B.C.’s Herring Fishery
Irreplaceable source of omega-3
Report by
Johannes Roelofs, Prince Rupert B.C. April 1, 2019
The current controversy over potential closure of the Salish Sea herring roe fishery has to date failed to consider loss of irreplaceable omega-3 in the context of a global shortage with potential consequences for human life. It is a little-known fact that:
“Worldwide, 1.4 million deaths are attributable to diets low in seafood source omega-3 fatty acids. Fish consumption correlates with a 36 percent reduction in heart disease and heart attacks and a 12 percent reduction in mortality from all causes.” (Bennett et al.- 2018).
A shutdown of the Salish Sea herring fishery would therefore be expected to have serious potential negative consequences for human health and to increase global human mortality attributable to diets low in seafood source omega-3 fatty acids.
The problem with shutting down the Salish Sea herring fishery is that there is no alternative supply. There is a global shortage of omega-3 (EPA+DHA) amounting to 0.4 million tonnes1. This shortage is one third of the world’s annual omega-3 requirement to sustain human health. It is clear that shutting down the BC herring fishery will leave many more people without adequate omega-3.
The Salish Sea herring fishery in BC is generally acknowledged to have two components: the roe and the remainder (the portion of the fish once the roe has been stripped). Shutting down the fishery will eliminate the portion of the global supply of omega-3 (EPA+DHA) which these two components provide.
As of March 27th, the Salish Sea herring roe fishery had almost wound up for 2019 with a total harvest of 15,549 4 tonnes. This harvest contributes approximately the same amount of EPA+DHA to people’s diets as four million sockeye salmon contribute. We estimate it provides 36.5 million grams of EPA+DHA; enough to supply 400,000 people with an intake of ¼ gm/day/person2 for a
1 Tocher et al 2019 – “the available supply of [EPA+DHA] was insufficient to meet the demand to satisfy human requirements” – pg.1 “the supply of [EPA+DHA] can be optimistically estimated at just over 0.8 million tonnes indicating a shortfall of more than 0.4 million tonnes”-pg.3.
2 There are varying daily recommendations, many for more than ¼ gm. For example, Ikonomou et. al. 2007 (cited in footnote 17) suggest that values closer to 1/2 gram per day of Omega 3s may be more appropriate. We chose to use ¼ gm for our calculations because this was the value specifically associated with human mortality, not to recommend it .
(This estimate is based upon calculations set out in detail under the next heading).
Calculating the BC Salish Sea roe herring contribution of omega-3 to the human food supply
Herring Roe
We estimate the herring roe provides 15.5 million grams of EPA+DHA, enough to supply 170,000 people with an intake of ¼ gm/day/person2 for a year.
The roe from the Salish Sea fishery is 10 percent by weight, so of the total 15,549 tonne roe fishery, the roe therefore amounts to 1,555 tonnes (1.55 million kilograms) roe.
- Local scientists have tested the Salish Sea roe and found it contains 1% omega-3 (EPA+DHA) by weight which works out to 15.5 million grams of omega-3 (EPA+DHA) in the roe alone.
Herring Non-Roe remainder
We estimate there is 84 million grams of EPA+DHA in the non-roe remainder portion (herring carcasses stripped of roe which is processed into fish/animal feed), which, once fed to fish/animals and converted to food for people (assuming the 25% conversion rate described below and in footnote 7), provides 21 million grams of EPA+DHA enough to supply 230,000 people with an intake of ¼ gm/d/person for a year.
The total Salish Sea herring harvest is 15,549 tonnes 4 of which we estimate, 0.64% is omega-3
3 Huynh et al 2007 measured egg mass to be 29.95% of body weight (Table 1, p.506). However, in this report we are assuming a more conservative 20% for egg mass to body weight because 20% is the target for the commercial fishery on the grounds (“20% target rate” –
http://www.dfo-mpo.gc.ca/csas- sccs/Publications/SCR-RS/2019/2019_001-eng.pdf). We then further reduced the egg mass to body weight estimate to 10% to roughly account for the fact only the females have eggs.
4 “The roe herring gillnet fishery has not been active in recent days. Total estimated catch based n validations is 8,371 tons of the 11,472 ton quota.
The roe herring seine fishery closed March 15 at 16:00 hours with a total validated catch of 7,178 tons of the 8,311 ton quota.” – DFO Fishery Notice FN0291 March 27 2019.
5 Each gram of roe contains 2.81% total fat and that fat is 35.37% omega-3 (21.65% DHA and 13.72%EPA). – from Huynh et al 2007. From this we calculated the roe contains 1.1% omega-3 (DHA+EPA) byweight [2.81% times 35.37% = 1%].
We estimated the average amount of omega-3 in whole herring to be 0.64% by weight (0.71% formales and 0.57% for females) using a weighted average of the measurements given in Huynh et al
- Where they did not report measurements (for about 25% of the fish; including head, skin and tail) we estimated using the information from Aune et al 2003 that skin-off fillets of herring have about half the lipid levels of skin-on fillets. We assumed female fish are 20% roe (the fishery target) and the overall average lipid level for the skin, head and tail combined is 3%. We also assumed the DHA+EPA components of this lipid is the same as found in the skin-off fillet.
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(EPA+DHA). This works out to 99.5 million grams total EPA+DHA, of which, as noted above, 15.5 million grams is found in the roe portion leaving 84 million grams in the remainder which is processed into fish/animal feed.
When we feed this omega-3 rich fish/animal feed to farmed salmon or land-based livestock, a portion is used by the animal or salmon the feed is consumed by so only a portion of the EPA+DHA makes it to humans. The ratio of the amount of omega-3 in the feed (IN) to the amount remaining in the final product (OUT) is known as a conversion ratio. We estimated 21 million gm (of the total 84 million grams) EPA+DHA would end up reaching humans using a conversion rate of 25%7. 21 million grams is a year’s supply at ¼ gm/d for an additional 230,000 people.
Given the global deficit of omega-3, we strongly recommend that steps be taken to explore more efficient uses of scarce available omega-3. Direct consumption of the herring fillets rather than processing it into fish/animal feed would keep a significantly higher portion of the valuable and scarce omega-3 in the human food chain. As more people learn to enjoy not just the roe but the herring fillet, we can increase the utilization of the omega-3 value of the harvest. One way to do this is already being tried and involves joining the commercial fishermen and others who are working to build awareness at annual public herring sales. These relatively small but exciting local events provide the whole nutritious fish to be eaten directly by people. Sixty tonnes of whole herring were sold to the public in just six hours at one annual BC herring sale8. While we strongly endorse such attempts to utilize more of the valuable and scarce omega-3 in this more direct manner, we acknowledge that it takes time to change people’s traditions and tastes and, in the meantime, the existing roe herring fishery is providing a very large benefit, albeit not as large a benefit as it otherwise could.
7 The IN:OUT conversion ratio is 4:1 [0.122 to 0.03] or 25%. We arrived at that 25% conversion ratio by locating an estimate of the total amount of omega 3 (EPA + DHA) used in salmonid production world-wide (Toppe 2010). We then compared that to the total amount of EPA+ DHA remaining in the product of global salmonid production. We did this by multiplying the total production by the current EPA+DHA % in farmed salmon.
For the omega 3 EPA+DHA input (Toppe 2010) indicates that: IN = 0.122 million tonnes (MT) EPA+DHA.
122,000 tonnes of EPA+DHA is used for salmon and trout production (Toppe (2010). This amount appears to have remained relatively stable over the years. For the Omega 3 EPA+DHA output: OUT = 0.03 MT EPA+DHA Production of salmonids was 3.052 MT in 2016 (FAO 2018) and 3.63 MT in 2018 if we assume a 9% growth rate (8-10 % for aquaculture sector-Tacon et al 2011). The amount of EPA+DHA in farmed
salmon has declined steadily from 2.7 g/100 g fish in 2006 to 1.4 g/100 g in 2015 (Sprague et al. (2016) Supplementary Table 1). A recent analysis of farmed salmon (Crowley and Gormley (2018) p.8, Table 8) reports EPA+DHA content as between 0.77 g/100 g (Ireland) to 0.86 g/100 g (Scotland). If we use 0.83 g/100g (Norway, the largest producer has 0.81 g/100g) as representative then the 3.63 million tonnes of salmonid production conveyed 0.03 MT of EPA+DHA to the marketplace in 2018.
https://www.richmond-news.com/news/herring-sale-a-hit-for-cancer-kids-1.2129584
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Four Million Sockeye
To provide a comparison that would be familiar to most British Columbians who tend to associate omega- 3 with salmon, we estimate it would take 4.2 million sockeye to provide the same amount of omega-3 that the Salish Sea herring fishery does.
As set out above, the Salish Sea Herring supplies 36.5 million grams EPA+DHA (15.5 from the roe and from fish/animals, most likely salmon, fed the remainder herring).
In order to make the comparison between the omega-3 value of the herring fishery and the more familiar salmon, we calculated the number of sockeye salmon it would take to provide the same 36.5 million grams omega-3 (EPA +DHA). 4.20 million sockeye weighing 2.495 kg/sockeye9 is 10.5 million kg of sockeye, which, with a recovery of 50%10 into the edible portion leaves 5.25 million kg of sockeye. Sockeye fillets contain 0.7% 11 omega-3 (EPA+DHA) in the edible portion. [5.25 million kg X .007 (EPA+DHA) X 1000 gm/kg = 36.5 million grams].
Irreplaceable health benefits provided by BCs herring fishery
The type and form of omega-3 oil provided by the Salish Sea herring fishery is essential to human health and is in short supply:
“EPA and DHA are well accepted as being essential components of a healthy, balanced diet, having beneficial effects on development especially of the neural system, and in mitigating a number of pathological conditions. However, what is not so well known or appreciated is that these nutrients are in short supply”12 13
It may be suggested that the omega-3 now provided by the Salish Sea herring fishery could be replaced with flax oil or other land or plant-based sources of omega-3. This is not possible because the beneficial types of omega-3 found in plants (ALA and DPA) are different from fish derived omega-3 which has EPA and DHA and it is this fish derived omega-3 (EPA+DHA) which is in short supply globally and which is associated with a myriad of unique human health benefits.
“the limitation in availability of EPA and DHA is linked to their aquatic, predominantly
Poetter & Shriver 2018 report the average Bristol bay sockeye salmon weight as 5.5 pounds (2.495kg).
10 Conversion rates for sockeye are: Skin-On Fillet = 57%, Skinless Fillet = 50% and Skinless, Boneless fillet = 38% – Office of Fisheries Development Seafood Processing Recovery Rates
11 USDA Nutrient Data Base – sockeye salmon raw 0.722/100 gm EPA and DHA.
12 Omega-3 Long-Chain Polyunsaturated Fatty Acids, EPA and DHA: Bridging the Gap between Supply and
Demand-Tocher et al 2019.
13 A summary of the evidence regarding the essential nature of EPA+DHA is given under the heading
“The Evidence Base -FAO/WHO 2014 page 7.
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marine origin…the vast majority is produced at the base of the marine food web …, whereas
terrestrial plants do not produce EPA or DHA. Consequently, our supplies of [omega-3 EPA and DHA]
come from the oceans… Therefore, while other animal-derived foods can contribute small amounts of [omega-3 EPA+DHA], access to, and consumption of, fish and seafood is the major factor” 14 15
The evidence for the health benefits of EPA and DHA types of omega-3 is extensive and well accepted.16 The recommended intake of omega-3 (EPA+DHA) by the American Heart Association, World Health Organization, European Food Safety Authority and many other agencies, for cardio- protective effects in adults without coronary heart disease (CHD), is ½ gm daily17. Other potential positive effects of eating omega-3 include benefits for dementia, depression, asthma, diabetes, possibly life expectancy (increased telemere length) and reduction in general cardiovascular risk. There is mounting evidence that eating as little as ¼ gm per day of omega-3 has many general health benefits: decrease in depression, as brain food, that is, enhancement of cognitive and visual
abilities, prevention of cancer and even, improved love life. It’s also important for nursing
mothers and for neural development during infancy.
There already is a huge (about one third- as described above) global shortfall in the supply of essential omega-3 needed to meet the recommended levels for human health.18 Closing the BC Salish Sea herring fishery will only exacerbate this situation with an anticipated associated rise in the number of global human deaths attributable to diets low in seafood source omega 3 fatty acids.
We note that an independent review of the Department of Fisheries Salish Sea herring stock assessment found that: “fishery monitoring data shows that spawning biomass is at a historic high…”
- page 9 Canadian Science Advisory Secretariat
A truly sustainable environmental approach to resource management would take into account the fisheries’ food and nutrition benefits and the expected consequences of loss of these important sources of nutrients for humans as well as ensuring that the resource remains healthy.
14 Tocher et al 2019
15 The same point is made in “Terrestrial meats (beef, pork, mutton and poultry), particularly from grass-fed livestock, can contribute significant amounts of n-3 PUFAs, primarily in the form of ALA and decosapentaenoic acid (DPA). However, oils found naturally in fish are the richest dietary sources of EPA and DHA. “-FAO/WHO 2014
16 FAO/WHO (2014) – See “The Evidence Base” page 7 [note: There is concern that processing omega-3 into supplements may limit its benefits but the Salish Sea herring fishery benefits are from omega-3 eaten directly in the form of roe, not supplements.]
17 Ikonomou et al. -2007
18 Tocher et al 2019
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Human lives: The cost of shutting down the fishery?
The Salish Sea fishery provides enough EPA+DHA to give ¼ gm/d for a year to 400,000 people19.
Mozaffarian and Rimm reported that an average daily intake of ¼ gm of EPA+DHA over a 70-year lifetime would result in 7,125 fewer CHD deaths per 100,000 individuals.20
A recent meta-study found a similarly large benefit;
“Dose-response analysis suggested that the risk of all-cause mortality was reduced by 7% for every 0.2 g per day increment in [EPA+DHA] consumption.”- Wan et al. 2017
We calculate from this finding by Wan et al that an average daily ¼ gm intake of EPA+DHA over a 70-year lifetime would result in 7,656 fewer deaths21 from all causes per 100,000 individuals. 7,656 fewer deaths per 100,000 individuals would be 30,624 fewer deaths per 400,000 individuals
(over a 70-year lifetime). 400,000 is the number of individuals who could be supplied with a ¼ g/d by the annual Salish sea herring fishery omega-3 source).
Knowing that we already have a significant number (1.4 million per Bennet et al 2018) of human deaths attributable to diets low in seafood source omega-3, loss of additional omega-3 to this large number of persons can only serve to significantly exacerbate the number of worldwide deaths.
References
Aune, M., Bjerselius, R., Atuma, S., Darnerud, P. O., Andersson, A., Arrhenius, F., Bergek, S., Tysklind, M., and Glynn, A. (2003). Large differences in dioxin and pcb levels in herring and salmon depending on tissue analysed. Organohalogen compounds, 64:378–81.
Bennett, A., Patil, P., Kleisner, K., Rader, D., Virdin, J., and Basurto, X. (2018). Contribution
of fisheries to food and nutrition security: current knowledge, policy, and research. Nicholas Institute
19 See Calculations- page 2 Herring Roe (170,000) and Herring Remainder (230,000)
20 Mozaffarian and Rimm 2006 JAMA October 18, 2006—Vol 296, No. 15 pages 1893-1894
21 Longevity in Canada is about 80 years; the average risk of all cause-mortality is 1/80 or 0.0125/year. 87,500 out of 100,000 people will die over a 70-year period [0.0125* 100,00070]. Providing .2 gm/d EPA+DHA results in a 7% risk reduction (Wan). Given a linear dose response relationship we calculate the risk reduction for .25 gm/d to be 8.75%. The new risk of all-cause mortality (with ¼ gm/d EPA+DHA) will be 0.01140625/year at which rate 79,844 out of 100,000 people will die over a 70-year period. This is 7656 fewer deaths over a 70-year period. [100,00070*
(.0125 -.01140625) = 7656]
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http://www.adfg.alaska.gov/FedAidPDFs/SP18-08.pdf
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