Thursday, February 25, 2016

Harvesting and the Spherical Cow: From Zebrafish to Menhaden to Red Snapper, by Don Orth

Regulating harvest is perhaps the most fundamental role for fisheries management.  The theory is far easier than the practice.  Developers of early fisheries theory (Beverton and Holt 1957) invoked the “spherical cow” in fisheries.  The spherical cow is a metaphor for mathematically describing the problem in the simplest form possible to make calculations more feasible. As we see with stories about the Zebrafish (Danio rerio), Atlantic Menhaden (Brevoortia tyrannus), and Red Snapper (Lutjanus campechanus), the simplification hinders application.  

Zebrafish female top, male bottom.  Photo by
Zebrafish is member of the minnow family (Cyprinidae); it is native to the southeastern Himalayan region.  Zebrafish readily adapt to life in aquaria and they have a fast development time and short generation time; for these reasons they have become a model fish for laboratory investigations, typically development, gene function, and toxicology.

Atlantic Menhaden is a member of the herring family (Clupeidae); it lives in estuaries and coastal waters from Nova Scotia to northern Florida.  They are filter feeders that swim with their mouth open and gill openings spread.  They travel in large schools and are preyed upon by many fish, marine mammals, and birds,  Atlantic Menhaden mature in two years at a size of 18-22 cm; females produce between 100,000 to 600,000 eggs, depending on size.  Common names include the pogy, mossbunker, bunker, fat-back, and bug-mouth.  Native Americans called them 'munnawhatteaug' (=fertilizer).
Atlantic Menhaden
Red Snapper is a long-lived, early-maturing fish in the family Lutjanidae.  They are broadly distributed in the Gulf of Mexico and are an important sport and commercial fish.  Red Snapper have been overfished for several decades and are one of the most controversial fisheries with high landings from both recreational and commercial fishers.
Red Snapper caught in January 2013 was 38.25 inches and was released due to closed season.
Any valuable fish will be intensely targeted by both commercial and recreational anglers.   Intense fishing pressure will remove the large and mature members of the populations.  Consequently, truncated age distributions and artificial selection are pervasive fisheries problems.  The first response of managers is to enact a minimum length for possession that allows at least one successful reproduction before first harvest.  Yet this management approach facilitates higher harvest on larger fish, often leading to recruitment overfishing and lack of large fish.   Instead of more and bigger fish, the fishing public is left with fewer and smaller fish.  

This gradual decline in the average size of fishes caught in intensely harvested populations has been documented in numerous fisheries (Silliman 1975; Ricker 1981; Sharpe and Hendry 2009; Arlinghaus et al. 2010).  Cautious managers warned that intensive size selective fishing could lower fisheries productivity over time (Hutchings 2009; Rijnsdorp et al. 2010; Heino et al. 2013).  The effects of size selective fishing are not only plausible, but potentially widespread.   
The mathematics of optimum size based harvesting (Reed 1980) is based on the assumptions of stationarity and identical fish in each age group.  The population is further assumed to interact with no others (as predator or prey or competitor).  The maximization of yields based on Reed’s mathematical model demonstrated that under intense levels of exploitation, harvesting restricted to two age groups maximizes yields.  The mathematical theorem does not support the application of minimum size limits as an optimal strategy.  Rather, the optimal size to harvest depends on exploitation rate.   And old, more fecund age groups, are protected from harvest.
Annual steady state yield expected at different levels of exploitation.  The numbers on line segments represent the minimum age of first harvest (A), or the range of ages harvested (C). Curve B represents no minimum age limit (Reed 1980).
Uusi-Heikilla and others (2015) recently explored the effects of intensive harvest on Zebrafish populations to address the controversy of whether harvesting causes genetic as opposed to mere phenotypic changes.  The question is critically important to fisheries manager as genetic changes are more slowly reversible.  The use of Zebrafish allowed the investigators to follow populations over 5 generations of intense size selective pressure and examine functional genomic markers related to life history traits.   The parental stock began with 1500 wild-collected Zebrafish to ensure maximum genetic variation. The design employed three experimental treatments, with two replicates per treatment, and 450 zebrafish per replicate tank.  Harvest rate was 75% per generation.  Treatments were designed to mimic random size selection, minimum size limit (size selective), and maximum size limit (large size selection).  In addition to life history traits, the investigators examined 371 single nucleotide polymorphisms to see if allelic frequencies differed among treatments.

As hypothesized, the minimum length limits had surprising undesired genetic effects. Twenty-two loci showed genetic differentiation and eight of these were statistically significant.   After just five generations of harvesting, adult body size of the Zebrafish shrunk by 7%, which also affected the egg production of the surviving fish. The now-smaller Zebrafish produced fewer and smaller eggs!   Furthermore, the large-selected Zebrafish were significantly more explorative and bolder. This experiment supports a cause-and-effect relationship between size-selective harvest practices and changes in fish life history traits and productivity.  The implications for recovery of overfished populations are important.    

There are at least three options to restore overfished fisheries: (1) moratorium on all harvest; (2) daily creel limits or restrictive size limits, or (3) protect large fecund individuals via a maximum size limit or protected area.  A harvest moratorium rebuilt populations and restored age structure in Atlantic striped bass (Morone saxatilis) (Richards and Rago 1999; Secor, 2000). A transition from minimum length limit to a protected slot limit transformed an extremely truncated size distribution in a smallmouth bass fishery to a trophy fishery (Copeland et al. 2006).  The designation of marine protected reserves is a tool for protecting species from fishing (Bohnsack et al. 2004).   Reserves permit recovery of overexploited fish populations if larval export seeds exploited habitats (Harrison et al. 2012).  

Many commercially or recreationally important fish species have high fecundity and display a weak response between parents and recruits.  Big yearclasses can still be produced by low spawning stocks.  This leaves most fish managers with doubt about strong effects of size selective harvest.  Further, not all fish have the same life history and role. Small fish species should be exploited at levels well below those producing a maximum sustainable yield.  This will provide some forage fish to survive to feed higher trophic levels  (Pikitch et al 2014).  Fishing forage fish intensely increases likelihood of collapse (Essington et al. 2015).

The Atlantic menhaden is exploited with a reduction fishery (i.e, it reduces the catch, into fishmeal and fish oil) and a bait fishery. The fishery expanded from New England after the Civil War to the rest of the coastal states and peaked by 1950, when over 20 reduction factories processed the harvest.  Since the 1960s the menhaden fluctuated and reduction factories closed and reopened, until odor abatement regulations caused most of them to close.  Today a single reduction factory in Reedville, Virginia, processes the landings; Virginia is allocated 85% of the total allowable catch.  Menhaden constitute the largest landings, by volume, along the east coast, and rank second in the U.S behind the Alaskan Pollock. The Atlantic Menhaden were once overfished and sport and commercial fisheries dependent on the Atlantic Menhaden (e.g., Menhaden Defenders) have lobbied hard to change the way this fishery is managed.  Not too many forage fish have their own lobbying group.   Yet, the total allowable catch in recent years is still managed based on single species concepts, as if the Atlantic Menhaden was not eaten by a myriad of fish, mammals, and birds.  Talk about your inappropriate spherical cow!  

Based on the latest stock assessment, the Atlantic menhaden “stock status is not overfished and overfishing is not occurring” (SEDAR 2015).   But nothing in this 643-page assessment addresses the influence of abundance of Atlantic Menhaden on striped bass, bluefish, weakfish, tuna, or other coastal fishes.  Atlantic Menhaden holds the distinction of being the only fish species controlled by the General Assembly and not the Virginia Marine Resources Commission.    The politicians, not the professionals, make decisions. 

The Red Snapper fishery in the Gulf of Mexico collapsed in the late 1980s.  Because the fish and fishery occur in all Gulf states and federal waters, the fishery is managed by the Gulf Fishery Management Council under the authority of the Magnuson-Stevens Fisheries Management Act. The council was slow to enact protections and, therefore, the Red Snapper remained overfished for several decades.  Even in an overfished state, the economic value of the fisheries is $80 million.  The Red Snapper story illustrates why the simple theory was difficult to implement (Cowan et al. 2010).  First, bycatch of juvenile Red Snapper in shrimp trawls was not regulated and caused high mortality among immature Red Snapper.  Second, management plans required the allocation of allowable catch to recreational and commercial fisheries.  Third, regulations such as minimum size limits resulted in regulatory discard mortality, that is fish that are required by law to be released due to size, season, or bag requirements.  Undersized fish had to be released, much to the distress of anglers who assumed that many of the fish, caught from deeper waters and exhibiting protruding swimbladders, would die anyway.  Finally, artificial reefs and oil and gas platforms were deployed in the 1970s and 1980s and used as a red herring, as if the artificial structures would increase Red Snapper abundance (Galloway et al. 2009).   

The Red Snapper is a long-lived species that can live over 50 years, but some will mature at age 3 or 4. The large old fish are highly fecund.  Red Snapper have been called “bet hedgers” as an evolutionary strategy – females produce millions of very small eggs over her lifetime, with an infinitesimally small chance of surviving to be an adult Red Snapper.
Concept Map depicting cause and effect relationships of big old fat fecund female fish (BOFFF; Hixon et al. 2013)
Intense exploitation in the Gulf fishery truncates the age distribution such that few fish over 5 years old survive.  Fish are gaining weight at a very high rate at this age range from 5 to 20 years.  Also the fecundity is much higher for these big old fat fecund female fish  (BOFFFF; Hixon et al. 2013).  Older red snapper also spawn more frequently and a 32-inch female produces 24 times as many eggs as a 16-inch female (Porch et al. 2013).  
Growth and age distribution of Red Snapper in the Gulf of Mexico (Cowan et al. 2010).

One major factor affecting recruitment of Red Snapper is periodic occurrence of hypoxia, which caused the loss of all red snapper and most of the invertebrates on and around the reefs in 2001 (Workman and Foster 2002).   Since this periodic recruitment failure is an expected occurrence, it makes sense to maintain a larger spawning stock biomass so that large year classes of Red Snapper may be produced in good years.
Texas State record Red Snapper (40 pounds) caught June 1, 2014. Source
Yet the Red Snapper population has not recovered.  It took a long time to implement bycatch reduction in the shrimp trawlers.  Then many years later gear restrictions were implemented to limit hooking mortality and require gas bladder venting.  Yet only 72% of discarded Red Snapper survived after being released (Curtis et al. 2015).   Area closures in zones occupied by BOFFF Red Snapper have never been used; yet the closure of the area to fishing would reduce wasteful discards and discard mortality.  Yet the trend in fish biomass indicates only minor recent recovery.  The SEDAR Update (Gulf Fishery Management Council 2015) revealed that the stocks remain at historical lows and the age distribution is truncated.   Decisions made by the council have had a very high opportunity cost in terms of loss of fishery values over the past decades.

These three fishes teach us a lot about exploited populations of fish.  Any assessment of the status of an exploited fish population and evaluation of alternative management strategies requires certain assumptions.  However, sometimes I feel like choking on the spherical cow.   As we move forward we need to apply lessons learned from other fisheries and follow common sense (KISS) principles.

·      Little fish feed the world. Total allowable catch should be adjusted based on needs of predators or ecosystem services provided.
·      Protect the BOFFFF -- they survive unfavorable recruitment times and facilitate resilience.
·      Size-selective harvesting causes changes in key life-history traits, leading to low maximum body size and poor reproductive output.
·      Intense fishing selects for shy behaviors.
·      Effects of fishing proceed at a faster pace than the scientific approach to evaluating actions. The best available science often adopts simplifying assumptions.

Arlinghaus, R., S. Matsumura, and U. Dieckmann 2010. The conservation and fishery benefits of protecting large pike (Esox lucius L.) by harvest regulations in recreational fishing. Biological Conservation 143:1444–1459.
Beverton, R.J.H., and S.J. Holt. 1957. On the Dynamics of Exploited Fish Populations. Ministry of Agriculture, Fisheries and Food, London.
Bohnsack, J.A., J.S. Ault, and B. Causey. 2004. Why have no-take marine protected areas?   
Copeland, J.R., D.J. Orth, and G.C. Palmer. 2006. Smallmouth bass management in the New River, Virginia: a case study of population trends with lessons learned. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 60:180-187.
Cowan, J.H. and fourteen coauthors.  2010. Red snapper management in the Gulf of Mexico: science- or faith-based? Reviews in Fish Biology and Fisheries      DOI 10.1007/s11160-010-9165-7   
Curtis, J.M., M.W. Johnson, S.L. Diamond, and G.W. Stunz. 2015. Quantifying delayed mortality from barotrauma impairment in discarded Red Snapper using acoustic telemetry.  Marine and Coastal Fisheries 7(1):343-349.  DOI: 10.1080/19425120.2015.1074968
Essington T.E., and seven coauthors. 2015. Fishing amplifies forage fish population collapses. Proceedings of the National Academy of Science USA 112:6648–6652.    
Galloway, B.J., S.D. Szedlmayer, and W.J. Gazey. 2009.  A life history review of red snapper in the Gulf of Mexico with an evaluation of the importance of offshore petroleum platforms and other artificial reefs. Reviews in Fisheries Science 17(1):48-67.
Gulf Fishery Management Council, Science and Statistical Committee.  2015. SEDAR Red Snapper 2014 Update Assessment, Charleston, SC  242 pp.
Harrison H. B., Williamson D. H., Evans R. D., Almany G. R., Thorrold S. R., Russ G. R., Feldheim K. A., et al. 2012. Larval export from marine reserves and the recruitment benefit for fish and fisheries. Current Biology 22:1023-1028.
Heino, M., L. Baulier, D. S. Boukal, B. Ernande, F. D. Johnston, F. M. Mollet, H. Pardoe et al. 2013. Can fisheries-induced evolution shift reference points for fisheries management? ICES Journal of Marine Science 70:707–721.
Hixon, M.A., D.W. Johnson, and S.M. Sogard. 2013. BOFFFFs: on the importance of conserving old-growth age structure in fishery populations. ICES Journal of Marine Science.  doi: 10.1093/icesjms/fst200   
Hutchings, J. A. 2009. Avoidance of fisheries-induced evolution: management implications for catch selectivity and limit reference points. Evolutionary Applications 2:324–334.
Pikitch, E.K., and nineteen coauthors. 2014. The global contribution of forage fish to marine fisheries and ecosystems. Fish and Fisheries 15(1):43-64. doi:10.1111/faf.12004
Porch, C.E., G.R. Fitzhugh, and B.C. Linton.  2013.  Modeling the dependence of batch fecundity and spawning frequency on size and age for use in stock assessments of red snapper in U.S. Gulf of Mexico waters.  National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, Florida.  SEDAR 31-AW report.  20 pp 
Reed, W.J. 1980. Optimum age-specific harvesting in a nonlinear population model. Biometrics 36(4):579-593.
Richards, R.A. and P.J. Rago. 1999. A case history of effective fishery management: Chesapeake Bay Striped Bass. North American Journal of Fisheries Management 19:356-375.
Ricker, W.E. 1981. Changes in the average size and average age of Pacific Salmon. Canadian Journal of Fisheries and Aquatic Sciences. 38(12): 1636-1656
Rijnsdorp A. D., C.J.G. van Damme C. J. G., and P.R. Witthames. 2010. Implications of fisheries-induced changes in stock structure and reproductive potential for stock recovery of a sex-dimorphic species, North Sea plaice. ICES Journal of Marine Science 67:1931-1938.
Secor, D.H. 2000. Longevity and resilience of Chesapeake Bay striped bass.  ICES Journal of Marine Science 57: 808–815. doi:10.1006/jmsc.2000.056
SEDAR. 2015.  SEDAR 40  - Atlantic Menhaden stock assessment report.  SEDAR, North Charleston, SC 643 pp.  available online at:
Sharpe, D. M. T., and A. P. Hendry 2009. Life history change in commercially exploited fish stocks: an analysis of trends across studies. Evolutionary Applications 2:260–275.
Silliman R. P. 1975. Selective and unselective exploitation of experimental populations of Tilapia mossambica. Fishery Bulletin 73:495-507
Uusi-Heikilla, S., and 13 coauthors.  2015. The evolutionary legacy of size-selective harvesting extends from genes to populations. Evolutionary Applications doi:10.1111/eva.12268

Workman, I.K., and D.G. Foster. 2002.  The webbing reef: a tool used in the study of juvenile red snapper (Lutjanus campechanus).  Oceans '02 MTS/IEEE Conference. Pp. 146-150. 10.1109/OCEANS.2002.1193262

Friday, February 19, 2016

Hoki Fish: A Potential Fishy College Mascot? By Don Orth

What college has the dumbest mascot?   This Bleacher Report post includes the Virginia Tech Hokies among the 23 dumbest mascots.  (Full Disclosure, I have two degrees from Oklahoma State University where the mascot for the Cowboys is a crusty old cowboy named Pistol Pete.  Before Pistol Pete, they struggled for 35 years as Agriculturists or Aggies, the Farmers, and officially but unpopularly, the Tigers)    I am not a big fan of these lists and rankings. This post makes me wonder who David Luther is and what criteria and evidence he used to develop the list.  But Mascots can and do change.  There may be a new fish in Virginia Tech's future.

Virginia Tech’s original mascot, the Gobbler, was so lame that it was eventually replaced by the Hokie.  But what's a hokie, you ask? The name comes from an early 20th century cheer.

Hoki, Hoki, Hoki, Hy.
Techs, Techs, V.P.I.
Sola-Rex, Sola-Rah.
Polytechs - Vir-gin-ia.
Rae, Ri, V.P.I.

The Hokie bird mascot, resembling a maroon and orange turkey-like bird, is much beloved by today’s Hokies.  Since the last makeover in 1987, the Hokie Bird has maintained a consistent look.  You can follow the Hokie bird mascot @TheHokieBird on Twitter along with 16,700 other followers! The purpose of a mascot is to inspire fans.  If a mascot is working, then there is no reason to change. But the mascot changed once, it could happen again.  Couldn’t it?  The Hokie Bird is very busy and Virginia Tech is expanding; perhaps a Hokie Fish would be a welcome helper.
Virginia Tech's Hokie Bird mascot.  Source

But what fish would have wide appeal?  Is there a Hokie fish?  Few colleges have fish as mascots.  There the Palm Beach Atlantic University Sailfish, Muskegum Muskies, University of Virginia Wahoos, and the Fighting Salmon.   If Virginia Tech selected a fish, would it be Brook Trout, Blacknose Dace, Bluehead Chub, Walleye, or Flathead Catfish?   Each of these fish has strong local connections to habitats.  The Brook Trout is the icon of high elevation Appalachian mountain streams.  Blacknose Dace is more widespread, occurring in small streams from the mountains to the urban streams; it should be the official fish of Blacksburg since it dominates in Stroubles Creek and tributaries.  The Bluehead Chub is another local favorite due to its macho head tubercles and gravel-mound building habits.  "Chubby" appears on Blacksburg parade floats since 2015The Walleye is a terrific food and sport fish and a unique river-spawning form exists in the upper New River.  But if you want a big, tough mascot I suggest you pick the Flathead Catfish, a large fish-eating catfish that grows as large as a VW (No, not quite.).  

There is a fish named the Hoki. At least at the fish market, the Blue Grenadier Macruronus novaezelandiae (Hector 1871) is referred to as the Hoki.  Is the Hoki fishery cutting it? Would it be a worthy mascot?  The Blue Grenadier, is a member of the merluccid hakes (Merlucciidae) in the order of cods (Gadiformes).  
Blue Grenadier Macruronus novaezelandiae (Hector 1871) or Hoki. Source.
The Blue Grenadier (aka Hoki ) schools in the mesopelagic zone in waters from 200-700 m deep.  The body form is very elongate and compressed with a tapering tail, dorsal and anal fins confluent with the caudal fin.  It is a visual predator with large eyes.   The long body provides for a long lateral line and that distant touch sense.   It might be a challenge to develop an anthropomorphic Hoki Fish design.  It certainly is no Charlie the Tuna.  

The Hoki’s habitat, the mesopelagic zone, is a difficult environment even for a fish.   To begin with there is insufficient light for photosynthesis. So consumers must rely on poop or detritus from the epipelagic zone, or they must expend limited energy reserves to migrate up into epipelagic zone to find food and do this at night to avoid predators. Second, it's cold, very cold, only 4-8°C.  Oxygen levels at these depths are at minimal levels, so metabolism is slow and, perhaps, life is boring for the Hoki.  The Hoki must grow to 65-70 cm to reach sexual maturity; it takes 4-7 years.  The Hoki can reach 120 cm and 1.5 kg, but that may take a long time, up to 25 years!

With it's large toothy mouth, the Hoki feeds on a variety of small fishes, especially lanternfishes (family Myctophidae), crustaceans such as prawns, euphausiids, galatheids, and squids (Bulman and Blaber 1986; Brickle et al. 2009; Connell et al. 2010)
Common diet items of the Hoki.  Top row: Natant decapods, Squat Lobster (Galatheidae), Shrimp (Pasiphaeidae), and Krill (Ephausiidae)   Second row: Marine Hatchetfish (Sternoptychidae),  Slender Lanternfish (Gonichthys barnesi),  Thorntooth Grenadier (Lepidorhynchus denticulatus) Third row: Silver lighthouse fish (Photichthys argenteus), squid (Lycoteuthis lorigera)
The Hoki must move up in the water column to feed at night. Vertical migration is an adaptation of many mesopelagic fish and invertebrates (Watanabe et al. 1999). These vertical migrations often occur over a large vertical distance with the aid of a physoclistous swim bladder.  They appear to follow migrations of other mesopelagic fish prey.  McClatchie et al. (2005) found that "catch rate of hoki was correlated with the abundance of vertically migrating mesopelagic fish.”  One would think these fish would be safe from humans.  But we humans love our fish nuggets and fish sticks, so even deepwater fish are harvested.

The Hoki is one of the most valuable New Zealand fisheries, where catches since 1987 ranged between between 200,000 and 250,000 tonnes (Coombs and Cordue 1995). It is also an important commercial fish off Victoria and Tasmania in Australia. Much of the fish in the McDonald's Fillet-O-Fish Burger sold in Australia (and all of it in New Zealand) is the Hoki.     McDonald’s in North America used to use the Hoki, but stopped using Hoki in 2013 in favor of Alaskan pollock. Another species of Hoki is harvested off Argentina.  The Argentine Hoki (Macruronus magellanicus) fishery received Marine Stewardship Council (MSC) certification in May 2012

Hoki are caught using bottom and midwater trawl gear towed from large trawlers. Travel to New Zealand and watch a Hoki trawler in action.  Is the Hoki fishery sustainable?  There are problems with this fishery.  Bycatch of seals and seabirds  (albatrosses and petrels) is a major problem.  The seals and seabirds are attracted to fishing vessels as an opportunistic source of food.  "The New Zealand fishery kill 200-300 fur seals per year. The Australian fishery is limited to 30 seal deaths per year. Both fisheries are implementing seal exclusion devices to reduce seal bycatch.   Seabird bycatch is more difficult to reduce. 

After the Hoki fishery was first certified in 2001, the Royal Forest and Bird Protection Society of New Zealand filed an objection with MSC and requested that certification be withdrawn.  By 2007, several conditions were placed on the fishery with regard to seabird bycatch and by 2010 the Hoki fishery was not killing a lot of seabirds (Deepwater Group Limited 2011; Wiedenfeld 2012).   

The Marine Stewardship Council, is a non-profit organization that certifies fisheries sustainability based on three principles, namely (1) Sustainable fish stocks; (2) Minimizing environmental impact; and (3) Effective management (Marine Stewardship Council 2010).  Each fishery is scored based on 31 performance indicators.  Fisheries that want the certification pay US$20,000 to more than $100,000 to an independent, for-profit contractor that assesses the fishery against the MSC standards and determines whether to recommend certification.   Is this an automatic conflict of interest based on a self-serving free market entity? Or is it a viable free market solution for sustainable solution (Jacquet et al. 2010)?  At the moment, the MSC is the dominant organization certifying sustainability for wild-capture fisheries for sale at markets, such as Whole Foods Market.   Alternatives, such as The Safina Center’s Sustainable Seafood program, do exist.
Hoki Spawning stock biomass trajectories approach the sustainability target of 35-50% of long-term spawning biomass in absence of fishing.  DeepWater Group Limited 2011.
While the Hoki is a large and important commercial fish and its fishery is working towards sustainability goals, I don't think I can generate enthusiasm for naming a Hoki Fish as a new or additional Virginia Tech mascot. The "You're not from around here" sentiment may be too strong.   The Hokie Bird is wildly popular and one of the proud VT traditions. Plus the Hokie Bird reminds us of the eastern Wild Turkey conservation success story.   So it turns out that David Luther is wrong; Hokie Bird is not a dumb mascot.   But the idea of a Hokie Fish mascot is one that needs further work.  If you have a good fish to nominate, please comment here. 


Bulman, C.M., and S.J.M. Blaber.1986. Feeding ecology of Macruronus novaezealandiae (Hector) (Teleostei : Merluciidae) in south-eastern Australia. Australian Journal of Marine and Freshwater Research 37: 621-639
Connell, A.M., M.R. Dunn, and J. Forman. 2010. Diet and dietary variation of New Zealand hoki Macruronus novaezelandiae.   New Zealand Journal of Marine and Freshwater Research  44(4):289-308.
Coombs, R.F., and P.L. Cordue. 1995. Evolution of a stock assessment tool: acoustic surveys of spawning hoki () off the west coast of South Island, New Zealand, 1985–1991. New Zealand Journal of Marine and Freshwater Research 29: 175–194.
DeepWater Group Limited.  2011.  Sustainable management of New Zealand’s Hoki fisheries      
Jacquet, J. D., D. Pauly, S. Ainley, S. Holt, P. Dayton, and J. Jackson.  2010. Seafood stewardship in crisis. Nature 467 (7311): 28–29. doi:10.1038/467028a
Marine Stewardship Council. 2010.  Principles and Criteria for Sustainable Fishing.    available at
McClatchie, S., M. Pinkerton, and M.E. Livingston, 2005. Relating the distribution of a semi-demersal fish, Macruronus novaezelandiae, to their pelagic food supply. Deep-sea Research I: Oceanographic Research Papers 52:1489–1501.
Watanabe, H., M. Moku, K. Kawaguchi, K. Ishimaru, and A. Ohno. 1999. Diel vertical migration of myctophid fishes (Family Myctophidae) in the transitional waters of the western North Pacific. Fisheries Oceanography 8(2):115-127
Wiedenfeld, D.A. 2012. Analysis of the effects of Marine Stewardship Council fishery certification on the conservation of seabirds.  American Bird Conservancy.  The Plains, Virginia.  40 pp.