Toward a Sustainable Surimi Industry: Comprehensive Review and Future Research Directions of Demersal Fish Stock Assessment Techniques

Abstract

The surimi industry faces challenges due to the overexploitation of demersal fishes, requiring precise fish stock assessments and the exploration of alternative raw materials. Research in these areas is crucial for fish sustainability. Thus, the current study aims to identify the existing knowledge covering the use of the length-based spawning potential ratio (LB-SPR) as a fish stock assessment method and to fill the gap in the research by consolidating relevant literature through a PRISMA SLR, using qualitative and quantitative data. The findings indicate that the LB-SPR method, while effective, needs to be utilized more in the surimi industry. This review highlights the need for precise stock assessments, historical data collection, and advanced sampling technologies, which are crucial for accurate data collection to conduct LB-SPR studies to assess fish stocks. Our study finds that significant research gaps include the need for more empirical studies on reproductive biology and the crucial role of interdisciplinary research in enhancing the long-term viability of fish stocks and the health of marine ecosystems.

1. Introduction

The surimi industry faces several challenges in sourcing and processing raw materials, mainly due to the overfishing of demersal fish species [1]. The labor-intensive nature of the fish-processing industry creates significant vulnerabilities, resulting in calls for alternative raw material sources and a comprehensive understanding of demersal fish stocks to prevent extinction [2,3,4]. Exploring alternative fish species for surimi production is imperative, necessitating detailed studies on the reproductive biology and population dynamics of crucial demersal fish species to address the underutilization of certain fish species as raw materials [5].

The above means that the surimi industry is experiencing unsustainable fishing patterns [4]. Further, this condition emphasizes the need for fundamental technological advancements in the aspects of data collection, sustainable fishing practices, and effective resource management [6]. Therefore, it is vital to determine whether sufficient studies have been conducted and whether the insights from the existing research can guide the surimi industry in managing its raw materials effectively [7].

Recent advancements in fisheries’ sustainability have highlighted the “length-based spawning potential ratio”, or the LB-SPR, as a more precise method to assess fish stocks under data-poor conditions [8,9]. Methodological research on the LB-SPR’s application under conditions of limited data can be seen in case study research on the Persian Gulf [10]. Further, evidence from a study in Palau’s Northern Reef and Sunda Straits in Indonesia supports the existing research. It showcases the snowballing effect of evidence from a previous case study, contributing significantly to the field’s body of knowledge [11,12,13]. These studies demonstrate that the LB-SPR can effectively assess fish stocks in data-poor conditions, highlighting the broader ecological impact and sustainability challenges of overfishing on biodiversity richness [14]. Hence, the body of knowledge on this topic calls for detailed studies on the reproductive biology and population dynamics of crucial demersal fish species [15,16].

However, recent research on this topic has addressed the underutilization of the LB-SPR as a method to assess demersal fish for the surimi industry, as well as the knowledge and methodological gaps in this research topic [17,18,19,20]. Moreover, in addition to these knowledge gaps, the current body of knowledge has also identified the scope of the methodological, practical knowledge, and population issues as types of research gaps that need to be explored more in depth [11,21,22,23,24,25].

Hence, the scope of our study focuses on a methodological discussion of the LB-SPR approach to assessing demersal fish stocks in the surimi industry, without emphasizing any particular geographical areas. According to this scope, our study conducts a comprehensive literature review to explore the methodological aspects and existing implementations that can enhance the quality and scope of the LB-SPR method to improve sustainability in the surimi industry. This study also identifies the existing knowledge and research gaps related to key sustainability-related concepts on utilizing demersal fish in the surimi industry and the LB-SPR method for assessing biological length-based reproduction as a supporting method. Thus, the research questions below support the achievement of this study’s aims:

• What are the knowledge coverage and research gaps concerning key sustainability-related concepts in the utilization of demersal fish in the surimi industry, as well as in the LB-SPR method for assessing biological length-based reproduction as a support method in the surimi industry, and how can these gaps be addressed in future research?
• What aspects of implementation can enhance the quality and scope of the LB-SPR method in assessing reproduction based on biological length, and how can these steps contribute to improving sustainability in the surimi industry?

By applying a PRISMA SLR and thematic analysis, our review emphasizes that reliable data and accurate stock assessments will be crucial for the surimi industry when demersal fish stocks are depleted because of overfishing and unsustainable marine fishing activities [18,26,27]. From our cases studies, the LB-SPR presents a practical and economical methodological solution for managing data-limited fisheries to ensure the long-term sustainability of fish stocks [28,29]. The insights from the LB-SPR may inform relevant stakeholders in the management and development of risk strategies to maintain fish stocks at sustainable levels [9,30].

The structure of our review sequentially presents the background and research objectives, elucidates the analysis methodology, presents the findings, and engages in in-depth discussion, culminating in a comprehensive conclusion. Finally, to construct our study thoroughly, we delve into the background, materials, and methods utilized; carefully examine the results; and explore the significance of raw material management within the surimi industry.

2. Materials and Methods

2.1. Study Design

Within the scope of our research, this review article adopts a positivistic paradigm to achieve the research objectives, a unique approach in this field [31,32]. It employs a qualitative research design with a rigorous systematic process, case studies, and external datasets to comprehensively explore the application of LB-SPR to support the sustainability of demersal fish in the surimi industry [33]. Therefore, using these combined approaches, our review can holistically explore the challenges and opportunities in this topic.

2.2. Data Collection and Materials

The systematic process began with data collection using Scopus and Google Scholar, supported by Publish or Perish (PoP) software [34,35]. These databases were chosen for their comprehensive coverage and access to relevant scientific literature. The data collection process employed the Population, Intervention, Comparison, and Outcome (PICO) and Sample, Phenomenon of Interest, Design, Evaluation, and Research (SPIDER) conceptual frameworks to generate Boolean keywords, as shown in

Table 1. PICO and SPIDER frameworks. Adopted from [36,37].

No.	Framework	Criteria	Keywords	Database Applications
1	PICO	1.1 Populations	“Demersal fish”	Google Scholar, Scopus, and Publish and Perish (PoP)
		1.2 Intervention	“Spawning potential ratio” OR “SPR”	Google Scholar, Scopus, and Publish and Perish (PoP)
		1.3 Comparison	-
		1.4 Outcome	“Surimi Industry”	Google Scholar, Scopus, and Publish and Perish (PoP)
2	SPIDER	2.1 Sample	“Demersal fish” OR “spawning potential ratio”	Google Scholar, Scopus, and Publish and Perish (PoP)
		2.2 Phenomenon of Interest	“Spawning potential ratio” OR “demersal fish”	Google Scholar, Scopus, and Publish and Perish (PoP)
		2.3 Design	“Spawning potential ratio” OR “SPR” or “demersal fish”	Google Scholar, Scopus, and Publish and Perish (PoP)
		2.4 Evaluation	-	Google Scholar, Scopus, and Publish and Perish (PoP)
		2.5 Research type	“Qualitative” OR “quantitative”, “mixed methods”, “literature review”, OR “bibliometric”	Google Scholar, Scopus, and Publish and Perish (PoP)

[36,37].

The PICO framework was utilized to explore populations of demersal fishes, their potential sustainability, their stock assessment status, and outcomes related to the sustainability of these fishes as raw materials used in the surimi industry. On the other hand, the SPIDER framework was employed to generate qualitative insights into the definition of demersal fish stocks, assessment methods, implementation strategies for stock assessment, sustainability of demersal fish stocks used in the surimi industry, and related research gaps.

After generating the relevant keywords, the study applied the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol for inclusion and exclusion criteria to clean the data and refine the scope of the research [38]. The inclusion criteria include English-language research articles that provide necessary information, such as authors, titles, abstracts, or keywords. The exclusion criteria included conference papers, books and its chapters, unpublished articles, and non-English publications. This rigorous data collection and cleaning process ensured that the study was based on high-quality, relevant literature, providing a robust foundation for exploring the sustainability of demersal fish stocks and the implications for the surimi industry [7].

2.3. Literature Selection and Mapping Methods

Our research adopted the PRISMA protocol method to systematically identify, screen, and assess the eligibility of the selected high-quality studies [39]. Then, a cluster analysis was conducted, through a bibliometric approach, to enhance the depth of the analysis using VOSViewer 1.6.19,and the tabulation of selected literature [40]. By focusing on text coherency, ethical consideration, and results, our study assessed the evidence in the selected literature using a critical literature assessment tool [41].

2.4. Analytical Method

Under the guidance of the PICO and SPIDER frameworks, this review used thematic analysis of the selected literature to determine the advantages, definitions, history, and data limitations concerning the surimi industry, demersal fishes, and LB-SPR themes [42,43]. Then, the discussion in this study was strengthened with several case studies and a tabulation of external datasets [32,44,45,46,47,48]. In addition, a research gap taxonomy framework was used to identify our research contribution, the existing body of knowledge’s coverage, and future research directions [21]. Therefore, to synthesize the findings, our study combined these approaches and frameworks to obtain the results using exploratory synthesis in a narrative writing style [49,50].

2.5. Study Framework

Figure 1 shows the framework of this review, emphasizing the shifting processes, from creating research questions and objectives to applying our combined approach. This study developed relevant research questions, objectives, and scopes in the first phase of the review. In the second phase, an appropriate research design, serving as the foundation of our study, continued to be defined. The third phase emphasized the sequential design plan of the methods. Then, in the fourth phase, our study applied the methods sequentially, as designed. By applying this framework, our study could comprehensively and systematically deliver the results.

3. Results and Discussion

3.1. Study Selection, Credibility–Validity Assessment, and Knowledge Cluster Mapping

The study selection process was rigorously conducted using the PRISMA method, initially identifying 960 total records, as seen in Figure 2A. After excluding duplicates, non-English articles, and unretrieved documents, 911 records were assessed for eligibility. This meticulous filtering process focused on peer-reviewed journal articles in English with complete authorship and publication details. Each study underwent a comprehensive review to ensure it met stringent inclusion criteria, including being published in a reputable journal with necessary information such as the authorship, title, abstract, and keywords. This thorough review aimed to select high-quality studies that could provide valuable insights into fisheries management, mainly focusing on sustainability and stock assessment methodologies.

Out of the 909 assessed records, the PRISMA diagram was used to identify 65 studies as relevant. Nevertheless, only 31 studies were included in the ultimate analysis, and the majority were excluded because of the absence of publication dates or inclusion of unrelated topics. This process highlights the importance of rigorous selection criteria in ensuring the quality and relevance of research included in systematic reviews. The remaining studies offer a solid foundation for understanding and improving sustainability assessments in fisheries management, supporting the development of effective and responsible resource management practices. This rigorous approach underscores the necessity of maintaining high methodological standards to ensure the reliability and applicability of research findings in this critical field.

As shown in Figure 2B, the critical appraisal of 65 documents revealed that 52% of the studies clearly stated aims and valid methodologies, demonstrating a solid foundation in research design and execution. This indicates that over half of the studies were well-structured and focused, providing a solid basis for understanding the topics they explored. However, only 9% of these studies adequately considered ethical issues, highlighting a significant area for improvement. Ethical considerations are crucial for ensuring research integrity and societal impact, and this gap suggests a need for more rigorous ethical scrutiny in future studies. Despite this shortfall, the robustness of the studies was evident, with 70% demonstrating rigorous data analysis and clear findings. This methodological rigor ensures that the studies’ conclusions are reliable and valuable for advancing knowledge in the field.

Figure 3 comprehensively shows the interconnectedness of the studies, using a bibliometric analysis in VOSViewer to cluster and map the existing knowledge on the topic. In the context of the LB-SPR method to assess demersal fish stocks in the surimi industry, this clustering and mapping are crucial for advancing the cumulative knowledge on developing effective and responsible fisheries management mechanisms. In this case, Figure 3 reveals the frequent occurrence of the essential keywords, such as “stock assessment”, “marine ecosystem”, “fishery production”, and “physiology”. This indicates that the science of stock assessment that related to the fisheries industry is mostly covered by the environmental nuance, with changing and collaborative landscape characteristics driven by paradigms, policies, and technological advancements.

Table 2 presents a selected-sample thematic summary from 25 high-quality research articles from 65 papers. According to the critical appraisal framework in Figure 2B, this method supported our research in selecting these high-quality articles. As a result, this research focused on the studies’ validity, credibility, and assessment results.

In Table 2, the results of the exploration of each paper, focusing on several correlated topics through thematic analysis, are provided. The first and second topics explore the research papers’ correlations with the subjects of demersal fishes and their sustainability. The third, fourth, and fifth themes sequentially explore the fish stocks’ statuses, the use of technology in the assessments, and the use of length-based spawning potential ratio as a fish stock status assessment method. Lastly, the sixth topic correlates with exploring the fish types discussed in the papers.

Table 2 provides a thematic summary of the implementation of the LB-SPR and its technological development for assessing the sustainability of demersal fish stocks. This table shows that most of the selected high-quality papers consistently focus on demersal fish, but several do not [51,52,53]. The table also illuminates a pattern of the studies: 90% of the research addresses the issue of overexploitation, underscoring the widespread concern about mitigating overfishing in fisheries management.

Table 2 also confirms that the majority of high-quality studies (in addition to [51]) include discussions on identifying fish stock status. Specifically, most of the studies (except [25]) utilize SPR or LB-SPR for fish stock assessment. Moreover, the studies in [12], [54], and [55] show that these methods can be adopted to assess the demersal fish stock. Thus, this proves that SPR and LB-SPR are reliable tools for assessing fish population health and reproduction of all types of fishes [56,57]. Hence, there is a need to increase technological advancements and, thus, the accuracy and efficiency. Accordingly, while few studies do not discuss fish stock assessment technology [54,58,59], a substantial number of studies imply that its implementation and development are crucial for the advancement process [60,61,62,63].

Table 2. Thematic tabulation of several existing studies.

No.	Authors	A	B	C	D	E	F	G	H	I	J
1.	[56]	H	H	VH	V	V	V	V	V		Whitemouth croaker
2.	[57]	VH	M	VH	V	V	V	V	V	V	Red hind
3.	[51]	H	H	VH					V		Striped bass
4.	[12]	M	H	H	V	V	V	V	V	V	Bottomfish
5.	[55]	H	M	H	V	V	V	V	V	V	Red snapper
6.	[54]	H	M	H	V	V	V	V	V		Gag fish
7.	[64]	M	M	MH	V	V	V	V	V		Snappers and groupers
8.	[65]	M	M	MH	V	V	V	V	V	V	Pomadasys kaakan
9.	[52]	M	M	MH		V	V	V	V	V	Short mackerel
10.	[66]	M	M	MH	V	V	V	V	V		Malabar snapper
11.	[53]	M	M	MH		V	V	V	V		Yellowfin tuna
12.	[9]	M	M	MH		V	V	V	V	V
13.	[59]	L	H	MH	V	V	V	V	V		Cod
14.	[16]	M	M	MH		V	V	V	V		Indian scad
15.	[67]	M	M	MH		V	V	V	V		Madidihang
16.	[58]	M	M	MH	V	V	V	V	V		Red drum and red snapper
17.	[68]	M	M	MH	V	V	V	V	V	V	Alaska sablefish
18.	[19]	M	M	MH	V	V	V	V	V	V	Upeneus sp.
19.	[69]	M	M	MH	V	V	V	V	V		Snappers and emperors
20.	[70]	M	M	MH	V	V	V	V	V	V	Mulloway
21.	[25]	M	M	MH		V	V	V		V	White marlin
22.	[61]	M	M	MH	V	V	V	V	V	V	Grouper and snapper
23.	[62]	L	H	MH		V	V	V	V	V	Striped bass
24.	[63]	M	M	MH	V	V	V	V	V	V	Striped marlin
25.	[60]	M	M	MH	V	V	V	V	V	V	Common snook

A: study validity (VH: very high; H: high; M: medium; L: low; VL: very low); B: study credibility (H: high; M: medium; L: low); C: study critical assessment (VH: very high; H: high; MH: medium–high; ML: medium low; L: low; VL: very low); D: does the study discuss demersal fish? (V: yes); E: does the study discuss the overexploitation of fish? (V: yes); F: does the study discuss the sustainability of fish? (V: yes); G: does the study discuss the identification of fish stock status? (V: yes); H: does the research discuss spawning potential ratio and/or length-based spawning potential ratio as a fish stock assessment method? (V: yes); I: does the research discuss using technology for the fish stock status assessment? (V: yes); J: does the research discuss what kind of demersal fish is studied? (V: yes).

Table 2. Thematic tabulation of several existing studies.

No.	Authors	A	B	C	D	E	F	G	H	I	J
1.	[56]	H	H	VH	V	V	V	V	V		Whitemouth croaker
2.	[57]	VH	M	VH	V	V	V	V	V	V	Red hind
3.	[51]	H	H	VH					V		Striped bass
4.	[12]	M	H	H	V	V	V	V	V	V	Bottomfish
5.	[55]	H	M	H	V	V	V	V	V	V	Red snapper
6.	[54]	H	M	H	V	V	V	V	V		Gag fish
7.	[64]	M	M	MH	V	V	V	V	V		Snappers and groupers
8.	[65]	M	M	MH	V	V	V	V	V	V	Pomadasys kaakan
9.	[52]	M	M	MH		V	V	V	V	V	Short mackerel
10.	[66]	M	M	MH	V	V	V	V	V		Malabar snapper
11.	[53]	M	M	MH		V	V	V	V		Yellowfin tuna
12.	[9]	M	M	MH		V	V	V	V	V
13.	[59]	L	H	MH	V	V	V	V	V		Cod
14.	[16]	M	M	MH		V	V	V	V		Indian scad
15.	[67]	M	M	MH		V	V	V	V		Madidihang
16.	[58]	M	M	MH	V	V	V	V	V		Red drum and red snapper
17.	[68]	M	M	MH	V	V	V	V	V	V	Alaska sablefish
18.	[19]	M	M	MH	V	V	V	V	V	V	Upeneus sp.
19.	[69]	M	M	MH	V	V	V	V	V		Snappers and emperors
20.	[70]	M	M	MH	V	V	V	V	V	V	Mulloway
21.	[25]	M	M	MH		V	V	V		V	White marlin
22.	[61]	M	M	MH	V	V	V	V	V	V	Grouper and snapper
23.	[62]	L	H	MH		V	V	V	V	V	Striped bass
24.	[63]	M	M	MH	V	V	V	V	V	V	Striped marlin
25.	[60]	M	M	MH	V	V	V	V	V	V	Common snook

A: study validity (VH: very high; H: high; M: medium; L: low; VL: very low); B: study credibility (H: high; M: medium; L: low); C: study critical assessment (VH: very high; H: high; MH: medium–high; ML: medium low; L: low; VL: very low); D: does the study discuss demersal fish? (V: yes); E: does the study discuss the overexploitation of fish? (V: yes); F: does the study discuss the sustainability of fish? (V: yes); G: does the study discuss the identification of fish stock status? (V: yes); H: does the research discuss spawning potential ratio and/or length-based spawning potential ratio as a fish stock assessment method? (V: yes); I: does the research discuss using technology for the fish stock status assessment? (V: yes); J: does the research discuss what kind of demersal fish is studied? (V: yes).

From the above, our review summarizes that 70% of the current articles demonstrate rigorous data analysis, clear findings, clear aims, and valid methodologies, with a minority of the articles adequately addressing ethical issues. This means that the body of knowledge related to our topic needs further comprehensive enhancement by incorporating ethical considerations, encouraging more empirical studies on reproductive biology, exploring alternative raw materials for surimi production, documenting successful case studies of advanced technologies in fisheries management, and expanding the geographic scope of the review.

According to the current body of research, this review is valuable since it contributes to the accumulation of knowledge by providing a comprehensive understanding of the LB-SPR as a core aspect of assessing demersal fish population dynamics from previous studies. Therefore, stakeholders in the surimi industry can conduct further investigations to evaluate the status of demersal fishes concerning their current and future supplies and seek alternative raw materials using the LB-SPR.

3.2. Sustainability-Related Information in Demersal Fish Stock Assessments for the Surimi Industry

Sustainability in fisheries is critical, particularly for demersal fish stocks, essential raw materials in the surimi industry [29]. As fishing activities increasingly impact these stocks, there is a pressing need for reliable data and regular assessments to ensure their long-term viability [54]. Sustainable stock assessment practices are vital to maintaining the balance of aquatic ecosystems and supporting the continuous supply of high-quality raw materials for the surimi industry [63]. Therefore, based on our study objectives, this review can provide insights into effective management practices that can help preserve fish stocks, ensure the sustainability of the surimi industry, and contribute to the overall health of marine ecosystems.

Fishing activities have significantly impacted demersal fish stocks, crucial raw materials in the surimi industry [26]. Overfishing and unsustainable practices have led to the depletion of these stocks, threatening the balance of marine ecosystems and the long-term viability of the fishing industry [15]. The pressure on these fish populations has reduced reproductive potential and altered species composition, necessitating urgent measures to manage and conserve these vital resources effectively [17].

Reliable data and regular stock assessments are essential for the sustainable management of demersal fish stocks [27]. Accurate stock assessments provide critical insights into the status and trends of fish populations, enabling the development of effective management strategies [18]. Regular monitoring helps detect changes in stock levels early, allowing for timely interventions to prevent overfishing and promote recovery [65]. Without robust data, management efforts will likely be ineffective, potentially exacerbating the decline of fish stocks and jeopardizing the environmental sustainability and fisheries processing industry such as surimi [1,71].

Measures such as catch limits, size restrictions, and seasonal closures have been implemented in various fisheries to mitigate the impact of overfishing [72]. For instance, limiting the numbers and sizes of fishes caught has proven beneficial in maintaining fish populations and allowing stocks to replenish [62]. These management practices, supported by regular stock assessments, help balance exploitation with conservation, ensuring the continued availability of fish for the surimi industry [68].

The quality of the raw materials significantly influences the surimi industry, as the characteristics of the fish used directly affect the manufacturing process and the final product quality [73]. Sustainable stock management ensures a consistent supply of high-quality fish, which is essential for producing superior surimi products [62]. Adherence to good handling practices in fishing and processing, coupled with effective stock management, enhances the quality and sustainability of the raw materials. This, in turn, supports the surimi industry’s growth and contributes to the overall sustainability of marine resources.

3.3. Methodology of Length-Based Reproductive Assessments (LB-SPRs)

Ontologically, the foundation of the LB-SPR method lies in its capacity to represent the reproductive potential of fish populations across different species and environments, which embeds an ethical imperative to sustain marine fish stocks [19,74,75]. This method can address the diverse needs of ecological and operational contexts across multiple stakeholders and different environments, aligning with marine ecosystems’ complex and dynamic natures [74,75].

From an epistemological perspective, this method relies on empirical evidence, comparing observed and expected length distributions in fish populations and interpreting them using scientific models [11]. By grounding its analysis in observable biological traits, the LB-SPR method offers a concrete and empirically driven approach to assessing the sustainability of fish stocks within the broader context of fisheries management [20,71].

This method’s rigorousness hinges on the precision and consistency of the measurements [76]. Thus, sophisticated analytical techniques will be needed to interpret the dynamic fish population data to ensure accurate fish stock assessments [20]. Integrating the LB-SPR method with complementary assessment tools reflects a commitment to comprehensive and ethically responsible fisheries management [17]. By employing a combination of techniques, related stakeholders can better safeguard marine ecosystems while addressing their varied needs effectively and equitably [57,77]. In this case, below is the mathematical function for the LB-SPR and its component functions:

$$\mathrm{Selectivity} \mathrm{function}: S\left(L\right)=1/1+e^{-k_s\left(L-L_{50}\right)}$$

(1)

$$\mathrm{Maturity} \mathrm{function}: M\left(L\right)=1/1+e^{-k_m\left(L-L_{\mathrm{m}50}\right)}$$

(2)

$$\mathrm{Survivorship} \mathrm{function}: N\left(L\right)=N_0\times e^{-\left(M+F\right)\times \left(L-L_0\right)}$$

(3)

$$\mathrm{Length}–\mathrm{frequency} \mathrm{distribution}: N\left(L\right)=N_0\times e^{-\left(Z\left(L\right)L/L_{\infty }\right)}$$

(4)

$$\mathrm{Length}-\mathrm{based} \mathrm{SPR}: LBSPR={\displaystyle \frac{{\sum }_{L=L_{min}}^{L_{max}}N\left(L\right)\times M\left(L\right)\times S\left(L\right)\times L^3}{{\sum }_{L=L_{min}}^{L_{max}}{N}_{unfished}\left(L\right)\times M\left(L\right)\times L^3 }}$$

(5)

The LB-SPR mathematical function integrates several mathematical models that represent its selectivity, maturity, and length–frequency (Functions 1, 2, and 4) [26,65,75,78,79,80]. In this case, the selectivity function (S(L)), as a supporting model of the LB-SPR, is a logistic-based mathematical function that focuses on the length at which 50% of fish are captured (L₅₀) within the slope parameter that controls the steepness of the selectivity curve (k_s) [63,79,81,82]. Then, the maturity function is also a logistic-based function that describes the probability that the fish length (L) is mature and capable of reproducing (M(L)), based on its size at which 50% of fish are mature (Lm₅₀), within the slope parameter that controls the steepness of the maturity curve (k_m) [15,60,83,84]. The length–frequency distribution (N(L)) is constructed with parameters such as the initial number of fish (N0) and total fishing mortalities (Z(L)) [16,60,80,85]. Mortality from fishing includes natural causes (M) and fishing (F), which, in this case, is calculated from survivorship (3) [80,81,83,86].

Critically, all of the above discussions emphasize that this method’s challenges and limitations stem from the complexities of representing fish population dynamics through length data alone [67]. The method underscores the needed quality of collected data to ensure accurate and consistent measurements, which may need to be revised in heavily exploited fisheries, where external pressures alter the accuracies of length-based calculations and reflections of fish population structures [75].

However, this method is still the most appropriate for appraising fish stocks because of its simplicity and use in data-poor assessments [11,12]. This means that the LB-SPR is an adaptive, practical tool with robust cost-effectiveness for data-limited fisheries [11,71]. In addition, this method can provide empirical evidence with ethical, systematic, and scientific nuances that benefits policy frameworks and decision-making processes to ensure the sustainability of fish stocks and the well-being of fishery businesses and communities [84,87,88].

3.4. Case Studies on the Application and Benefits of the LB-SPR

The length-based spawning potential ratio (LB-SPR) method has emerged as a pivotal tool in fisheries management, particularly for data-limited fisheries [28]. By leveraging length data to estimate the reproductive potential of fish populations, the LB-SPR method facilitates informed decision making for sustainable fisheries practices [29]. Its cost-effectiveness and adaptability to various species and regions make it valuable for maintaining healthy fish stocks [75].

Further, the LB-SPR method has not only been successfully applied in assessing demersal fish stocks, which is crucial for the fish-processing industry, such as surimi [8]. For example, studies conducted in the Sunda Strait utilized the LB-SPR method to evaluate the stock statuses of key demersal species [13]. These assessments provided critical insights into these populations’ exploitation levels and reproductive health, guiding effective management interventions to prevent overfishing and ensure sustainable harvesting [29]. Therefore, to provide comprehensive insights, below are examples of case studies related to the collected existing literature.

(1)

Sunda Straits, Indonesia:

The Sunda Strait is a crucial body of water between the islands of Java and Sumatra in Indonesia [13]. This strait has become a significant fishing area for both of the islands, particularly for demersal fish species [14,19]. By using the LB-SPR, recent studies show that high demand and their substantial roles in local and international markets drive the overexploitation of critical and economically vital species, such as red snapper and short-tail mackerel [17,89]. Evaluations in this field also discussed environmental problems, focusing on the fact that most of the caught fish are either immature or young [13,14,19].

(2)

Persian Gulf and Sea of Oman:

In the case of the Persian Gulf and Oman Sea waters, recent studies show that overfishing has weakened the sustainability of juvenile fish stocks over the past two decades [65,90,91]. Using the LB-SPR method, the existing body of knowledge reveals that the javelin grunter fish stock is 20% below the minimum threshold for fish stocks, which indicates severe overfishing and urgent fishing pressure [10,65]. Therefore, recent research has highlighted the importance of fish stock monitoring, stricter fishing regulations, and adjustments in gear usage to allow juvenile fish to reach maturity [91,92].

(3)

Sendangbiru Waters, Indonesia:

The study on tuna resource utilization in the waters of Sendangbiru, utilizing the length-based spawning potential ratio (LB-SPR) method, reveals a critical overexploitation of the tuna population, with an SPR value of just 16.98%, far below the sustainable threshold of 20% [53]. This alarming figure underscores the urgent need for comprehensive fish stock assessment techniques incorporating length, mortality, reproduction, and sex ratios, such as the LB-SPR, to manage fisheries effectively. The case of Sendangbiru vividly illustrates the risks of overlooking these essential parameters, as the current unsustainable fishing practices threaten the long-term viability of the tuna stocks [53]. Adopting and rigorously applying the LB-SPR or similar methodologies could play a pivotal role in reversing these trends and ensuring the preservation and sustainable use of vital marine resources. This case study advocates for the broader implementation of such assessment tools in fisheries management, demonstrating their benefits in maintaining ecological balance and supporting the economic stability of fishing communities [53].

(4)

Palau’s Northern Reefs:

The LB-SPR method was effectively employed in Palau’s Northern Reefs to evaluate the stock status of multiple fish species [11,12]. The Northern Reefs, located within the Pacific Ocean’s coral reef ecosystem, harbor diverse fish species essential for local fisheries [12]. Research in this area has brought attention to the overfishing of multiple species and highlights the broader ecological impact and sustainability of these populations [11]. By applying the LB-SPR method, the recognition of overfished stocks and subsequent conservation recommendations underscore the significance of tailored management practices that account for the distinctive ecological characteristics of coral reef ecosystems [11,12]. As a result, Palau’s Northern Reefs should identify overfished species and implement catch limits and size restrictions [11,12].

(5)

Java Sea, Indonesia:

The Java Sea’s demersal fish species face severe overfishing risks, highlighting the urgent need to adopt the LB-SPR and comprehensive fish stock assessments incorporating length, mortality, reproduction, and sex-specific data. Traditional assessment methods have proven inadequate, as evidenced by studies such as the “Spawning Potential Ratio (SPR) of Sulphur Goatfish” study, which found an SPR of only 7%, indicating a high risk of overfishing [27,73,93]. The “Reproductive Aspects of the Japanese Threadfin Bream” study revealed significant overexploitation, further stressing the need for accurate, data-driven assessments [93]. The “Skipjack Tuna” study demonstrated critically low SPR values of 2–4%, underscoring the failure of traditional methods to protect these species [73]. The “Population Dynamics and SPR of Short Mackerel” study highlights how the LB-SPR can provide essential insights into reproductive status, enabling more effective management [52]. Additionally, research on three dominant demersal fish species in Tegal showed SPR values below 20%, further underscoring the unsustainable nature of current fishing practices that fail to protect both the marine ecosystem and the livelihoods of coastal communities [29,52].

(6)

Blue Swimming Crab Fisheries, Indonesia:

The Blue Swimming Crab fisheries in Indonesia, managed by the Asosiasi Pengelolaan Rajungan Indonesia (APRI), have effectively utilized the length-based spawning potential ratio (LB-SPR) method to monitor and manage stock status [94]. By integrating the LB-SPR into their Fishery Improvement Projects (FIPs), APRI has provided precise stock assessments that inform management practices and industry standards [80,95]. Therefore, the LB-SPR approach has effectively improved stock sustainability in data-limited fisheries, enhancing responsible fishing practices and sustainable resource management [95,96].

(7)

Indonesia Surimi Industry:

The surimi industry in Indonesia has potential for significant growth in the fisheries-processing sector compared to other nations [1]. However, the decline in Indonesian surimi exports from 2020 to 2023 is primarily attributed to overfishing, which has significantly depleted key fish stocks essential for surimi production (see

Table 3. Critical insights of Indonesian surimi product export, constructed from [44,45,46,47].

No.	Production and Export	2019	2020	2021	2022	2023
1	Difference Weight Value of Demersal Fishing Activities for Surimi Material (in MT *):
	- Gulamah	1,031,852	−867,323	696,694
	- Swanggi	2725	12,533	231
	- Kurisi	8448	−4245	11,649	-	-
	- Lencam	1253	627	18,597	-	-
	- Biji Nangka	8615	2665	4795	-	-
	- Gerot-gerot	101	−3313	2032	-	-
	- Beloso	267	−3506	−302	-	-
	- Kerong-kerong	682	−1779	−800	-	-
	- Ekor Kuning	−2541	14,499	−247	-	-
2	Export Volume (in MT)	35,173	31,467	23,643	17,093	14,098
3	Export Frequency	-	1162	880	603	534
4	Export Value (in USD)	82,676,537	88,206,000	69,517,000	61,984,000	51,515,000

* MT: metric tons.

below). These data show substantial reductions in fishing volumes, such as in Gulamah and Biji Nangka, critical for surimi, dropping from 1,031,852 tons and 8615 tons before 2020 to 696,694 tons and 4795 tons in 2021, respectively. This reduction in raw material availability has led to a corresponding decline in surimi export volumes from 31,467 tons in 2020 to 14,098 tons in 2023. The over-exploitation of fish stocks has strained the industry’s ability to sustain production levels and meet export demands, underscoring the critical need for sustainable fishing practices to restore and maintain fish populations [77,97].

Therefore, access to accurate information on raw material is vital for making informed management decisions to support Indonesia’s surimi exports’ long-term stability and growth [53,54]. Sustainability in fisheries, especially for demersal fish stocks, is crucial as they are vital raw materials for the surimi industry. Considering the increasing impact of fishing activities on these stocks, reliable data and regular assessments are urgently needed to ensure their long-term viability. Emphasizing sustainable stock assessment practices is essential for maintaining aquatic ecosystem balance and providing a continuous supply of high-quality raw materials for the surimi industry.

(8)

Kuwaiti Waters:

The application of the length-based spawning potential ratio (LB-SPR) in this study provided significant advantages in assessing the reproductive sustainability of Otolithes ruber in Kuwaiti waters [98]. The LB-SPR is particularly suited for data-limited fisheries, as it estimates the spawning potential based on the lengths of the fish, bypassing the need for extensive age data. This method allows for a precise evaluation of the impact of fishing pressure on the species’ ability to maintain its spawning potential, offering insights for more effective fisheries management to sustain healthy reproduction levels [98]. In this case, the use of the LB-SPR supports the regulation of fishing activities and long-term viability of Otolithes ruber to ensure its continued commercial value in Kuwaiti waters, and to the sustainability of the regional fishery [98].

(9)

Liberia Coastal Waters:

Liberia’s fisheries sector is recovering from the impacts of civil conflict [99]. Meanwhile, the sustainable management of demersal fish stocks is essential for Liberia’s food security, poverty alleviation, and economic growth [99]. Hence, efforts to recover have focused on improving fish stock monitoring, capacity building, and infrastructure development in coastal and marine areas around Monrovia and other fishing communities [100]. Strategies to achieve this include enhancing data collection and analysis, upgrading infrastructure, building capacity for sustainable practices, strengthening enforcement against IUU fishing, fostering international collaborations, and providing financial support to small-scale fisheries [101].

3.5. Multi-Aspect Implications of LB-SPR: Fisheries Business, Communities, and Policies

Integrating the LB-SPR into business management promotes sustainable practices throughout the supply chain in fisheries and fish-processing business management [18,22,73]. This method is critical for aligning industrial practices with a long-term sustainable and consistent supply of fish, such as the implementation of selective fishing gear [24,63,69]. By setting scientifically informed thresholds for fish catches, businesses can mitigate the risk of depleting stocks and ensure the long-term viability of their investments in sustainable technologies and practices [23,52,80].

Adherence to sustainable catch limits and size regulations informed by the LB-SPR aligns with consumer demand for responsibly sourced seafood [11,102,103]. This alignment supports the industry’s commitment to sustainability and opens new market opportunities as consumers increasingly seek out environmentally responsible products [26]. In this case, the fish-processing industry, especially sectors like surimi production that depend on specific demersal fish species, benefits significantly from applying the LB-SPR [1,5,14]. Although fishing activities may be adjusted initially, the method ultimately ensures a consistent and high-quality supply of raw materials without contributing to overfishing [69,104]. By applying the LB-SPR, the industry can better manage the size and quality of the fish processed, enhancing product quality and market competitiveness [68,105].

The LB-SPR method is also crucial in sustaining the livelihoods of fisheries communities that rely on healthy marine resources [9,26]. While implementing the LB-SPR might initially reduce unsustainable fishing activities, it ultimately ensures that fishing practices are sustainable, protecting the long-term viability of fish stocks [69,104]. This protection is vital for maintaining the economic stability of fisheries communities, where the health of local fish populations is directly linked to community well-being [106]. In addition, to mitigate the potential impact of reduced fishing activities due to LB-SPR implementation, the fish processing industry can turn to land—and marine-based aquaculture as a viable solution for providing raw materials and a significant livelihood solution for fisheries communities [107,108,109,110].

On the one hand, land-based aquaculture systems, such as recirculating aquaculture systems (RAS), allow for fish production even in communities that do not rely on wild stocks, reducing pressure on marine ecosystems [69,111,112]. This shift can help maintain income levels and provide economic stability, as traditional fishing activities may decline because of stricter regulations [69,104]. On the other hand, marine-based aquaculture, including offshore fish farming, can also play a significant role in supplementing the supply of fish, especially for species that are difficult to cultivate with land-based systems [109,110]. This aquaculture, including coastal and offshore fish farming, offers a viable alternative for communities to continue fishing while contributing to sustainable practices [106,113]. By investing in and expanding aquaculture operations, the fish-processing industry can ensure a reliable and sustainable supply of raw materials, and fishery communities can support the long-term sustainability of their livelihoods, even as LB-SPR-driven regulations may limit certain fishing activities [106,114].

The LB-SPR provides a scientific foundation for setting size and weight regulations, which are essential for maintaining healthy fish populations [96,115,116]. By determining the length at which fish are most likely to reproduce, policymakers can establish minimum size limits that ensure fish have had the opportunity to contribute to the next generation before being harvested [65,72]. This approach is crucial for preserving fish populations’ reproductive capacities and preventing overfishing, even if it means adjusting current fishing practices [12,61,70].

The LB-SPR method is instrumental in helping establish biologically informed catch limits that align with the reproductive potential of fish populations [12,18,86]. By assessing the length-based data of fish populations, the LB-SPR can accurately determine how much fish can be sustainably harvested without compromising their ability to reproduce and replenish their numbers [9,91]. Although this might involve reducing fishing activities in the short term, creating a sustainable balance between fishing activity and the natural capacity of fish populations to recover is necessary [9,26]. This approach prevents overfishing and ensures that fish populations remain stable over the long term [12,61].

LB-SPR is an invaluable tool for identifying the need for protective measures in areas where spawning occurs and also the recovery times for depleted fish populations to return to sustainable levels [9,12,91]. By analyzing length-based data, the LB-SPR can pinpoint regions where spawning activity is significant and where fishing pressure may need to be reduced or restricted or even insights into the rate at which fish populations can recover under different management scenarios [96,115,116]. These insights are vital for policymakers to implement targeted seasonal closures, establish marine-protected areas, and adjust fishing activities, ensuring that spawning grounds are preserved and that fish populations can sustain themselves [115,116].

3.6. Contribution to the Field, Gaps, and Recommendations for Future Research

Our exploration of the collected literature found that most studies included a theoretical discussion under a taxonomy of gaps in the research [21,51,56,70,81,105,117,118]. Empirical and evidential research followed as the second- and third-most covered research gaps [25,69,82,102,119]. However, there are still many unknown areas in the aspects of knowledge, methodology, population, and practical knowledge discussions [55,83,120,121]. This means that the knowledge on the topic covers only theoretical-, empirical-, and evidence-based insights.

The above realities are our logic for consolidating the knowledge gaps in the LB-SPR method as a novel contribution. To capture the knowledge gaps, our study focused on the detailed aspects of the LB-SPR, which indicates the need for more fish sampling in real-life experiments and for considerations from multiple aspects [11,12,18,79]. Detailed studies on the reproductive biology and population dynamics of crucial demersal species are essential to enhance the accuracy and reliability of stock assessments [24,64,85]. This necessitates a concerted effort to bridge existing knowledge gaps and further explore the potential of the LB-SPR for demersal fish within the surimi industry [1,11,122,123,124].

Research on demersal fish species needs historical life data and cohort analyses to identify critical periods for conversation efforts [57,60,64,77]. In this case, advanced sampling, data collection technologies, and deterministic and biological models that consider factors like sex and age-specific growth rates can contribute to more precise assessments and management strategies [15,54,118]. Therefore, Figure 4 captures these aspects for future research agendas and coverage in the current study, highlighting how multidisciplinary aspects and stakeholders can address the overexploitation of demersal fish stocks and enhance the sustainability of the surimi industry [17,26,68,107].

Finally, several vital recommendations exist to improve the comprehensiveness and quality of future research. They are (1) incorporating a section on ethical considerations, (2) encouraging more empirical studies on reproductive biology, (3) exploring alternative raw materials for surimi production, (4) documenting successful case studies of advanced technologies in fisheries management, and (5) expanding the geographic scope of this review. By integrating these suggestions, future reviews can provide a more comprehensive resource for researchers and practitioners in the surimi industry and fisheries management.

4. Conclusions

This study aimed to achieve two primary objectives. The main goal was to review the existing literature to identify knowledge and research gaps related to sustainability concepts on the use of demersal fish in the surimi industry and the LB-SPR method for assessing biological length-based reproduction. Another aim was to improve the LB-SPR method’s quality and breadth in assessing reproduction and to explore how these measures can enhance sustainability in the surimi industry. Guided by these objectives, the research focused on two key questions on the identification of the body of knowledge, gaps, and future research agenda of the topic and exploring the aspects of implementation that can enhance the quality and scope of the LB-SPR method, contributing to improved sustainability in the surimi industry.

In this review, a comprehensive literature review conducted using the PRISMA protocol was crucial in gathering and analyzing the data. The review employed the PICO and SPIDER frameworks to source relevant literature and utilized VOSViewer for bibliometric analysis. Case studies included in the review demonstrate the practical application and benefits of the LB-SPR method in various contexts, emphasizing the importance of reliable data and tailored management strategies for sustainable fish stocks and the surimi industry.

To address the challenges faced by the surimi industry due to overexploitation and fishing restrictions, the study suggests prioritizing sustainable practices through the expanded use of the LB-SPR method, integrating advanced technologies for better stock assessments, and adopting effective management strategies, such as catch limits, size restrictions, and seasonal closures. By implementing these practices, the surimi industry can achieve sustainable development, ensuring the long-term viability of demersal fish stocks and the health of marine ecosystems. This comprehensive approach supports the industry’s economic stability and contributes to global efforts in marine conservation and sustainable resource management.

Concerning the practical knowledge and population research gaps, empirical studies with robust data sampling and embedded with interdisciplinary research need to cover many unknown areas in the body of knowledge. In conclusion, future research should incorporate ethical considerations, encourage empirical studies on reproductive biology, explore alternative raw materials for surimi production, and document successful case studies of advanced technologies in fisheries management.