Author: Javier Velasco

One of the main challenges of modern Aquaculture is reducing the use of Fish Meal and Fish Oil on fish feed by introducing new ingredients and maintaining the quality of feeds as well as the performance and welfare of fish.

DIBAQ, following its innovative policy and with the aim to produce more sustainable and functional feeds, carried out the project FISHUB, funded by APROMAR (Spanish Aquaculture Corporate Association).

The main goal of the project It’s been to develop new functional diets, more sustainable and with a high productive and immune performance in aquatic species by introducing, in commercial formulas, fermented soybean meal.

To that end, we carried out three trials with three of the main commercial species of the medietrranean aquaculture such as Sole (Solea solea), Seabream (Sparus aurata) and Seabass (Dicentrarchus labrax).

Each trial were 18 weeks long. We tested a control diet (Diet B) versus two experimental diets replacing fish meal with different inclusion levels of fermented soybean meal (Diet A 50% inclusion and Diet C 25% inclusion). Always tried to keep the control nutritional profile on diets A and C; same protein profile and same fatty acids profile (EPA & DHA).

These trials showed similar results, both in nutritional and immune trials, for the three species. No significant statistical differences were found but for control diet and high inclusion of fermented soybean diet that showed a minimum slight difference in performance with better results.

	Dieta A	Dieta B	Dieta C	P valor
Peso inicial (g/ind)	30,94±0,80	29,95±0,4	30,34±0,88	0,090
Peso final (g/ind)	103,65±4,13	104,21±3,72	102,18±2,78	0,609
Incremento de peso (g)	72,72±3,46	74,26±3,7	71,84±2,33	0,439
SGR (%/día)	1,44 ± 0,03	1,48 ± 0,04	1,45 ± 0,03	0,134
FCR	1,52 ± 0,06 ab	1,49 ± 0,05 a	1,58 ± 0,04 b	0,015
k	2,93± 0,05	2,86 ± 0,08	2,93 ± 0,05	0,171
Supervivencia (%)	97,78 ± 2,72	98,33 ± 1,83	98,89 ± 1,72	0,734
Índice Hepatosomático	2,10± 0,2	1,95 ± 0,22	2,33 ± 0,63	0,367
Ingesta total de alimento (g)	3287,25 ± 194,62	3282,92 ± 115,50	3391,78 ± 92,54	0,345

Table 7:  Performance data for Sea Bream

Nota: SGR = Specific Growth Rate; FCR= Feed Conversion Rate; K= Fulton’s condition factor.

Results of pathological challenge carried out in Seabass against the bacteria Photobacterium damselae subsp. Piscicida, also showed no significant differences between three diets but for a slight worst performance on diet with less inclusion level of fermented soybean meal.

Figura 4. Cumulative Mortality fo Diets A, B & C. during the Challenge.

As conclusion, showing the three trials results, referring performance rates, optimum growing rates, and normal range of conversion rates, replacing fish meal in commercial diets with fermented soybean meal could have a positive impact on feed manufacturing, keeping performances on good levels without damaging fish immune and welfare condition.

The incorporation of high-energy diets in the aquaculture industry has become a common practice to enhance growth and productivity. However, recent studies have shed light on the potential risks associated with excessive lipid levels in fish diets. Understanding and mitigating these effects is crucial to ensure the health and economic viability of farmed fish.

Understanding the Risks:

While moderate levels of lipids can boost fish performance in the short term, excessive levels can lead to a myriad of undesired impacts. These include excessive growth without skeletal support, impaired liver function, diminished antioxidant capacity, and weakened immune function. Moreover, these diets have been linked to lipid accumulation in viscera, endoplasmic reticulum stress, and suppression of autophagy in fish liver. Additionally, they can disrupt the intestinal barrier, triggering inflammation, metabolic disorders, oxidative stress, and microbiota imbalance.

Mitigation Strategies:

Fortunately, there are several approaches that can help mitigate the adverse effects of these diets on farmed fish. Dietary manipulation stands out as a key strategy, involving adjustments in the composition of fish diets to alleviate the negative impacts of excessive lipid intake. This includes reducing blood lipid levels, attenuating oxidative stress, and improving immune function and antioxidant activity in fish.

Role of Feed Additives:

In addition to dietary adjustments, the use of feed additives has shown promising results in mitigating the risks associated with high-lipid diets. Supplements such as herbs, medicines, acids, minerals, and certain vitamins have been found to modulate lipid metabolism and enhance the endogenous antioxidant defense mechanism in fish. These additives play a crucial role in altering cellular signaling activities, thus offering indirect protection against the adverse effects of high-lipid diets.

Our Commitment at Dibaq Aquaculture:

At Dibaq Aquaculture, we prioritize the health and well-being of fish. Each high-energy diet is meticulously designed, drawing upon our extensive experience and scientific research. We take into account the latest findings in aquaculture nutrition to ensure that our diets optimize fish performance while mitigating the risks associated with high lipid intake.

Lactococcus garvieae is considered the main etiological agent of lactococcosis, a globally distributed disease characterized by haemorrhagic septicaemia in aquaculture species, leading to significant economic losses. The history of pathogenic Lactococcus garvieae clones for fish, dates back more than three decades, when it was first described following a septicaemic outbreak in Japan in marine Seriola fish farms (Seriola quinqueradiata), initially classified as a new enterococcus species (Enterococcus seriolicida).

Subsequently, outbreaks began to appear in freshwater fish farms in Japan (Japanese eel, Anguilla japonica) (Kusuda et al. 1991) and in Europe in rainbow trout (Oncorhynchus mykiss). The disease caused by this bacterium in fish showed signs like exophthalmia, petechiae on the opercula, and congestion of the pectoral and caudal fins. The similarity in clinical presentation and characteristics of this new strain with infectious outbreaks in freshwater fish farms in Spain, led to a comparative analysis of the bacterial culture characteristics, biochemical profile, and protein composition of both bacteria. This analysis provided phenotypic and phylogenetic evidence for reclassifying Enterococcus seriolicida as Lactococcus garvieae (Doménech 1993).

Several co-authors of this study belonged to the Department of Animal Health at the Veterinary Faculty of the Complutense University of Madrid. It was in this department, and later also at the Veterinary Health Surveillance Centre (VISAVET – UCM), where the first autogenous vaccines against L. garvieae were successfully developed. These vaccines were distributed in collaboration with DIBAQ Group to many freshwater fish farms in Spain where this infectious disease was present, significantly reducing its prevalence through this prophylactic measure. This work in vaccine development and the epidemiological and molecular characterization of L. garvieae was recognized and awarded with the first Jacumar Award for Research in Aquaculture by the Ministry of Agriculture, Fisheries and Food in 2001. Since then, numerous studies on this pathogen have been conducted by the research group from the Department of Animal Health, VISAVET, and DIBAQ Group, focusing on its phenotypic and molecular characterization (Vela 2000, Aguado-Urda 2010), its isolation from different animal species (Garcia 2001, Tejedor 2004, Tejedor 2008), comparison of isolates from different animal species and countries (Tejedor 2011), its zoonotic potential (Reguera-Brito 2016, Gibello 2016), development of detection techniques (Tejedor 2009, Perez-Sancho 2015), and studies on antimicrobial sensitivity (San Martin 2017, 2018, 2019).

At the international level, the publication of studies on this pathogen in the aquaculture sector is extensive, with publications confirming its worldwide distribution (Eldar 1999), studies on the epidemiology of the infection in relation to isolated strains (Eyngor 2004), immune response to the infection and comparisons among asymptomatic, symptomatic, and vaccinated animals (Ooyama 1999, Khalil 2023), various studies on genetic and phenotypic characterization (Morita 2011, Shahi 2020, Rao 2022), antimicrobial resistance (Maki 2008, Akmal 2023), susceptibility to infection (Algöet 2009), development of detection techniques (Tsai 2013), supplementation with probiotics or bacteriocins as a preventive measure (Sequeiros 2015, Baños 2019), vaccination (Hussein 2023), and review articles establishing L. garvieae as an emerging pathogen in aquaculture (Meyburgh 2017).

The concern created by this pathogen in aquaculture is further compounded by the description of Lactococcus petauri in 2017 from an abscess in a sugar glider (Goodman 2017). Since then, numerous publications have identified this new species as responsible for lactococcosis outbreaks in continental fish farms instead of the previously isolated L. garvieae (Kotzamanidis 2020, Altinok 2022, Vela 2024). Consequently, studies on L. petauri have focused on its identification (Catao 2023, Stoppani 2023), characterization at different levels, mainly to find differences between L. petauri and L. garvieae (Saticioglu 2023), pathogenicity (Catao 2023), vaccination strategies (Ruyter 2023), and evaluation of its zoonotic potential (Vendrell 2006, Martinovic 2021).

Recently, outbreaks of lactococcosis caused by L. garvieae in marine species such as sea bass (Salogni 2024), have set off the alarm about a new emergence of this pathogen. The genetic differences from other epidemiologically related strains and the pathogen’s resistance to antimicrobial treatment, underscore the importance of vaccination against L. garvieae as a crucial tool for controlling this disease. And once again, at DIBAQ, we are prepared to take on the challenge and provide scientific solutions to the problems that Aquaculture has to face.

Introduction

South Korea, a nation with a long maritime history, has seen significant growth in its aquaculture industry in recent decades. Aquaculture plays a crucial role in the South Korean economy, providing food, employment and contributing to international trade. Dibaq has been working on the future challenges of aquaculture in South Korea for years.

The history of aquaculture in South Korea dates back centuries, with traditional practices of growing fish and shellfish in ponds and shorelines. However, it was in the second half of the 20th century that aquaculture began to develop as a modern industry. Government development programs and advanced technologies enabled rapid and significant expansion of the industry.

Today, South Korea is one of the main aquaculture producers worldwide. The industry focuses on farming fish, shellfish and algae, with species such as abalone, shrimp and flatfish being the most common. Advanced technology, scientific research and sustainable management practices have contributed to the success of South Korean aquaculture.

AQUACULTURE	Tons2​	%2​
Seaweed	764 913	60.7
Shellfish	391 060	31.1
Fin fish	91 123	15.2
Others	12 128	0.9
Total	1 259 274	100

Dibaq works in Korea with products for salmon, trout, mullet, flatfish. In addition, it exports functional feed for bream, salmon and trout.

Future Challenges and Opportunities

Despite its success, aquaculture in South Korea faces several challenges. Water pollution, competition for coastal space, and fish disease are major concerns that require innovative solutions. Additionally, climate change presents additional challenges, such as rising water temperatures and extreme weather events.

There is growing concern that pollution could affect fishing and aquaculture production14 due to the recovery works and construction of industrial complexes in the southern and western coastal districts of the country.

Recently, integrated aquaculture management has created an alternative plan to overcome problems such as red tide, typhoon and pollution caused by human activities.6 In this plan, the scope of “aquaculture land” extends to the open areas. It is divided into three subdivisions: terrestrial aquaculture, polytrophic aquaculture and offshore aquaculture, which are relatively new concepts in the Korean aquaculture industry.

However, there are also exciting opportunities for the future of aquaculture in South Korea. The development of sustainable technologies, such as aquaponics and offshore aquaculture, could increase productivity and reduce environmental impact. Additionally, growing global demand for seafood offers an expanding market for South Korean producers.