Bait worms: a valuable and important fishery with implications for fisheries and conservation management

By Brenna Bales, SRC intern

Historically, bait fisheries around the world have been perceived as low-value, and their often limited, local extent makes large-scale management and conservation policy difficult to implement. Watson et. al 2016 explored three ragworm fisheries in the United Kingdom to investigate these claims, based on both evidence gathered scientifically and from an analysis of published literature. The data on polychaete bait fisheries is extremely limited, causing inaccurate estimates of catch amounts and collection efforts. In order to accurately assess the three bait fisheries of focus and other fisheries worldwide, Watson and other researchers assessed the following: retail value of bait species collected, extent of collection efforts both geographically and quantitatively, bait storage methods, and the choice and amount of bait used by angler fisherman on an average fishing trip.

The five most expensive (£/kg) species of marine animals sold on the global fish market are polychaetes (Glycera dibranciata, Diopatra aciculata, Nereis (Alitta) virens, Arenicola defodiens, and Marphysa sanguinea). The values of these bait species were quantified using retail prices of the species online and from data gathered from other literature sources. It was concluded that N. virens landings alone in the UK annually are worth approximately £52 million. Globally, this number is around £5.8 billion, with 121,000 tonnes of N. virens being landed worldwide. This demonstrates the high value of polychaete bait, contrary to popular opinion.

Nereis (Alitta) virens, commonly known as a sand worm, are a popular polychaete worm collected for bait purposes in UK tidal fisheries. (source:

Nereis (Alitta) virens, commonly known as a sand worm, are a popular polychaete worm collected for bait purposes in UK tidal fisheries. (source:

The three UK sites surveyed were Fareham Creek, Portsmouth Harbour; Dell Quay, Chichester Harbour; and Pagham Harbour. They were monitored over a period from August to September 2011, using remote closed circuit television recordings. The time for each digger on-site was recorded, and based on the number of times they placed a worm in their collection bucket, the biomass (mass of live worms) collected was estimated. The mean removal rate per bait collector per hour was 228 ± 64 worms. This large amount of collection can lead to things like environmental disturbance (trampling), over-exploitation of collection species, and the depletion of food resources for bird species that consume these worms.

This Japanese coastal bird feeds off a small ragworm, species that are globally collected as bait. When too many worms are removed by collectors, it can have serious consequences for the animals that rely on them for food. (source:

This Japanese coastal bird feeds off a small ragworm, species that are globally collected as bait. When too many worms are removed by collectors, it can have serious consequences for the animals that rely on them for food. (source:

An investigation as to how long certain species could be kept fresh before being used as bait on fishing trips was also conducted. The amount of time that N. virens could be maintained as viable bait was at the least 2 weeks. Given the average amount of N. virens used on angling trips per week was 0.33 kilograms, that amount of bait could be collected in only 28 minutes during a tidal cycle, based on the mean removal rate per bait collector per hour.

In conclusion, Watson et. al. proved that there needs to be a re-examination of the importance of polychaete bait fisheries worldwide, in order for better conservation initiatives to be launched. Seeing as the majority of these bait fisheries are located in MPAs (marine protected areas), better regulations must be enforced. There are several proposals in the study, such as personal catch limits, surveillance conservation, and stakeholder involvement. Overall, these fisheries are worth a lot more than is currently thought, and the implications of continuing poor management could have serious consequences.

Works Cited

Watson, Gordon J., et al. “Bait worms: a valuable and important fishery with implications for fisheries and conservation management.” Fish and Fisheries (2016).

Why do Fishers Fish?

By Emily Rose Nelson, SRC Graduate Student

Humans have been fishing for over 40,000 years. Initially, the world’s waters were thought of as a resource with no bounds. However, intensification of fishing pressure over the last 100 years has decimated fish populations, forcing us to realize that the oceans’ resources indeed do have limits. Today, fish make up more than 16 percent of the global human protein intake, whether it is in the form of subsistence fishing in developing countries or extravagant restaurants in wealthy countries. As demand for marine resources continues to grow, pressure on fish populations is also increasing. Governments around the world have started making efforts to slow the decline of ocean resources, but in many cases the success of these initiatives is dependent on compliance of the fishermen. Essentially, conservation efforts are in direct conflict with fisher objectives. For this reason, it is important to understand why a fisher is fishing in the first place – knowledge of fishers’ motivations will help policy makers identify the most effective conservation methods.

Young et al. 2016 set out to answer the question, “Why do fishers fish?” using an ethnographic approach. They conducted semi-structured interviews of experienced male fishermen at two sites, Australia and the Solomon Islands. The interviews gathered information about their general background, fishing methods, motivations for fishing, and feelings upon return from a fishing trip.

The interviews identified an overwhelming split in motivation to fish between the two study sites. 100 percent of fishers in the Solomon Islands were motivated by food and 93 percent were motivated by income. In contrast, 96 percent of the fishers in Australia were motivated by a connection to the environment. Recognizing these differences in incentives can help managers to form the best conservation policy for each region. For example, one could not realistically set in place a no-take marine reserve throughout the Solomon Islands without providing the fishermen and their families with an alternate source of food and income.

Motivations for fishing in Australia (gray bars) and the Solomon Islands (black lines).

Motivations for fishing in Australia (gray bars) and the Solomon Islands (black lines).

Despite the drastic difference in ‘primary reason to fish’ between the Solomon Islands and Australia, interviews revealed that many other drivers were the same. When fishers in the Solomon’s were given a hypothetical situation in which they had secured an alternate income, 100 percent of interviewees indicated that they would still continue to fish whenever possible. This shows that the fishers are getting enjoyment out of their work and indicates the presence of a somewhat recreational mindset. Therefore, if economic conditions were to improve in the area there would likely be a growth in recreational fishing. In Australia, where recreation is the primary reason for fishing, 80 percent of fishers identified food as a secondary incentive. For those people, fishing provides an escape from their stressful day to day lives, with the added bonus of catching a fresh meal for a price much cheaper than what is available at local fish markets.

Young et al. were not only able to identify clear-cut cultural differences in fishing motivations, but also recognize that fishing may provide benefits to individuals and communities that transcend these traditional motivations. In both the Solomon Islands and Australia, mentions of social bonds with fellow fishers and camaraderie were widespread in interviews. Lastly, the interviews revealed that fishing might not be as far off from conservation as some may think. The values identified of many fishers in this study, such as “teach children to appreciate nature” and “foster respect for the environment” are very similar to those of conservationists. As said by an Australian fisher, “fishing provides environmental benefits because we like to protect things that are dear to us.”


Young, A.L., Foale, S., & Bellwood, D.R. (2016) Why do fishers fish? A cross-cultural examination of the motivations for fishing. Marine Policy, 66: 114-123.

Why have global shark and ray landings declined: improved management or overfishing?

Paper by Lindsay N K Davidson, Meg A Krawchuk, Nicholas K Dulvy


By Pat Goebel, SRC Intern

A drop in shark and ray landings may be thought of as a success for in improved management strategies. However, in the case of Davidson et al (2015), that is too good to be true. Unfortunately, the decline in global shark and ray landings has been attributed to overfishing and other ecosystem influencers.

Sharks and rays are commercially valuable for their fins, meat, liver, oil and skin with their fins and meat. The demand for shark products is relatively new concept, as their commercial value has increased with the decline of other valuable fisheries. As on could assume with supply and demand, the high demand of shark products leads to an increase in fishing pressure. The increase in fishing pressure combined with the lack of laws regulating the shark and ray fishery, lead to the depletion of shark and ray populations. The rapid decline in shark and ray populations resulted in new management strategies. Davidson et al (2015), investigated these new management strategies to determine if declines in shark and ray catches were a result of the fisheries management performance or overfishing.

Figure 1 - Shark_fins_Taiwan

Shark and ray landings peaked in 2003 and have declined by about 20% in the past decade. Davidson et al. (2015), noted that the decrease is more likely related to overfishing than management implementations. The official harvest number used in this study is possibly two to three times below the actual number of sharks and rays being caught. This study highlights the fact that sharks and rays are being harvested at an unsustainable rate. Moreover, Davidson et al (2015), stressed several countries that warrant prioritization for conservation and management action. The greatest declines were reported in Pakistan and Sri Lanka, both of which have little to no management or enforcement. If new management strategies are not implemented into these countries, elasmobranch populations will continue to be harvest at a detrimental scale.

Figure 2. Global distribution of (a) country-specific shark and ray landings averaged between 2003 and 2011 and mapped as a percent of the total. (b) the difference between the averages of landings reported in 2001-2003 and 2009-2011

Figure 2. Global distribution of (a) country-specific shark and ray landings averaged between 2003 and 2011 and mapped as a percent of the total. (b) the difference between the averages of landings reported in 2001-2003 and 2009-2011


Masked, diluted and drowned out: how global seafood trade weakens signals from marine ecosystems

By Jake Jerome, RJD Graduate Student

It has been shown that global seafood trade inherently drives seafood production, negatively impacting marine ecosystems worldwide. While it is well known that these ecosystems are deteriorating, most research has been focused on global stock assessments, catch trends, or fisheries dynamics, with little attention given to researching the ways in which global trends are linked to consumers through trade. Fish prices can potentially be used as a feedback signal to consumers about the state of fisheries and marine ecosystems, but this method faces several issues. Crona et al 2015 dive deeper into the usefulness of using fish prices as a feedback signal, but develop a set of mechanisms that combine to weaken this signal from global trade to consumers.

The first mechanism that weakens price signals is masking. Masking occurs within individual fisheries and consists of two parts. First, negative impacts that arise from fishing are often separated from the operating cost of the fishery. For example, fisheries may cause habitat destruction or result in bycatch of endangered animals, but neither of these have a large impact on the yield or cost. Second, short-term catch trends may not provide accurate representation of target stock declines due to factors such as increased effort, technological advances, and fishing deeper or farther from shore.


Shrimp trawl net with bycatch (Elliott Norse, Marine Conservation Institute/Marine Photobank)

The second mechanism discussed is dilution. Dilution occurs when the amount of supply that an individual fishery has declines but is hidden from consumers by using the supply from another resource area. For example, the UK imports Atlantic cod from Iceland and Faeroes to make up for the decline of North Sea cod. Through dilution, changes in any one ecosystem are concealed from consumers because substitutable products are made available from different ecosystems.

A third mechanism examined is the ‘drowning out’ of price signals. This is usually due to other market factors that affect fish prices. Things like changes in consumer spending patterns or price/availability of alternative protein sources can combine to alter fish prices that do not necessarily connect with ecosystem or species decline.

Chilean Seabass for sale at Whole Foods (Gerick Bergsma 2011/Marine Photobank)

Chilean Seabass for sale at Whole Foods (Gerick Bergsma 2011/Marine Photobank)

In conclusion, the authors suggest that the feedback from individual fisheries to consumers worldwide is highly asymmetric and that price signals reflecting changes in the source ecosystem typically are masked, diluted, or drowned out unless large proportions of seafood stocks collapse. Despite this, opportunities do exist that possibly could help provide a positive feedback signal to consumers, resulting in promoting sustainable seafood practices.

Source: Crona, B. I., Daw, T. M., Swartz, W., Norström, A. V., Nyström, M., Thyresson, M., Folke, C., Hentati-Sundberg, J., Österblom, H., Deutsch, L. and Troell, M. (2015), Masked, diluted and drowned out: how global seafood trade weakens signals from marine ecosystems. Fish and Fisheries. doi: 10.1111/faf.12109

Evolution of Motherhood: The Importance of Mature Female Fish

By Daniela Ferraro, RJD Intern

Older, female fish are becoming a necessity for the continuation of trophy-fish hunting and sustainable commercial fishing. Looking at both freshwater and saltwater species, the presence of larger, more mature fish increases the productivity and stability of fish populations. Dr. Mark Hixon, of the University of Hawai’i at Manoa, refers to the loss of big fish as “size and age truncation.” Big, old, fat, fertile, female fish, affectionately nicknamed BOFFFFs, have proved the ability to produce significantly more eggs than younger fish. They also can spawn at different times and places, allowing them the option of evading potential predators and threats to their offspring. Efforts to protect older, larger fish include creation of marine reserves, which act as no-take zones. Marine reserves allow fish to spawn throughout their entire lives. As large fish, BOFFFFs are a valuable commodity in commercial fishing, as fisheries tend to target marketable commodities. This specified targeting alters a fishery’s modes and methods: through the narrowing of mesh size or gear type. Drift nets and long lines are used in the removal of larger fish from certain populations. To some extent, even bait type and hook affects the type of fish caught. Slot limits are placed on commercial fisheries, limiting them to catching only medium-sized fish. Although egg size variation among a single species may be narrow, across a diverse range, significant maternal effects have been noted in terms of larger egg size.

BOFFFFs: Big (1.1m), old (ca.100 years), fat (27.2 kg), fertile female fish: Shortraker rockfish (Sebastes borealis). Image Source: Karna McKinney, Alaska Fisheries Science Center, NOAA Fisheries Service

BOFFFFs: Big (1.1m), old (ca.100 years), fat (27.2 kg), fertile female fish: Shortraker rockfish (Sebastes borealis). Image Source: Karna McKinney, Alaska Fisheries Science Center, NOAA Fisheries Service

More mature females produce more, and often larger, eggs that typically develop into larvae that can withstand more intense challenges like starvation and have a faster growth rate. This is partly due to the physical body size, as a larger fish translates to a wider body cavity to allow for the development of larger ovaries. BOFFFFs have a tendency towards earlier and longer spawning seasons. With this flexibility, these fish can withhold spawning in unfavorable conditions. Once the danger of predation, or other threats, has passed, BOFFFFs can spawn abundantly and improve recruitment. Hixon refers to this phenomenon as the storage effect. This ability is preferential when considering commercial and differential fishing. The targeted removal of BOFFFFs results in a truncation of size and age structure of a specific population. The removal of older fish from an overfished population will increase their probability of species collapse. The assumption that younger female fish contribute equally to production and stock is detrimental to the future of sustainable fishery stocks.

Fishery productivity would find stability in the implementation of old-growth age structures. Berkeley suggested three methods to limit the overfishing of BOFFFFs: slot size limits with both minimums and maximums, low rates of fishing mortality, and marine reserves.  This can be accomplished with enforcement of both marine reserve no-take zones as well as catch limits. Marine reserves act not only as a direct safe place for fish to thrive and procreate, but also as a healthy influence on surrounding waters. They give maturing fish an area to develop, spawn and seed nearby fisheries.

Cape Rodney-Okakari Point, Goat Island Marine Reserve, New Zealand. Image Source: Wikimedia Commons

Cape Rodney-Okakari Point, Goat Island Marine Reserve, New Zealand. Image Source: Wikimedia Commons

Marine reserves act to provide ecosystems and environments for fish to not only reach sexual maturity, but past that. In addition, larvae from healthy marine reserves are found to seed the areas directly adjacent. This will assist in the replenishment of overfished and exploited populations. By integrating large-scale marine reserves, it is believed that it is possible to halt and reverse the decline of global fisheries while also protecting marine teleost, mammal, and invertebrate species. The decrease in mortality due to the protection of species by marine reserves and the subsequent increase in productivity has been seen in both temperate and tropical locations. Since marine reserves are located along reefs, estuaries, and kelp beds, it provides a large range in the protection of a diversity of species.

In a study conducted by Steven Berkeley et al, featuring 20 female black rockfish (Sebastes melanops), from five to seventeen years, it was found that larval groups from the older females grew three times faster than their counterparts. Larvae from the older fish also survived starvation twice as long. According to Berkeley, this is due to the provision of larvae with energy-rich triaglycerol (TAG) lipids as they increase in age. The TAG volume found in oil globules is positively correlated with age, growth rate, and survival. However, maternal effects can’t be classified as consistent across every species of teleost fish. Instead, research indicates that maternal effects have developed across a diverse taxonomic range. With the removal of matured female fish, populations are more likely to develop damaging consequences in terms of biodiversity and productivity.



Berkeley, Steven A., Mark A. Hixon, Ralph J. Larson, and Milton S. Love. “Fisheries Sustainability via Protection of Age Structure and Spatial Distribution of Fish Populations.” Fisheries 85.5: 23-32. Print.

Gell, Fiona R., and Callum M. Roberts. “Benefits beyond Boundaries: The Fishery Effects of Marine Reserves.” Trends in Ecology & Evolution 18.9: 448-55. Print.

Hixon, M. A., Johnson, D.W., and Sogard, S. M. BOFFFFs: on the importance of conserving old-growth age structure in fishery populations. – ICES Journal of Marine Science, 71: 2171–2185.

Towards more efficient longline fisheries: fish feeding behavior, bait characteristics and development.

By Sarah Hirth, RJD Intern

There has been a growing demand for bait resources seeing that standard bait types, such as squid, herring and mackerel are also used for human consumption. As a result, bait prices have increased, thus increasing the demand for an alternative bait, one that is not based on resources used for human consumption. This study highlights factors that need to be taken into consideration when looking for alternative bait, and explores attempts of alternative baits that have been made.

Løkkeborg at al. agree that an alternative bait should be “effective, species- and size-selective, practical for storage and baiting, and based on low-cost surplus products.” An alternative bait that would meet all of these characteristics would also make the procedure of longline fishing more environmentally friendly.

Although there have been several attempts to develop alternative baits, these have had limited success (e.g. Bjordal and Løkkeborg 1996; Januma et al. 2003; Polet al. 2008; Henriksen 2009). There have been two main methods, which have been used to create the alternative bait. These are natural resources, such as surplus products from the fishing industry and synthetic ingredients as attractants. Mentioned types of alternative bait are: Norbait, artificial bait invented by William E.S. Carr, bait bags, and arom bait.

Table 1

When these baits were tested, they all resulted in some positive factors. However, they still had undesirable outcomes. For example Norbait, which is based on surplus products, where minced fish products are mixed with alginate (a gelling agent, used as the binder) and extruded into a fiber mesh tube, has resulted in species –selective effects. In fishing trials Norbait has resulted in increased catch rates of two to three hundred per cent for haddock, yet Norbait compared poorly to natural bait for cod. “Compared to natural bait, minced herring enclosed in a nylon bag resulted in a 58% higher catch rates for haddock, a non-significant catch increase for tusk and ling, and a considerably lower catch rate for cod.” Similar results were observed with the other types of alternative baits.

The efficiency of longline baits depends on several factors, which are important to take into consideration when finding alternative baits. Some factors include: bait size, texture, and taste. An alternative bait also needs to be based on an odor source, and attractants need to be released over a considerable period of time. Løkkeborg et al. state that “the knowledge of food search behavior in fish is the basis of bait development efforts.” The list of factors affecting feeding behavior in this review includes: temperature, feeding motivation and hunger state, diel, tidal and annual rhythms, light levels, seasonal change in photoperiod, and water currents.

Figure 1

Although there currently are no alternative baits used in longline fishing, Løkkeborg et al. hope that improved knowledge of how fish respond to baited gear will aid future research aimed at the development of alternative baits. As the demand for marine resources for human consumption continues to increase, costs for longline bait are also likely to keep increasing. “The development of alternative baits used on resources not used for human consumption may therefore prove to be critical to a viable longline fisheries.”

Løkkeborg, S., et al. (2014). “Towards more efficient longline fisheries: fish feeding behaviour, bait characteristics and development of alternative baits.” Reviews in Fish Biology and Fisheries 24(4): 985-1003.