Two species of macroalgae (Undaria pinnatifida and Gracilaria vermiculophylla) collected from the Russian Far-East were evaluated in laboratory experiments to determine their potential as biofilters. For this purpose, their nutrient uptake potential and their physiological response to wastewater effluents from a maricultural rearing system (mussels’ culture) were measured.

8 g (fresh weight) of macroalgae were placed by replicate in 2 L containers with a continuous flow of wastewater. Water samples were taken to measure the ammonium- and phosphate concentrations and calculate the nutrient uptake rate. During the experiments, the temperature was maintained at 15°C, the irradiance was fixed at 130 µmol photons m^-2 s^-1, and the aeration was supplied continuously.

The results obtained indicated that both species of macroalgae can reduce the nutrient concentrations in the water (up to 70-90% of ammonium and 35-82% of phosphates). Besides, any negative effect on the growth and physiological conditions of both macroalgae species were found.

The study suggests that both species have great potential as a biofilter. Furthermore, the macroalgae species tested have great economic potential, being another good reason to use in IMTA.

For more details please visit: Skriptsova and Miroshnikova (2011). Laboratory experiment to determine the potential of two macroalgae from the Russian Far-East as biofilters for integrated multi-trophic aquaculture (IMTA). Bioresource Technology 102, 3149-3154.

The bait which is an integral part of the coastal life is often perceived as a low-value resource due to limited fisheries data, locally focused, and largely unregulated. A wide range of marine invertebrates can be used for bait depending on the season, personal preference, and the species to be caught, but in nearly all locations, intertidal soft-sediment polychaetes are the dominant group collected. Generally, commercial and semi-professional fisheries for polychaete worms supply the regional and international markets for bait worms for recreational fishing. There is also a direct harvest of polychaetes from the wild by recreational fishers which is generally accepted to be a substantial portion of the total harvest. The first global assessment of polychaete bait fisheries was manifested based on an empirical assessment of three UK-based ragworm fisheries combined with an analysis of published literature. According to this assessment, the five most expensive (retail price per kg) marine polychaete species sold on the global fisheries market are (Glycera dibranchiata, Diopatra aciculata, Nereis (Alitta) virens, Arenicola defodiens and Marphysa sanguinea). With approximately 121 000 tonnes of polychaetes collected globally valued at £5.9 billion, it was estimated that 1600 t of N. virens per annum (worth £52 million) are landed in the UK alone. Activities of collectors at local collection sites monitored using remote closed-circuit television (CCTV) cameras showed considerable activity with a mean of 3.14 collectors per tide (day and night) at one site. Moreover, individuals were digging for up to 3 h per tide, although intensity differed seasonally and between sites. Collectors usually walked considerable distance across the intertidal sediment to reach areas that were usually already dug and collect on average 1.4 kg of N. virens per person per hour. In addition, the demand for wild-caught polychaetes could surge as an ever-expanding aquaculture industry increases polychaete consumption for use as maturation diets for broodstock and to offset stagnations in the supply of fish meal and fish oil. To ensure sustainability and to minimize the environmental impacts of coastal regions, urgent action is required against wild biomass collection. Within the context of fisheries and conservation management, the implications of these human activity and biomass removal levels are explored. Polychaete bait fisheries are highly valuable at the local, regional and national scales. Removal of significant biomass from the wild might have considerable impacts and therefore, urgent governance equivalent to other fisheries is the need of the time.

For more details please visit the link: Bait worms: a valuable and important fishery with implications for fisheries and conservation management

Though the potential of polychaetes has not been fully investigated, they are known to function as organic extractive species in IMTA systems. Owing to the high levels of polyunsaturated fatty acids (PUFAs) found in several polychaetes species it is worthwhile to explore the practicability of employing polychaetes to convert fish farm waste into alternative resources for fish diet. Within this context, Nederlof and his team evaluate the potential of polychaetes Capitella sp. and Ophryotrocha craigsmithi to convert fish waste into valuable ingredients for fish feed formulation. The polychaetes were fed different forms of salmon feces (fresh, acid-preserved, or oven-dried) and their production rate as well as body composition, especially, fatty acid (FA) profiles were determined to evaluate their applicability in (de)coupled integrated multi-trophic aquaculture (IMTA) systems. Coupled production involves direct integration of polychaetes and fish within the same eco (system), whilst in decoupled production, the rearing units can be separated spatially or functionally. Preservation of fish waste is recommended in case of decouple system. The authors observed the highest growth rate in both species when fed with fresh feces, whilst a negative growth rate was observed in O. craigsmithi when fed with preserved diets. This in fact suggests the importance of microbial role in polychaetes’ diet. Despite relatively low content of PUFAs (5-9% of total FAs) in the diets, the fatty acid profile showed that both species were rich in PUFAs (>30% of total FAs). Moreover, all essential FAs needed for fish nutrition were also found. The FA profile was enriched in Capitella sp. when fed acid-preserved diets. The enriched levels of FAs found in both species might be accredited to the accumulation of PUFAs, de novo synthesis and/or transfer via bacterial biomass that could have led in the up-regulation of PUFA content. On the whole, the authors conclude that both species are highly valuable marine products that can be used as an alternative source for fish food formulations. Deducing from the recorded growth rates with different diets, O. craigsmithi seems more suitable for integration in coupled systems where fresh fish feces are continuously supplied, whilst Capitella sp. is interesting for both coupled and decoupled integrated systems as favourable growth was observed on all diets tested.

For more details please visit: Application of polychaetes in (de)coupled integrated aquaculture: production of a high quality marine resource

Polychaetes, generally are marine annelid worms that have gained popularity owing to their use as baits both for recreational and professional fishing purposes. In addition, it can also contribute to aquaculture diversification. Though polychaete culture has been feasible and commercially attempted too, managing polychaete fisheries has progressed only in few countries around the world. Those countries with no marine polychaetes production either depend upon wild harvest or imports. An in-depth study is needed to provide a better understanding of the nutritional requirements and reproduction of some species. Nevertheless, new technical improvements that can lead to significant progress in productivity and give fresh momentum to the polychaete production have been demonstrated. Amongst the marine worm species, a few were recognized as good candidates for integrated multitrophic aquaculture.  Within this aspect, the development of rearing techniques and grow-out procedures are the central points. This will allow the culture of new polychaetes, possible in polyculture systems that can enhance aquaculture sustainability, reduce environmental threat and increase earnings. Considerable environmental benefits might be gained by increasing bait farming and reducing bait-digging activity. Moreover, many anglers would prefer to purchase cultured bait rather than dig their own, provided the supplies were of high quality and priced advantageously with respect to some of the worms collected from the wild. Additionally, some worms are also regarded as one of the most important components in order to maintain a thriving sand bed. They are excellent scavengers and detritus consumers. Their activity turns over the upper layers of aquarium sand beds, working detritus into the sand, thereby preventing clumping. Furthermore, the demand for polychaetes has increased as a result of their use to feed other species in aquaculture as it ensures adequate nutrition for reared broodstock. Last but not the least, polychaetes are also extensively used for research purposes, as model animals, for instance in reproduction, ecotoxicology, bioremediation, and environmental monitoring studies. Substantial work focused on the main technical improvements and advances have been made in areas as varied as polychaetes’ aquaculture potential, reared species, main species used worldwide, highlights biological and ecological concerns, important challenges and recommendations.

For more information please refer:Insight into aquaculture's potential of marine annelid worms and ecological concerns: a review

Polychaetes and their potential use in aquaculture

Aquaponics is the integration of aquaculture and hydroponics in a recirculating system. This production model has been successfully developed around the world using freshwater. However, in recent years and due to the development of the cultivation of salinity-tolerant plants, various studies have been carried out to evaluate the production of marine species coupled to halophyte plants.

Researches from the Federal University of Santa Catarina Brazil evaluated the integrated culture of Pacific white shrimp (Penaeus vannamei) and Sarcocornia ambigua in a marine aquaponic system with biofloc. The experimental system consisted of an 800 L culture tank, a 40L conical bottom chamber, and an NFT hydroponic system with 0.4 m2 of planting area. The shrimp culture was stocked at 250 shrimp m^-3 and 40 plants were coupled in each system. The experiment was carried out for 74 days.

The final plant production obtained was 8.2 kg m^-2 while the final shrimp biomass was 2.1 kg m^-3. The water quality was maintained within the acceptable limits for marine shrimp culture. The recovery of nitrogen supplied to the aquaponic system was higher (39.3%) than a similar system without plants (31.4%).

The proposed system is capable to produce 2 kg of plants for each kilogram of shrimp produced. The present study shows the feasibility of produce shrimp and plants using marine water, while the use of nutrients is improved.

For more details, see: Pinheiro et al. (2017). Production of the halophyte Sarcocornia ambigua and Pacific white shrimp in an aquaponic system with biofloc technology. Ecological Engineering 100, 261-267.