Ray Hilborn Says Recent Science Paper Makes Inflated Claim about Human Impacts on Marine Species
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Ray says the authors made a mistake in only looking at individual predators and in not considering all predation on a given species. He says that when all predation is considered, the results reverse themselves, and that natural predators take a larger proportion of adult marine fish than humans do.His comment is below:Comment by Ray Hilborn, University of WashingtonThis paper claims that humans have a up to 14 times higher exploitation rate than natural predators. There is a basic flaw in the analysis which diminishes the validity of the conclusions the authors come to. First the calculated predation rate of natural predators will depend on how many predators you look at. Dozens or even hundreds of species may prey upon a given species, most of them taking a trivial fraction of the prey. If you find data only for the most important predators (the ones that take the most of the prey species) you will estimate a high predation rate, but if you find data for all the species that prey upon a species the median will be much much lower.In fact there are hundreds of potential predators for any species, most take none of the prey species, so if you had data for all of them you would say that the average predation rate was nearly zero for natural predators. Thus the more data on predation rate for individual species you can find, and the more you find predation data for trivial predators, the lower you will estimate “average” predation. However, if you look at the predators who take the most of the specific prey the fraction of the prey will be much higher and often more than humans.
The more important question is what is the total predation rate compared to the human exploitation rate? One has to read the Darimont paper carefully to realize they are talking about rates of individual predatory species, not rates of predators as a whole. For instance their abstract says “humans kill adult prey… at much higher median rates than other predators (up to 14 times higher). ” Thus they are comparing the rates of all other predatory species taken one at a time to that of humans. There may be natural predators who have a very high predation rate (higher than humans), but they are masked by the average of other predators with low rates. The clear implication is that we take more adults than do predators. Much of the media coverage interprets their results this way.This is absolutely not true as shown in the analysis below which shows that humans take about ½ as many adult fish as marine predators.
Chart: Ray HilbornTo compare the rates of fishing mortality to rates of natural mortality (almost all of which is from predation), I used the RAM Legacy Stock Assessment Data Base (www.ramlegacy.org) the same data base used by Dairmont et al. to obtain fishing mortality rates. I selected the 223 fish stocks for which we had both natural mortality and human exploitation rates, and plot the distribution of the two in the graph below. We find that fishing mortality on adult fish is on average roughly ½ of the predation rate --- not 14 times higher as the abstract of their paper would leave you to believe. Remember Dairmont were not looking at all of predation, but counting each predator as an individual data point. In aggregate predators take far more adult fish than do humans, but you would not understand that by reading the Dairmont paper.The authors conclude that argument that globally humans are unsustainable predators. This flies in the face of the fact that we have considerable empirical evidence that we can sustainably harvest fish and wildlife populations. The basic key to sustainable harvesting is keeping the fraction exploited at a level that can be sustained in the long term, and adjusting harvest up and down as populations fluctuate. The Food and Agriculture Organization of the United Nations provides the most comprehensive analysis of the status of global fisheries and estimates than about 30% of global fish stocks are overexploited – the other 70% are at levels of abundance that are generally considered sustainable.Many fisheries are evaluated by independent organizations like the Marine Stewardship Council and Monterey Bay Aquarium and classified as “sustainable” yet Dairmont and co-authors suggest that no fisheries are sustainably managed.As an example, sockeye salmon in Bristol Bay Alaska have been sustainably managed for over a century, have been evaluated as sustainable by every independent organization, and the key is limiting harvest so that enough fish reach the spawning grounds to replenish the species. In this case humans take about 2/3 of the returning adult salmon – a much higher fraction than the predators, but it is sustainable and stocks are at record abundance.Darimont and coauthors suggest we need to reduce exploitation pressure by as much as 10 fold. This may be true in some places but in the US we manage fisheries quite successfully. We agree with the authors that management is key to keeping healthy and sustainable populations of fish and wildlife. However, instead of “emulating natural predators” and decreasing human exploitation across the board, we need to work to use our knowledge to expand good management practices to more species and areas of the world.
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Letters: Grossman Article on Reasons for Sardine Decline Inaccurate
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SEAFOODNEWS.COM [Letters] - June 23, 2015Editor’s Note: The following letter from D.B. Pleschner was reviewed and supported by Mike Okoniewski of Pacific Seafoods.To the Editor: I take exception to your statement: "The author of this piece, Elizabeth Grossman, buys into the argument, but in a fair article.”In no way was this “fair” reporting. She selectively quotes (essentially misquotes) both Mike Okoniewski and me (and this after I spent more than an hour with her on the phone, and shared with her the statements of Ray Hilborn, assessment author Kevin Hill and other noted scientists.) She does not balance the article but rather fails to emphasize the NOAA best science in favor of the Demer-Zwolinski paper, published in NAS by NOAA scientists who did not follow protocol for internal review before submitting to NAS (which would have caught many misstatements before they saw print).NOAA’s Alec MacCall later printed a clarification (in essence a rebuttal) in NAS, which pointed out the errors and stated that the conclusions in the Demer paper were “one man’s opinion”.Oceana especially has widely touted that paper, notwithstanding the fact that the SWFSC Center Director also needed to testify before the PFMC twice, stating that the paper’s findings did not represent NOAA’s scientific thinking.After the Oceana brouhaha following the sardine fishery closure, NOAA Assistant Administrator Eileen Sobeck issued a statement. SWFSC Director Cisco Werner wrote to us in response to our request to submit Eileen’s statement to the Yale and Food & Environment Reporting Network to set the record straight:“The statement from the NMFS Assistant Administrator (Eileen Sobeck) was clear about what the agency's best science has put forward regarding the decline in the Pacific Sardine population. Namely, without continued successful recruitment, the population of any spp. will decline - irrespective of imposed management strategies.”It is also important to note that we are working closely with the SWFSC and have worked collaboratively whenever possible.I would greatly appreciate it if you would again post Sobeck’s statement to counter the inaccurate implications and misstatements in Elizabeth Grossman’s piece.Diane Pleschner-SteeleCalifornia Wet Fish Producers AssociationPS: I also informed Elizabeth Grossman when we talked that our coastal waters are now teeming with both sardines and anchovy, which the scientific surveys have been unable to document because the research ships survey offshore and the fish are inshore.Sobeck’s statement follows:Researchers, Managers, and Industry Saw This Coming: Boom-Bust Cycle Is Not a New Scenario for Pacific SardinesA Message from Eileen Sobeck, Head of NOAA FisheriesApri 23, 2015Pacific sardines have a long and storied history in the United States. These pint-size powerhouses of the ocean have been -- on and off -- one of our most abundant fisheries. They support the larger ecosystem as a food source for other marine creatures, and they support a valuable commercial fishery.When conditions are good, this small, highly productive species multiplies quickly. It can also decline sharply at other times, even in the absence of fishing. So it is known for wide swings in its population.Recently, NOAA Fisheries and the Pacific Fishery Management Council received scientific information as a part of the ongoing study and annual assessment of this species. This information showed the sardine population had continued to decline.It was not a surprise. Scientists, the Council, NOAA, and the industry were all aware of the downward trend over the past several years and have been following it carefully. Last week, the Council urged us to close the directed fishery on sardines for the 2015 fishing season. NOAA Fisheries is also closing the fishery now for the remainder of the current fishing season to ensure the quota is not exceeded.While these closures affect the fishing community, they also provide an example of our effective, dynamic fishery management process in action. Sardine fisheries management is designed around the natural variability of the species and its role in the ecosystem as forage for other species. It is driven by science and data, and catch levels are set far below levels needed to prevent overfishing.In addition, a precautionary measure is built into sardine management to stop directed fishing when the population falls below 150,000 metric tons. The 2015 stock assessment resulted in a population estimate of 97,000 metric tons, below the fishing cutoff, thereby triggering the Council action.The sardine population is presently not overfished and overfishing is not occurring. However, the continued lack of recruitment of young fish into the stock in the past few years would have decreased the population, even without fishing pressure. So, these closures were a “controlled landing”. We saw where this stock was heading several years ago and everyone was monitoring the situation closely.This decline is a part of the natural cycle in the marine environment. And if there is a new piece to this puzzle -- such as climate change -- we will continue to work closely with our partners in the scientific and management communities, the industry, and fishermen to address it. Read/Download Elizabeth Grossman's article: Some Scientists and NGO’s Argue West Coast Sardine Closure was too Late
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Ray Hilborn Asks If the Drive for MPA's is Environmentally Shortsighted
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SEAFOODNEWS.COM [SeafoodNews] April 29 2015
Researchers, Managers, and Industry Saw This Coming: Boom-Bust Cycle Is Not a New Scenario for Pacific Sardines
A Message from Eileen Sobeck, Head of NOAA FisheriesPacific sardines have a long and storied history in the United States. These pint-size powerhouses of the ocean have been -- on and off -- one of our most abundant fisheries. They support the larger ecosystem as a food source for other marine creatures, and they support a valuable commercial fishery. When conditions are good, this small, highly productive species multiplies quickly. It can also decline sharply at other times, even in the absence of fishing. So it is known for wide swings in its population.Recently, NOAA Fisheries and the Pacific Fishery Management Council received scientific information as a part of the ongoing study and annual assessment of this species. This information showed the sardine population had continued to decline. It was not a surprise. Scientists, the Council, NOAA, and the industry were all aware of the downward trend over the past several years and have been following it carefully. Last week, the Council urged us to close the directed fishery on sardines for the 2015 fishing season. NOAA Fisheries is also closing the fishery now for the remainder of the current fishing season to ensure the quota is not exceeded.While these closures affect the fishing community, they also provide an example of our effective, dynamic fishery management process in action. Sardine fisheries management is designed around the natural variability of the species and its role in the ecosystem as forage for other species. It is driven by science and data, and catch levels are set far below levels needed to prevent overfishing. In addition, a precautionary measure is built into sardine management to stop directed fishing when the population falls below 150,000 metric tons. The 2015 stock assessment resulted in a population estimate of 97,000 metric tons, below the fishing cutoff, thereby triggering the Council action.The sardine population is presently not overfished and overfishing is not occurring. However, the continued lack of recruitment of young fish into the stock in the past few years would have decreased the population, even without fishing pressure. So, these closures were a “controlled landing”. We saw where this stock was heading several years ago and everyone was monitoring the situation closely.This decline is a part of the natural cycle in the marine environment. And if there is a new piece to this puzzle -- such as climate change -- we will continue to work closely with our partners in the scientific and management communities, the industry, and fishermen to address it.To learn more about this amazing fish, go to these websites:FishWatchNOAA Southwest Fishery Science CenterNOAA Fisheries West Coast RegionPacific Fishery Management Council
Read the original post: www.nmfs.noaa.gov
Another View: Sardine population isn’t crashing
Freshly caught sardines awaiting sorting at West Bay Marketing in Astoria, Ore. On April 15, federal regulators approved an early closure of commercial sardine fishing off Oregon, Washington and California to prevent overfishing. Alex Pajunas Associated Press file
By D.B. Pleschner | Special to The BeeEnvironmental groups such as Oceana complain that the sardine population is collapsing just as it did in the mid-1940s. They blame “overfishing” as the reason and maintain that the fishery should be shut down completely (“Starving sea lions spotlight overfishing,” Viewpoints, April 14).In truth, Pacific sardines are perhaps the best-managed fishery in the world. The current rule – established in 2000 and updated last year with more accurate science – sets a strict harvest guideline. If the water temperature is cold, the harvest rate is low. And if the population size decreases, both the harvest rate and the allowable catch automatically decrease.It’s inaccurate and disingenuous to compare today’s fishery management with the historic sardine fishery collapse that devastated Monterey’s Cannery Row. During the 1940s and ’50s, the fishery harvest averaged more than 43 percent of the standing sardine stock. Plus, there was little regulatory oversight and no limit on the annual catch.Since the return of federal management in 2000, the harvest rate has averaged about 11 percent, ranging as low as 6 percent. Scientists recognize two sardine stocks on the West Coast: the northern stock ranges from northern Baja California to Canada during warm-water oceanic cycles and retracts during cold-water cycles. A southern or “temperate” stock ranges from southern Baja to San Pedro in Southern California. The federal Pacific Fishery Management Council manages only the northern stock.Doing the math, our current fishery harvest is less than a quarter of the rate during the historical sardine collapse. The so-called “sardine crash due to overfishing” mantra now peddled by Oceana isn’t anything of the sort. It’s simply natural fluctuations that follow the changing conditions of the ocean, reflected in part by water temperature.California’s wetfish industry relies on a complex of coastal species including mackerel, anchovy and squid, as well as sardines. Sardines typically school with all these species, so a small allowance of sardine caught incidentally in these other fisheries will be necessary to keep wetfish boats fishing and processors’ doors open.Sardines are critically important to California’s historic wetfish industry. This industry produces on average 80 percent of total fishery catches, and close to 40 percent of dockside value. A total prohibition on sardine harvests could curtail the wetfish industry and seriously harm California’s fishing economy.
Read the original post: www.sacbee.com
D.B. Pleschner: Sardines are not being overfished
In recent weeks, sardines have been a hot news topic again. Environmental groups like Oceana complain that the sardine population is collapsing just like it did in the mid-1940s. They blame “overfishing” as the reason and maintain that the fishery should be shut down completely.Today, in truth, Pacific sardines are perhaps the best-managed fishery in the world — the poster fish for effective ecosystem-based management. The current harvest control rule — established in 2000 and updated last year with more accurate science — sets a strict harvest guideline that considers ocean conditions and automatically reduces the catch limit as the biomass declines.If the temperature is cold — which hampers sardine recruitment — the harvest rate is low. And if the population size decreases, both the harvest rate and the allowable catch automatically decrease.Current management sets aside a 150,000 metric ton reserve off the top of the stock assessment and automatically closes the directed fishery when the biomass estimate falls below that level, which it did in the latest stock assessment, after four years of abnormally cold La Niña ocean conditions.In fact, the truth is much more complicated than environmentalists would lead you to believe. It’s inaccurate and disingenuous to compare today’s fishery management with the historic sardine fishery collapse that devastated Monterey’s Cannery Row.In the 1940s and ‘50s, the fishery harvest averaged more than 43 percent of the standing sardine stock. Plus, there was little regulatory oversight and no limit on the annual catch.Today, based on the latest stock assessment, the U.S. exploitation rate has averaged about 11 percent, ranging as low as 6 percent, since the return of federal management in 2000.Here’s where complications begin because scientists recognize two stocks on the West Coast: the northern or “cold” stock ranges from northern Baja California to Canada during warm-water oceanic cycles and retracts during cold-water cycles.A southern or “temperate” stock ranges from southern Baja to San Pedro, in Southern California. The federal Pacific Fishery Management Council manages only the northern stock.Doing the math, our current fishery harvest is less than one-quarter of the rate observed during the historical sardine collapse.In fact, the current sardine harvest rule is actually more precautionary than the original rule it replaced. It does this by producing an average long-term population size at 75 percent of the unfished size, leaving even more fish in the water, vs. 67 percent in the original rule. The original harvest rule reduced the minimum harvest rate to 5 percent during cold periods. The present has a minimum rate of 0 percent during cold periods.The so-called “sardine crash due to overfishing” mantra now peddled by Oceana isn’t anything of the sort. It’s simply natural fluctuations in biomass that follow the changing conditions of the ocean, reflected in part by sea temperature.In April, the council will discuss the most recent sardine assessment report and decide on future management measures. It is important to understand that the sardine stock assessment is a conservative estimate based on acoustic surveys that miss sardines in the upper 10 meters of the water column, above the down-looking acoustic transducer, and in shallow near-shore waters where survey vessels cannot go. It’s really a question of scale, fishermen say. While they acknowledge sardines’ downward trend, fishermen question the accuracy of the total number of sardines that the stock assessment estimates.California’s wetfish industry relies on a complex of coastal pelagic species including mackerels, anchovy and market squid as well as sardines. Sardines typically school with all these species, so a small allowance of sardine caught incidentally in these other fisheries will be necessary to keep wetfish boats fishing and processors’ doors open.Sardines are critically important to California’s historic wetfish industry as well as the Golden State. This industry produces on average 80 percent of total fishery landings, and close to 40 percent of dockside value. A total prohibition on sardine landings could curtail the wetfish industry and seriously harm California’s fishing economy.D.B. Pleschner is executive director of the California Wetfish Producers Association, a nonprofit dedicated to research and to promote sustainable wetfish resources.
Posted in http://www.montereyherald.com 04/04/15
Comment to Pacific Fishery Management Council
INFORMATION COMPILED BY DR. RICHARD PARRISH
“The reason that the sardine population has declined so rapidly in the last few years is exceedingly simple. The story is easily seen in the figures I have attached here.
There was a very poor year-class in 2010 followed by 3 years of total recruitment failure. Both the sardine stock assessment and the Acoustic-Trawl series clearly show this. End of story.The sardine control rule did exactly what it was designed to do. It has shut down the directed fishery after a series of poor recruitment years. — Richard ParrishSardine recruitment in billions of one-year-old fish; 2010 was a very poor reproductive year and it was followed by three years of complete reproductive failure (2011, 12, 13). The estimate for 2014 is a statistical forecast based on the average recruits per spawner. Few 2014 sardines have been observed. (Hill et al 2015 Sardine Stock Assessment)
The spawning stock biomass fell from about 600,000 mt in 2010 to a bit over 100,000 mt in 2015. With no recruitment, biomass drops very fast with or without a fishery. The same thing happened in the Japanese Sardine fishery about 20 years ago.
Here is the Acoustic survey data showing again the complete reproductive failure in the 2011-13 year classes.
Sea Lion pups are starving in Southern California and Oceana claims it is due to overfishing of sardine. Here are the food habits of sardine. They are 8th in abundance in the California sea lion diet.
Lowry, M. S. and J. V. Carretta. 1999. Market squid (Loligo opalescens) in the diet of California sea lions (Zalophus californianus) in southern California (1981-1995). CalCOFI Rep. 40:196-207.
Here is the time series of sea lion pups. This is used as the primary population index. The most recent total estimate is as follows: (from CALIFORNIA SEA LION (Zalophus californianus ): U.S. Stock. Revised 12/15/2011)POPULATION SIZEThe entire population cannot be counted because all age and sex classes are not ashore at the same time. In lieu of counting all sea lions, pups are counted during the breeding season (because this is the only age class that is ashore in its entirety), and the number of births is estimated from the pup count. The size of the population is then estimated from the number of births and the proportion of pups in the population. Censuses are conducted in July after all pups have been born. To estimate the number of pups born, the pup count for rookeries in southern California in 2008 (59,774) was adjusted for an estimated 15% pre-census mortality (Boveng 1988; Lowry et al. 1992), giving an estimated 68,740 live births in the population. The fraction of newborn pups in the population (23.2%) was estimated from a life table derived for the northern fur seal (Callorhinus ursinus) (Boveng 1988, Lowry et al. 1992) which was modified to account for the growth rate of this California sea lion population (5.4% yr-1, see below). Multiplying the number of pups born by the inverse of this fraction (4.317) results in a population estimate of 296,750.Minimum Population EstimateThe minimum population size was determined from counts of all age and sex classes that were ashore at all the major rookeries and haul-out sites in southern and central California during the 2007 breeding season. The minimum population size of the U.S. stock is 153,337 (NMFS unpubl. data). It includes all California sea lions counted during the July 2007 census at the Channel Islands in southern California and at haul-out sites located between Point Conception and Point Reyes, California. An additional unknown number of California sea lions are at sea or hauled out at locations that were not censused.Current Population TrendTrends in pup counts from 1975 through 2008 are shown in Figure 2
INFORMATION COMPILED BY CWPA
ALLOWING AN ADEQUATE INCIDENTAL SARDINE CATCH IN OTHER CPS FISHERIES IS CRITICAL TO SUSTAIN CALIFORNIA’S WETFISH INDUSTRY
