Search

Algae, including seaweeds and microalgae, contribute nearly 30 percent of world aquaculture production (measured in wet weight), primarily from seaweeds. Seaweeds and cmicroalgae generate socio-economic benefits to tens of thousands of households, primarily in coastal communities, including numerous women empowered by seaweed cultivation. Various human health contributions, environmental benefits and ecosystem services of seaweeds and microalgae have drawn increasing attention to untapped potential of seaweed and microalgae cultivation. Highly imbalanced production and consumption across geographic regions implies a great potential in the development of seaweed and microalgae cultivation. Yet joint efforts of governments, the industry, the scientific community, international organizations, civil societies, and other stakeholders or experts are needed to realize the potential. This document examines the status and trends of global algae production with a focus on algae cultivation, recognizes the algae sector’s existing and potential contributions and benefits, highlights a variety of constraints and challenges over the sector’s sustainable development, and discusses lessons learned and way forward to unlock full potential in algae cultivation and FAO’s roles in the process. From a balanced perspective that recognizes not only the potential of algae but also constraints and challenges upon the realization of the potential, information and knowledge provided by this document can facilitate evidence-based policymaking and sector management in algae development at the global, regional and national levels.

Recreational fishing is an increasingly popular hobby both locally and globally. This rise in popularity has increased the global demand for bait and has resulted in a higher demand for bait-worms than can be supplied. Bait-worms are a highly valued resource with a price tag, which is often higher per kg than that of human food. Evidence from overseas indicates that recently three main avenues have been adopted to fill this deficit 1) the culture of bait-worms, 2) the importation of live or preserved bait-worms or 3) by increasing the intensity of wild harvest (which has led to the development of a black market in Europe). None of these avenues has thus far proven sufficient to meet the current bait-worm deficit. Australia is currently mirroring the worldwide bait-worm situation, but to a much lesser extent, so is in the enviable position of being able to address the issue before it becomes dire, as has occurred in many parts of Europe and the USA. Of the three main avenues attempted overseas, only two realistic options are available for Australia and indeed South Australia as our strict quarantine laws preclude the importation of live bait-worms. The two remaining options are to increase the intensity of wild harvest and/or to culture bait-worms. There appears little chance of increasing commercial wild harvest for various reasons discussed in this report, so the development of a culture industry may be the most viable means of addressing the bait-worm deficit. Before considering the development of such an industry, it is imperative, and pertinent, to assess the current and potential markets for both live and preserved bait-worms within South Australia to assess the need for the end product. To this end, a survey was developed, distributed and the findings reported here. This survey was distributed to 92 retailers and 25 (27%) surveys were returned.This survey has identified that: • there is likely to be a market for aquaculture derived worms: 64% of baitshop owners would use a regular source of live worms with >85% of shop owners may prefer cultured worms to wild harvested • approximately 73% of anglers buy their worms from baitshops - which could equate to approximately 225,000 South Australian recreational anglers based on the 2000 - 2001 SA regional version of the National Recreational and Indigenous Fisheries Survey and ~$100 million of funds for fishing related expenses • the responding baitshop owners estimated potential sales of live worms was approximately 1.25 tonnes in the first year. The survey respondent’s sales accounted for only 15% of the total wild harvested bait–worms in the year surveyed, so the above estimate is probably conservative. The potential sales for preserved bait-worms was not assessed.

The first experiment of this study analysed the influence of genotype on this sexual dimorphism growth through comparison of different males genotypes: YY 100 (YY male x YY female), XY 100 (YY male x XX female), XY 50 (XY male x XX female) and XX 100 (sex reversed males). The objectives of the second experiment were to study the influence of social interactions through the use of different sex-ratios: F100, F75, F50, F25, F0 (F100 = % of females in the population). These two experiments were realised in hapas implanted in pond with "Egypt-UCS" strain of #Oreochromis niloticus#. At the end of the first experiment (140 days post-fertilisation), the genotype XY (100 or 50) present the best growth performances and genotype YY the lowest. Final body weight of sex-reversed male (XX 100) were significantly higher the XX 100 females and YY 100 males. There is no significant difference between YY 100 males and XX 50 females. According to our results, the involvement of a genetic component in sex-related growth difference between males and females is strongly suspected. We stressed upon the involvement of genes bound to the sexuel genotype (especially XY in comparison to YY and XX) independently of the sexuel phenotype. From 102 days post-fertilisation until the end of the second experiment, females of F25 population present the best growth performances. Their final body weight were significantly higher than those of all the males except F50 population males. In general, females body weight tend to increase inversely to their number in the population. Males of F50 population present better growth rate than the other males. Then, tilapia seem to be very sensitive to the effects of social interactions. These social behaviour could strongly influence the growth differences between males and females

First paragraph: Breeding at a small size in tilapia diverts energy from growth into reproduction (territorial/courtship behavior and the metabolic cost of gamete production). Further, the progeny produced by the stocked fish compete for available space and food resources, thereby inhibiting the growth of the stocked fish, especially in ponds, where space and food quickly become limiting. Even in many parts of Southeast Asia where marketable size of tilapia is small (80-100 g), recruitment results in harvests that include 10-20% of small, larely unmarketable, fish. In African countries and urban areas in Asia where the premium market size for fresh fish is much larger, this figure can be as high as 50%.