp-pots have narrower SRs (24.70–72.46 g, 33.04–72.98 g, and 32.95–76.03 g), showing stronger selectivity. Moreover, the SRs of Exp-pots 2 and 3 are similar but narrower than that of Exp-pot 1, indicating that pots 2 and 3 exhibited stronger selectivity than pot 1. The parameter b serves as an indicator of selectivity strength, where higher values correspond to stronger selectivity. Both the Con-pot and Exp-pot 1 exhibited identical b values of 0.046, while Exp-pots 2 and 3 demonstrated increased values of 0.055 and 0.051, respectively. These results provide additional evidence that Exp-pots 2 and 3 possessed superior selectivity compared to Exp-pot 1.

4. Discussion

This study pioneers the field application of noctilucent materials in crab pot fisheries, demonstrating that strategic light configurations (sticks and nets) can significantly enhance catch efficiency. The 63.84% increase in catch yield with combined noctilucent gear (Exp-pot 3 vs. Con-pot, p < 0.01) not only confirms laboratory observations of phototaxis in Charybdis japonica [19] but also establishes a practical framework for optimizing light intensity in operational fishing gear, addressing a previously unexplored gap in coastal crab fisheries.

In current fishing light applications, LED lights have become the mainstream choice for surface fishing operations such as purse seine [20], stick-held lift nets [21], and squid jigging [22] due to their high brightness and adjustable characteristics. They are particularly effective in squid jigging by creating impressive light fields on the sea surface [22,23]. Chemical disposable submersible lightsticks perform well in deep-water operations like swordfish longline fishing because they require no power supply [24]. However, both technologies have significant limitations. When used underwater, LED lights face challenges with corrosion-proof sealing of power circuits, as seawater erosion easily causes short circuits, leading to high maintenance costs. Although chemical light sticks eliminate power dependency, the consumption of thousands of units per operation creates an ongoing financial burden. As Senko et al. [25] and Yu et al. [26] noted, technological ease-of-use and low cost were critical factors in fisher adoption. These technological constraints, in the form of power supply limitations for LED lights and the consumable material dilemma for chemical sticks, highlight the unique advantages of noctilucent sticks as an innovative material combining environmental durability and economic sustainability. By eliminating power reliance and avoiding recurring costs for chemical light devices, noctilucent sticks offer a more cost-effective solution for fishing light applications.

Although the phototactic mechanism of Charybdis japonica has not been fully elucidated, from observations of phototactic behavior in other crab species combined with catch data from this study, we can reasonably infer that Charybdis japonica likely exhibits positive phototaxis (a tendency to move toward light sources). It is well known that crustaceans (such as crabs and shrimp) possessed compound eyes composed of numerous ommatidia, with each ommatidium typically containing eight photoreceptor cells (seven proximal photoreceptors and one distal photoreceptor). This specialized visual system causes many nocturnal crab species to display characteristic light intensity preferences; they avoid bright light during daytime while engaging in feeding and migratory activities at dawn, dusk, or night. For instance, Luo et al. [27] found that the phototactic behavior of Portunus trituberculatus initially increased and then decreased with rising light intensity. Hugtes [28] proposed photoperiods as a key factor in maintaining circadian rhythms, while Vannini et al. [29] observed that light intensity triggered mass migrations in tree crabs (Sesarma leptosoma Hilgendorf), confirming light as a crucial environmental factor regulating crab behavior. Frank et al. [30] found that the visibility of phosphorescent-netting pots to snow crabs (Chionoecetes opilio) at 200 m depth primarily depends on the solar angle (time of day) and deployment duration, with secondary influences from water column quality and benthic turbidity, collectively explaining the differential effectiveness of various light sources in fishing outcomes. Based on the above research, we speculated that the fishing mechanism of the noctilucent crab pot targeting Charybdis japonica might operate in two stages: first, the light emitted by the pot attracts crabs from a distance, drawing them toward the structure. Subsequently, the internal noctilucent sticks guide nearby crabs into the pot, ultimately achieving successful capture (Figure 9). Combined with the stable catch data obtained in this experiment and the aforementioned research on crab phototaxis, we have reasonable grounds to believe that Charybdis japonica exhibits typical positive phototactic behavior. This characteristic makes it an ideal target species for the development of noctilucent crab pots.

Logistic regression analysis demonstrated that the Exp-pots exhibited significantly improved weight selectivity for Charybdis japonica. Compared to the Con-pot, the W₅₀ of Exp-pots showed a notable increase (Figure 8 and Table 3). Particularly, Exp-pots 2 and 3 displayed more concentrated SRs. These data confirmed a positive correlation between individual catch weight of Charybdis japonica and noctilucent materials, while also revealing that the noctilucent nets demonstrated higher attraction effectiveness for Charybdis japonica than the noctilucent sticks. Several key factors might explain these findings from different perspectives. Firstly, the visual system of the crab varied across ontogeny, leading to changes in spectral sensitivity and corresponding behavioral and physiological patterns [31,32]. These differences affected feeding strategies, spatial vision, navigation, and prey recognition [31,32,33]. Secondly, larger individuals possessed stronger swimming capabilities than smaller crabs, allowing them easier access to light sources. Additionally, Charybdis japonica is known to exhibit strong territorial consciousness and aggressive behavior [34]. In this context, larger individuals near noctilucent crab pots often created a deterrent effect, preventing smaller conspecifics from approaching the crab pot [35,36]. This territorial behavioral mechanism further suppressed the willingness of smaller crabs to approach the noctilucent sticks or enter the pots. Future studies could employ underwater videography to verify this hypothesis.

From the perspective of fishery management, this noctilucent fishing gear offered a promising tool for sustainable crab fisheries through its unique self-regulating mechanisms. The 6 h effective glowing duration (Figure 4) naturally aligned with the peak activity periods of crabs, which could help to enhance fishing efficiency. Moreover, the use of noctilucent nets demonstrated higher W₅₀ and more concentrated SR compared to noctilucent sticks alone, resulting in improved selectivity in crab pots. This enhanced selectivity effectively reduced bycatch of juvenile crabs, thereby strengthening resource sustainability. The high species specificity (83–86% target species in landings, Figure 6) minimized ecosystem impacts, a critical advantage over conventional gear that often requires strict mesh regulations to achieve similar outcomes. Additionally, the low bycatch ratio (<15% non-target species) suggested that this gear could ease regulatory burdens, particularly in seasonal closures or protected areas. By integrating light-based selection with natural crab behavior, this innovation represents a cost-effective alternative to traditional management, balancing ecological and economic objectives in crab fisheries.

When assessing the application prospects of this technology, researchers need to carefully evaluate its potential impacts on marine ecosystems. In pot fisheries, the general mechanism of capture is based on the attraction of the target animals by bait; the target animals then approach and enter the gear following the bait odor [37]. In this study, noctilucent crab pots maintain illumination for approximately six hours in underwater environments but cease emitting light when lost in dark benthic conditions, thereby reducing their ‘ghost fishing’ capability. Jin et al. [38] demonstrated through toxicological assessment that these noctilucent materials exhibit no adverse effects on fish cell viability at concentrations up to 0.1 mg/mL and negligible risks of biomagnification. This innovative energy-efficient design not only extends operational depth range but inherently minimizes ecological impacts through its self-terminating illumination system. Compared with conventional alternatives, this technology demonstrates significant improvements in bycatch reduction and carbon footprint mitigation, offering a sustainable solution that successfully reconciles fishing productivity with marine conservation objectives.

However, some limitations warrant consideration. The study did not examine potential habituation effects; crabs might alter their behavioral responses to artificial light sources with prolonged exposure. Future research should investigate whether repeated use could lead to diminished effectiveness or unintended population-level changes in crab behavior. These aspects are crucial in evaluating the long-term sustainability and ecological impacts of this technology.

5. Conclusions

In this study, noctilucent materials (sticks and nets) were applied to crab pots to evaluate their impact on crab-fishing efficiency. Field experiments revealed that noctilucent-equipped pots increased total catch biomass by 63.84% (from 9673.6 g to 15,849.2 g) while enhancing target species selectivity (with crab constituting 86.35% of the total catch). The average weight of crabs increased by 38.30% (from 44.5 g to 61.5 g), and noctilucent crab pots significantly enhanced the W₅₀ and SR for Charybdis japonica compared to Con-pot. Notably, Exp-pots 2 and 3 demonstrated superior selectivity with higher W₅₀ values (53.01 g and 54.49 g) and narrower SRs (33.04–72.98 g and 32.95–76.03 g), effectively balancing target catch retention with undersized crab release, which indicated that noctilucent nets exhibited stronger weight selectivity for crabs compared to noctilucent sticks, thereby providing an optimal solution for sustainable crab fishing.

These findings provide robust empirical evidence supporting the adoption of noctilucent materials in commercial crab pot fisheries. By simultaneously increasing yields and reducing juvenile crabs, this innovation offers a viable pathway toward sustainable fishing practices. However, it should be noted that due to the limitations of the 24-day trial period and the specific experimental conditions in the Yellow Sea of China, further validation is still required for long-term ecological effects and applicability in broader water areas. Future research should explore long-term ecological impacts and cost–benefit analyses to facilitate broader implementation.