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Competition between Marine and 8CHAPTER : Food for Thought

Kristin Kaschner and

This chapter is adapted from “Competition between Marine Mammals and Fisheries: Food for Thought” published by The Humane Society of the /Humane Society International. Introduction arine mammals and soon extended all the way to Antarc- gered Wildlife in Canada 2003). On have co-existed tica and reduced countless popula- the other hand, there are examples Mon this planet for several tions to small fractions of their for- of some marine mammals potential- hundred thousand years. Both rely mer abundance (Perry, DeMaster, ly adversely affecting fisheries. Con- heavily on the exploitation of and Silber 1999) or wiped them out troversial cases include damaging of marine resources, though , completely, as with the now-extinct gear (e.g., harbor seals vs. fish dolphins, and have been Atlantic gray (Mitchell and farms) (Johnston 1997; Fertl 2002), doing so for much longer, roaming Mead 1977) or the Caribbean monk devaluation of catch through de- the oceans for millions of years, seal (Kenyon 1977; Gilmartin and predation (killer whales vs. long- long before the emergence of mod- Forcada 2002). Today, humans ad- line fisheries in Alaska) (Dahlheim ern humans (Hoelzel 2002). It is versely affect marine mammals 1988; Fertl 2002), or, indirectly, not surprising that, when there is a mainly through incidental entangle- through costs incurred by gear “new kid on the block,” co-exis- ment in gear (Northridge modifications that are required to tence is not always very peaceful, 1991, 2002; Harwood et al. 1999; reduce anthropogenic impacts on and many of the encounters Kaschner 2003), chemical (Mossner marine species (e.g., dol- between humans and marine mam- and Ballschmiter 1997; Borrell and phin-excluder devices, pingers) mals result in a variety of conflicts. Reijnders 1999; Coombs 2004) and (Harwood 1999; Palka 2000; Read acoustical (Johnston and 2000; Culik et al. 2001). Woodley 1998; Jepsen et al. 2003), Room for and, in some cases, ship strikes Is Competition Conflict (Clapham, Young, and Brownell a Problem? 1999; Fujiwara and Caswell 2001). Many species of marine mammals Competition between marine Some populations close to the point are affected and frequently threat- mammals and fisheries for available of are the vaquita (D’A- ened by fisheries and other marine food resources has often grosa, Lennert-Cody, and Vidal activities (Northridge 1991, 2002). been mentioned as another issue of 2000), the Mediterranean (Aguilar In the past the main threats were concern (Beddington, Beverton, 1998; Ridoux 2001; Gucu, Gucu, large-scale (Clapham and and Lavigne 1985; Harwood and and Orek 2004) and Hawaiian monk Baker 2002) and sealing operations Croxall 1988; Plagányi and Butter- seals (Carretta et al. 2002), and the (Gales and Burton 1989; Knox worth 2002). This is understand- western North Atlantic 1994; Rodriguez and Bastida 1998). able, since many (Perry, DeMaster, and Silber 1999; These focused initially on the waters species, in common with humans, Committee on the Status of Endan- of northern Europe and Asia, but operate near or at the top of the

95 marine food web (Pauly et al. worth 2002). A rarely acknowledged they largely ignore important issues 1998b). In recent years, as the fish- but implicit assumption is that of uncertainty and food web interac- eries crisis has developed from a set removal of one of the players would tions (Harwood and MacLaren of regional problems to a global translate into direct benefits for the 2002; International Whaling Com- concern (Pauly et al. 2002, 2003), remaining player. In the context of mission 2003). However, the appli- and the protein that mil- the proposed competition between cation of more complex models, lions of people depend on is in marine mammals and fisheries, such as those recommended by the increasingly shorter supply, there is competition occurs when both ma- United Nations Environment Pro- a growing need to find scapegoats rine mammals and fisheries con- gramme to investigate proposals for for the collapse of fisheries. Most sume the same types of food in the marine mammal culls (1999), is marine mammals are large—sug- same general geographical areas often hampered by the lack of avail- gesting that they must eat a great (and water depths). More important ability of necessary data (Tjelme- deal—and visible to us, at least in though, competition occurs only if land 2001; Harwood and MacLaren comparison with other marine top the removal of either marine mam- 2002; International Whaling Com- predators, such as piscivorous fish. mals or fisheries results in a direct mission 2003) and the degree of Moreover, some species—notably increase in food available to the uncertainty associated with their various species of fur seals (Torres other (Cooke 2002; International parameters. 1987; Wickens and York 1997)— Whaling Commission 2003). It has been suggested that an have recovered from previous levels undesired consequence of the of high exploitation and their popu- Measuring Competition efforts to focus on the uncertain- lations are increasing, although Many studies have attempted to ties and difficulties associated with population levels of most species qualitatively and quantitatively the application of complex models are still far below their pre-exploita- assess the ecological role of marine has been an effective rejection of tion abundance (Torres 1987; mammals and the extent of their the “scientific approach” by politi- Wickens and York 1997; Perry, trophic competition or overlap with cians, administrators, fishers, and DeMaster, and Silber 1999). For fisheries (Harwood and Croxall laypeople. Thus many people end these reasons, whales, dolphins, 1988; Sigurjónsson and Vikingsson up considering the simpler “who- and pinnipeds are likely culprits 1992; Bowen 1997; Trites, Chris- eats-how-much-of-what” approach behind the problems various fish- tensen, and Pauly 1997; Hammill as a “commonsense” notion where- eries are facing. Thus the voices of and Stenson 2000; Thomson et al. in fewer marine mammals must countries and corporations with 2000; Yodzis 2001; Boyd 2002). To mean more fish for humans to large fishing interests, requesting address this question, various catch (Holt 2004). As another side “holistic management” that approaches have been applied to effect of their data requirements, includes “the utilization of marine the problem of modeling marine most complex models focus on rel- mammals such as whales...to mammal food consumption and the atively small geographic areas increase catch from the oceans” potential effects of this intake on (Stenson and Perry 2001; Bjørge et (Institute of Cetacean Research yields, reviewed in detail al. 2002; Garcia-Tiscar et al. 2003). 2001a, n.p.), have been growing elsewhere (Cooke 2002; Harwood Although this may suffice for some louder. As a consequence, much and MacLaren 2002; International coastal species, such small scales political pressure has been applied Whaling Commission 2003 ). Exist- may be inappropriate for species in recent years in various interna- ing approaches range from simple, that are highly migratory and tional fora concerned with the static “who-eats-how-much-of-what” range globally or across large management of global marine models to very sophisticated troph- ocean basins. As a result, percep- resources to begin to address com- odynamic models that tion of the extent of the problem in petition between marine mammals consider, among other things, inter- terms of resource overlap between and fisheries on a global scale (van actions among multiple species fisheries and marine mammal Zile 2000; Food and Agriculture changing over time and in space species is distorted by models that Organization of the United Nations (Bogstad, Hauge, and Ulltang 1997; are restricted to areas that repre- 2001; Holt 2004). International Council for the Explo- sent only a fraction of a species’ ration of the Sea 1997; Bogstad, distributional range. What Is Competition? Haug, and Mehl 2000; Christensen We propose a different type of From an ecological perspective, and Walters 2000; Livingston and approach, allowing some perspec- competition is a situation where the Jurado-Molina 2000). The “who- tive on the issue of potential com- simultaneous presence of two eats-how-much” models generally petition between fisheries and resource consumers is mutually dis- are regarded as inadequate to inves- marine mammals on a global scale. advantageous (Plagánzi and Butter- tigate potential competition since By developing further the “who-

96 The State of the III: 2005 eats-how-much-of-what” approach, and are referred to here as the body mass (Boyd 2002; Leaper and we can demonstrate that the appli- “naïve” approach. These models Lavigne 2002). However, we still cation of some true common calculate the quantity of prey know very little about the factors sense1 may be sufficient to counter taken by marine mammal species that influence this relationship, claims that culling marine mam- by simply estimating the amount and the naïve approach effectively mals will help us alleviate the of food consumed by one animal of ignores the large variations among major problems the world’s fish- a specific species based on its esti- individuals and species associated eries are facing today, and even mated mean weight, multiplying with differences in age and sea- world hunger. this amount by the total estimated sons, and the proportion of time number of animals of this species, spent on different activities, to and then summing this estimate of mention only a few. More impor- What We Do food intake for all or major sub- tant, the naïve approach complete- In this essay we summarize the groups of marine mammal species. ly ignores the complex range of major flaws in the case for culling, Estimates thus derived put the dynamic factors that affect how put forward at international fora total amount consumed by removal of high-level predators with increasing insistence, which cetaceans worldwide, for instance, affects ecosystems (Parsons 1992), blames marine mammals for the at three to six times the global some of which we discuss later. For world’s fisheries crisis and pro- marine commercial fisheries catch all of these reasons, gross esti- motes the pre-emptive removal of (Institute of Cetacean Research mates of the total amount of fish marine mammals as a solution to 2001b; Tamura 2003). As a result consumed by marine mammals, by problems such as globally dwin- it is often implied that a reduction themselves, provide little or no dling and world hunger. in the predator population will information about the net “gain” More important, however, we show translate directly into a correspon- in fisheries catches that might that, even though this group of ding increase in prey (Kenney et al. result from a reduction in numbers predators does collectively con- 1997; Sigurjónsson and Viking- of any marine mammal population. sume a large quantity of marine soon 1997; MacLaren et al. 2002; resources as part of its natural role Tamura 2003) and that this But for the Sake in marine ecosystems, there is like- increase would then be available of Argument... ly very little actual competition for fisheries exploitation. It may seem intuitive that, because between “them” and “us,” mainly whales and other marine mammals because marine mammals, to a Problems with the are big and eat a great deal, having large extent, consume food items Naïve Approach fewer of them should result in that humans do not catch and/or There are many problems associat- more fish being available for consume them in places where ed with the naïve approach—so human consumption. There is as fisheries do not operate. many that the scientific communi- yet no model that is detailed ty has effectively refused even to enough and meets sufficiently Who Eats How consider a discussion about culling stringent scientific requirements marine mammal species based on that would allow us to reliably MUCH? these simple estimates (Interna- investigate the effects, positive or tional Whaling Commission 2003). negative, that reduction of marine The Naïve Approach One problem is that reliable and mammal populations might have Substantial political pressure has comprehensive abundance esti- on net fisheries catches. Indeed, been applied in recent years to pro- mates are still lacking for the such a model may never be devel- mote the claim that competition majority of marine mammal oped. Therefore, rather than focus- between marine mammals and species throughout much of their ing our efforts on attempting to do fisheries is a serious global issue distributional ranges—most global what probably cannot be done, we that needs to be addressed in the estimates represent only guessti- instead show the flaws in the argu- context of world hunger in general mates at best. Moreover, since we ments that favor resumption of and dwindling fish stocks specifi- cannot directly measure the whaling using the naïve ap- cally (van Zile 2000; Food and Agri- amount of food consumed by the proach—based on commonsense culture Organization of the United animals, our estimates of food considerations and a few addition- Nations 2001; Holt 2004). These intake rely on physiological models al parameters. claims are based on very simplistic that are largely based on what we We used a simple food consump- food consumption models—crude know about the relationship be- tion model, outlined briefly in the so-called surplus yield calculations tween the amount an animal must sidebar on page 98, to estimate (Harwood and MacLaren 2002)— eat to sustain itself given a certain global annual food consumption of Competition between Marine Mammals and Fisheries: Food for Thought 97 all marine mammals due to their large size. However, in terms of the Basic Food Consumption type of food targeted also by fish- Model: Who Is Eating How eries (shown in red in Figure 1; mostly small pelagics, benthic Much of What? invertebrates, and a group we have dubbed “miscellaneous fishes,” We generated estimates of annual eries are probably closer to 150 mil- which mainly includes medium- food consumption during the 1990s lion tons per year, if illegal, unreport- sized groundfish and for each marine mammal species ed, or unregulated (IUU) catches species), whales likely con- using a simple food consumption are taken into account (Pauly et al sume less or at least no more than model17 (Trites, Christensen, and 2002) (Figure 1). The percentages fisheries do every year. The majori- Pauly 1997) and syntheses of of different food types in total ty of what baleen whales (as well as recently published information marine mammal consumption were toothed whales and pinnipeds) eat about the population abundances, estimated based on the diet com- consists of food types that, for rea- sex ratios, sex-specific mean position standardized across sons of taste and accessibility, are weights, and weight-specific feed- species, itself based on two hun- of little interest to commercial ing rates extracted from more than dred published qualitative and quan- fisheries. We expand on this im- three thousand sources of primary titative studies of species-specific portant consideration of what is and secondary literature compiled feeding habits (Pauly et al. 1998a). being eaten in the next section. into a global database. To convey The proportions of different food the extent of uncertainty associated types represented in fisheries Who Eats How with this total estimate of marine catches were obtained by assigning mammal food consumption, we individual target species/taxa to the Much of What? generated minimum and maximum appropriate food type category estimates by running the model based on life history, size, and habi- Different Species, with different feeding rates but tat preferences of the target Different Strokes ignoring effects such as seasonal species or taxa. Food types includ- During their foraging dives, many differences in food intake (Kaschner ed benthic invertebrates (BI), large marine mammal species regularly 2004). Corresponding mean global zooplankton (LZ), small squid (SS), venture to depths of more than a fisheries catches for the 1990s large squid (LS), small pelagic fishes thousand meters (Campagna et al. were taken from the global fish- (SP), mesopelagic fish (MP), miscel- 1998; Hooker and Baird 1999; Hin- eries catch database developed and laneous fish (MF), higher verte- dell et al. 2002; Laidre et al. 2003) maintained by the Sea Around Us brates (HV), and an additional food and far under the pack ice (Davis Project at the Fisheries Centre (Uni- type containing all catches of et al. 2003), into areas rarely if versity of British Columbia, Canada) species targeted only by fisheries, ever visited by humans. There, they (sidebar on page 100) and averaged such as large tuna, which we called feed on organisms about whose over the last decade. Note that this non-marine mammal fishes (NM) existence we often know only indi- is an estimate of only the reported (Figure 2). rectly based on specimens collect- catches and that total takes by fish- ed from the stomachs of marine mammal species (Fiscus and Rice 1974; Clarke 1996). different groups of marine mam- estimates generated by the model, Along similar lines, at least some mals to compare them with catch- which illustrate the wide margin of our favorite delicacies, es taken by world fisheries (Figure for error that must be considered such as tuna, are rarely if ever con- 1). Mean estimates for all groups before attempting to use such es- sumed by marine mammals. In are indeed almost as high as or timates in a management context. light of these and many other dif- slightly higher than global report- We arrive at maximum estimates ferences in taste and accessibility, ed fisheries catches (although it of global mean food intake for the distinction between which food should be noted that total fish- baleen whales that are similar to types are targeted by marine mam- eries catches are likely underesti- those published previously (Insti- mals and which by fisheries war- mated (Pauly et al. 2002). To con- tute of Cetacean Research 2001a; rants serious attention. Based on vey—at least to some extent—the Tamura 2003). Although there are the approach described in the side- degree of uncertainty associated comparatively few of this species,2 bar at left, we specified the relative with these estimates, we have also baleen whales do, indeed, take the amount of nine different food types included minimum and maximum bulk of the total food consumed by

98 The State of the Animals III: 2005 Figure 1 Who Eats How Much?

Estimated mean annual global catch/food consumption of fisheries and major marine mammal groups during the 1990s (modified from Kaschner 2004). Error bars of marine mammal food consumption indicate minimum and maximum estimates based on different feeding rates (Leaper and Lavigne 2002). Total fisheries catches are probably closer to 150 million tons per year if illegal, unreported, and unregulated catches are taken into account (Pauly et al. 2002). Marine mammals’ food intake consisting of prey types that are also major groups targeted by fisheries are presented in red (mainly small pelagic fishes, miscellaneous fishes, and benthic invertebrates). Note that, although mean global food consumption of all marine mammals combined is estimated to be several times higher than total fisheries catches, the majority of food types the various marine mammal groups consume are not targeted by fisheries. consumed by major marine mam- Size—among Other readily digested than those of other mal groups and fisheries (Figure Things—Matters prey groups (Zeppelin et al. 2004). 2). The majority of all food con- Such biases may be addressed by Like all other parameters in the sumed by any marine mammal applying correction factors that basic food consumption model, the group consists of food types that compensate for differential effects marine mammal diet composition are of little interest to commercial of digestion on different prey types is affected by uncertainties. Prob- fisheries. Diets of pinnipeds and (Tollit et al. 1997, 2003). More seri- lems arise due to the difficulties dolphins appear to be most similar ous biases are introduced by the associated with obtaining diet infor- to global fisheries catch composi- predominance of stranded animals mation from sufficient sample sizes tion, while the diet of large in the overall sample. Such animals in the wild (Barros and Clarke toothed whales, which feed pre- may not be representative of the 2002). Diet composition estimates dominantly on large, deep-sea rest of the population, as they are based on stomach content analyses squid species not targeted by fish- often sick and/or their stomach tend to be biased toward cephalo- eries (Clarke, Martins, and Pascoe contents over-represent the coastal pods, as their hard parts are less 1993), shows the least similarity. components of their diet (Barros

Competition between Marine Mammals and Fisheries: Food for Thought 99 sonal variation in the diet composi- tion of marine mammal species Modeling and Mapping of (Haug et al. 1995; Nilssen 1995; Global Fisheries Catches— Tamura 2001). The standardized diet composi- You Couldn’t Have Caught tion used here may be fairly robust to these sources of bias/uncertain- That There! ty, as the food type categories are very broad.3 However, due to these Until recently, the exact origin of fish- can serve to limit the available area biases, the similarity in food types eries catches of the world was most- where reported catches can be exploited by fisheries and marine ly unknown. The reasons were made within the large statistical area. mammals shown in Figure 2 is like- many, and where fisheries landing We developed and used a global ly to be even lower than suggested statistics exist (and they do, in some database of species distributions here,4 especially if other aspects, form, for the overwhelming majority based on published maps of occur- such as differences in prey size, are of the world’s fisheries), they usually rence (where available) or by using taken into consideration as well. suffer from a number of deficiencies. other sources of information to help Ignoring typical problems of miss- restrict the range of exploited taxa, ing/incomplete data and inconsistent notably water depth (for non-pelagic Who Eats How units of measure, one of their most species), latitudinal limits, statistical common weaknesses is that they areas, proximity to critical habitats Much of What are often quite vague, particularly (such as seamounts, mangroves, or WHERE? about the identity of the harvested coral reefs), ice coverage, and histor- The spatial overlap of resource taxa as well as the exact location ical records. In addition, we compiled exploitation is necessary for com- where they were caught. To over- large amounts of information de- petition to occur. In this section, come this problem, over the past scribing the access agreements we assess the degree of overlap four years, the Sea Around Us Pro- between fishing nations to the fish- between marine mammal food ject has developed a spatial alloca- eries resources of other coastal consumption and fisheries by com- tion process that relies on what countries based on formal bilateral paring on a global scale the areas might be called the application of agreements, existing joint ventures where marine mammals are likely common sense (in conjunction with between governments and private to feed to the areas in which most very large amounts of related data companies and/or associations, and fishing activities occur. stored in supporting databases) to the documented assign the coarse-scale reported before the declaration of exclusive Where Are Fisheries? landings from large statistical areas economic zones by various coun- To illustrate where most human into the most probable distribution tries and other observations. The fishing activities occur, we used the within a global grid system with 0.5° intersection of these databases mapped distribution of global fish- latitude by 0.5° longitude cell dimen- with reported catches by countries eries for an average year during the sions (approximately 180,000 ocean from large statistical fishing areas 1990s (Figure 3) using a modeling cells). The basic assumptions are allows the allocation of fine-scale process described briefly in the that catches of a particular fish fisheries catches to individual spa- sidebar at left. As can be seen, the species (or other harvested taxa) by a tial cells. Predicted catch and bio- vast majority of fisheries catches is specific country cannot occur where mass distributions of taxa exploited taken along the continental shelves the reported species does not occur, by fisheries of the world can be of Europe, North America, South- and that they cannot stem from viewed online at www.seaaround- east Asia, and the west coast of areas where the country in question us.org, and average catch distribu- South America. Highest catches is not allowed to fish. Therefore, tion for the 1990s is shown in Fig- occur where continental shelves information about species distribu- ure 3. (This sidebar is generally are wide, such as the Bering, East tions and fishing access agreements adapted from Watson et al. 2004.) China, and North seas, or in highly productive systems, such as those that can be found along and Clarke 2002). Other, newer er et al. 2001; Lea et al. 2002; the west coasts of South America molecular methods, including sta- Grahl-Nielsen et al. 2003) analyses, and . However, despite ble isotope (Best and Schell 1996; also have biases (Smith, Iverson, the distant water fleets roaming the Hooker et al. 2001; Das et al. 2003) and Bowen 1997). Finally, there is oceans and the development of and fatty acid (Iverson 1993; Hook- substantial geographical and sea- deep-sea fisheries operating far off-

100 The State of the Animals III: 2005 Figure 2 Who Eats How Much of What?

Estimated mean annual global catch/food consumption of marine mammals and fisheries by nine major food types during an average year in the 1990s expressed as proportions of total (from Kaschner 2004). The percentages of different food types in marine mammal consumption were computed based on diet composition standardized across species (Bonfil et al. 1998). Corresponding percentages of different food types in fisheries catches were obtained by assigning individual target species/taxa to the appropriate food type category based on life history, size, and habitat preferences of the target species or taxa. Food types mainly consumed by marine mammals are presented in hues of blue and green, and food types that are major fisheries target groups are presented in yellows and reds. Note that food types primarily targeted by fisheries represent only a small proportion of the diet of any marine mammal group.

Competition between Marine Mammals and Fisheries: Food for Thought 101 shore, major fishing grounds gener- spend the majority, if not all, of suitability modeling approach, out- ally lie in close proximity to areas their time living and feeding in the lined in the sidebar below, to map with high human populations, off oceans. Except for a few species the likely occurrence of marine the coasts of industrial fishing that haul out on land during repro- mammal species based on the rela- nations. It is noteworthy that com- ductive seasons or have very small tive suitability of the environment, paratively little catch is taken off coastal ranges, distribution of given what is known about their the coasts of developing countries, marine mammals is not restricted habitat preferences. Based on our such as in East Africa or even the by the distance to the nearest land- predictions, most of the food that Indian subcontinent, where fish, mass or the climatic conditions marine mammals consume is taken caught mostly by small-scale fish- that largely influence the locations far offshore, in areas where the ers, still represents a major form of of fishing grounds and major majority of fishing boats rarely ven- sustenance and is often the only human settlements. Conversely, ture. Often cosmopolitan in their source of animal protein (Delgado many species occur predominantly distributions, the baleen and large et al. 2003). Moreover, the majority in geographic areas still largely toothed whale species, for example, of catches that are taken along the inaccessible and/or rarely frequent- likely are feeding mostly in the open coasts of developing countries (e.g., ed by humans, such as the ice- oceans. Due to the sheer size of the along the coast of northwest Africa) breeding seals of the Northern and feeding ranges of these species, are not harvested by local fishers, Southern hemispheres or many of consumption densities (annual food but rather by the large trawlers of the dolphin or whale species pre- intake per km2) are comparatively distant water fleets of industrial dominantly occurring in tropical low and fairly homogeneous across nations (Bonfil et al. 1998). offshore waters. Because of the large areas. Food intake of the vastness of the oceans and the elu- smaller dolphin species is even Where Are Marine siveness of many species, it is diffi- lower and appears to be concentrat- Mammals? cult to determine accurately where ed in temperate waters. Unlike humans, marine mammals they occur and feed. food consumption, in contrast, are true creatures of the sea and Here we have used a novel habitat tends to be associated more closely

Modeling and Mapping Large-Scale Marine Mammal Distributions: We May Know More than We Think We Know... Delineation of marine mammal dis- be the maximum boundaries of a fer. Or put differently, the model rig- tributions is greatly hampered by the given species’ occurrence. We have orously defines the geographic vastness of the marine environment developed a rule-based approach to regions that experts describe when and the low densities of many map the distributions of 115 marine they talk about a “coastal, tropical species. Since marine mammals mammal species in a more objective species” (e.g., the Atlantic hump- spend the majority of their lives way by exploiting various types of backed dolphin) or a species that under water and roam widely quantitative and qualitative ecologi- “prefers offshore, polar waters” throughout oceans, it is difficult to cal information, including (but not (e.g., the hooded seal). Although the determine whether a species fails to limited to) expert knowledge and actual occurrence of a species will occur in a particular area or whether general observations (Kaschner depend on a number of additional we have not spent enough time 2004). Within a global grid (described factors, extensive testing of the looking for it or simply missed it in the sidebar on page 100) we used model shows that it can already when we did look there. All of these our model to relate quantitatively describe, even in its present simple factors contribute to the difficulties what is known about a species’ gen- form, known patterns of species we encounter when trying to map eral habitat preferences to the envi- occurrence quite well (Kaschner et distributions of any whale, dolphin, ronmental conditions in an area, thus al. in review; Kaschner et al. in or pinniped species. Consequently, effectively showing where the envi- prep.). The predicted distributions most published maps of distribution ronment may be suitable for a partic- for the 115 marine mammal species are tentative, often consisting only ular whale, dolphin, or pinniped considered here can be viewed of outlines, sketched by experts species, given what we know about online at www.seaaroundus.org. who represent what they believe to the types of habitat they tend to pre-

102 The State of the Animals III: 2005 Figure 3 Where Are Fisheries?

Map of predicted spatially explicit global fisheries catch rates during an average year in the 1990s, generated through spatial-disaggregation of reported annual catches in a global grid of 0.5° lati- tude by 0.5° longitude cell dimensions using a rule-based approach (sidebar on page 100) (based on data from Watson et al. 2004, with catches averaged over the last decade). Highest concentra- tions of fisheries catches are taken from Northern Hemisphere shelf areas and from the highly pro- ductive upwelling systems around western South America and Africa. Note open-ended scale of legend and that top fisheries’ catch rates (dark red) in some areas can amount to more than a thou- sand tons per km2 per year—more than one hundred times as much as the maximum marine mammal food consumption rates predicted anywhere in the world (Kaschner 2004). with coasts and shelf areas, with food intake rates that are related must consider not only how much feeding taking place mostly in the to a specific feature of our model- both players take where, but also polar waters of both hemispheres ing approach, which relies on glob- what they take. To assess this, we and the restriction to smaller areas al abundance estimates to gener- produced global maps showing the in combination with high abun- ate local densities and which overlap in resource exploitation dances of most species results in currently ignores, for example, the between the major marine mam- much higher, locally concentrated effects of population structure and mal groups and fisheries (Figure feeding densities. differences in the recovery status 4), using an approach that consid- Overall, the concentration of or relative abundance between ers not only the extent of spatial food intake in the higher latitude, individual subpopulations.5 and dietary overlap, but also the polar waters would be even more relative importance of a given area pronounced if seasonal migrations Where They Meet to either group (sidebar on page and feeding patterns of different Using the predicted geographic 105). Areas of overlap between species were incorporated into our distributions of marine mammal fisheries and marine mammal model, particularly those of baleen food consumption and fisheries groups are mostly concentrated in whales. We also need to stress that catches, we now investigate the the Northern Hemisphere and some areas of apparent high con- extent to which they overlap. appear to occur primarily between sumption, such as the South and Again, however, to address the pinnipeds and fisheries. In con- East China seas for the baleen issue of potential competition, we trast, fisheries’ overlap with baleen whales, represent overestimates of whales is relatively low, and pre- Competition between Marine Mammals and Fisheries: Food for Thought 103 Figure 4 Where Do They Meet?

4A 4B

4C 4D

Maps of estimated spatially explicit resource overlap between baleen whales and fisheries (4A), pinnipeds and fisheries (4B), large toothed whales and fisheries(4C), and dolphins and fisheries (4D) (from Kaschner 2004). Maps were produced by computing a modified niche overlap index for each cell in the global grid (sidebar on page 105). The overlap index is based on a comparison of similarity in the composition of diets of marine mammal species and catches of global fisheries in a particular cell, as represented by the proportions of different food types taken by each player in this cell, then weight- ed by the proportion of total global catch and food consumption taken in the cell. Overall predicted overlap between any marine mammal group and fisheries is quite low from a global perspective, with only a few potential, isolated hot spots concentrated in shelf areas. Specifically, overlap between pin- nipeds and dolphins is predicted to be higher in the Northern Hemisphere, while overlap between baleen whales and large toothed whales appears to be higher in the Southern Hemisphere. Compari- son with mapped fisheries catch rates suggests that areas of potential high conflict are largely driven by high concentrations of fisheries catches taken from relatively small areas. Predictions of high overlap in some areas, such as the northwestern Pacific for the baleen whales, are misleading because these are based on overestimates of food con- sumption in these areas. Overestimates are due to a specific feature of our modeling approach that does not account for the effects of population structure and varying degrees of depletion of different populations of the same species (Kaschner 2004). dicted hot spots in the western species and mesopelagic fish, not somewhat myopic. However, to put North Pacific are largely due to the currently exploited by fisheries. the size of the potential overlap biases associated with determining problem into perspective, we cal- food consumption discussed in the How Big of a Problem culated the proportion of food con- previous section. Partially due to Is That? sumption that stems from areas of dolphins’ comparatively low total Overlap between marine mammal predicted high overlap (Figure 5). food intake, the overlap between groups and fisheries is probably In the 1990s, on average, only fisheries and this group is quite low not a global issue but is restricted about 1 percent of all food taken and again mostly concentrated in to a few relatively small geographic by any marine mammal group was the Northern Hemisphere. Not sur- regions and a few species. consumed in areas with significant prising, the lowest overlap occurs The skewed perception of this spatial and/or dietary overlap with between fisheries and deep-diving, problem by nations in close vicini- fisheries catches, indicating that large toothed whales, whose diets ty to these hot spots of interaction both players should be able to co- primarily consist of large squid becomes understandable, if still exist quite peacefully in most of

104 The State of the Animals III: 2005 the world’s oceans.6 potential effects of the increasing The 10–20 percent of global fish- population of South African fur Biological eries catches taken in areas of seals on the hake stocks in this Complications potential high overlap represents a area (Wickens et al. 1992; Punt It is generally agreed that far more relatively significant amount, of and Butterworth 2001). These complex models are needed, incor- course. Recall, however, that over- and other hot spots will require porating many additional parame- lap does not automatically equal much more detailed investigation ters and requiring more, often still competition, and our results likely to establish the true extent of the unavailable data (DeMaster et al. over- rather than underestimate problem at hand. 2001; Harwood 2001; Internation- overlap for the reasons outlined in al Whaling Commission 2003) to the previous sections. Moreover, as shown by comparing the maps of food consumption and fisheries catches, areas of high overlap Spatial Overlap of Marine appear to be associated largely Mammal Food Consumption with areas of extreme concentra- tions of fisheries extractions, and Fisheries Catches: rather than locally concentrated food intake by marine mammals. Where They Meet It is therefore more likely for fish- eries to affect marine mammal In assessing potential competition index of resource exploitation over- species adversely in these areas of between top predators in marine lap for each individual cell in our intense fishing than vice versa, as ecosystems, such as humans and global raster with 0.5° latitude by has already been suggested else- many marine mammals, the ques- 0.5° longitude cell dimensions. The where (DeMaster et al. 2001). For tion of who is eating/catching what index is a modified version of one species with large distributional where is very important, as this developed initially to investigate the ranges, such as the , greatly determines the degree of overlap in ecological niches the reaction to any potential local overlap between the two. This between two species (MacArthur depletion of prey species by fish- question could not be addressed— and Levins 1967), based on the eries may only be to shift to alter- at least not on a large scale—before comparison of similarity in resource nate feeding grounds. For those the development of mapping tech- exploitation of both species. Here, species with very restricted niques for marine mammal distribu- we compared the similarity in the ranges, such as the vaquita in the tions and fisheries catches, such as composition of diets of marine Gulf of California or South Africa’s those described in the sidebars on mammal groups and catches of Heaviside’s dolphins, such local pages 100 and 102. Thanks to our global fisheries in a particular cell depletions of food resources by novel approach for mapping large- represented by the proportions of intensive fisheries may pose seri- scale distributions of marine mam- different food types taken by each ous threats to the survival of the mal species, we were able to pro- player in this cell, then weighted the species. duce global maps showing where qualitative index of diet similarity by Overall, our analysis indicates specific species are likely to feed by the proportion of total global catch that potential competition may linking our predictions about the and food consumption taken in this be addressed better at a local likely occurrence of individual cell to get a sense of the relative level. We also note that most of species (sidebar on page 102) to the contribution of each cell to either the potential hot spots highlight- outputs from the basic food con- total marine mammal food con- ed by our approach are in areas sumption model (sidebar on page sumption or fisheries catches that have been the focal point of 98). Food consumption maps for (MacArthur and Levins 1967; Trites, much debate about marine mam- groups of species were then gener- Christensen, and Pauly 1997; mal-fisheries interactions, such ated by totaling food consumption Kaschner 2004)18. The resulting as in the Bering Sea, with the rates across all species within each maps (Figure 4) represent the area potential negative effects of U.S. group of marine mammals. To where conflicts between specific groundfish fisheries on the en- assess the degree to which there groups of marine mammals and dangered western population of may be conflict between fisheries fisheries may occur: both players Steller sea lions (Fritz, Ferrero, and marine mammals, we quantita- potentially are taking comparatively and Berg 1995; Loughlin and tively compared “who is likely tak- large amounts of similar food types York 2000) or the Benguela sys- ing what where” by computing an in the same geographic region. tem off southwest Africa, with the

Competition between Marine Mammals and Fisheries: Food for Thought 105 adequately address interactions with attempts to increase fisheries should speak of “food webs.”7 Fine- between marine mammals and catches by culling marine mam- ly patterned food webs do not func- fisheries—and the potential far- mals in those areas where compe- tion as efficiently as a simple food reaching effects of the removal of tition is most likely. chain would: much of the top predators from marine ecosys- synthesized by phytoplankton fails tems (Ray 1981; Parsons 1992; to reach higher trophic levels and Pauly et al. 1998b; DeMaster et al. Beneficial is diverted instead into unproduc- 2001) in those areas where com- Predation: tive pathways, notably the so-called petition may occur. The assump- microbial loop. On the other hand, tions, structures, and data needed We May Be in this diversity of pathways protects for such models have been re- predators against the disappear- viewed extensively elsewhere for Surprises ance of any of their favorite prey (DeMaster et al. 2001; Harwood Although the term is species (Neutel, Heesterbeek, and 200l; International Whaling Com- often used when describing the de Ruiter 2002). It is not surpris- mission 2003). However, here we feeding interactions underlying ing therefore that higher-level highlight the problems associated marine structure, we predators, such as or dol-

Figure 5 And How Big a Problem Is That?

Proportion of mean annual global catch/food consumption taken by baleen whales (A), pinnipeds (B), large toothed whales (C), and dolphins (D) in the 1990s in areas of predicted high or low resource overlap, respectively (from Kaschner, 2004). Note that in all cases more than 99 percent of all marine mammal food consumption stems from areas of very low overlap. Similarly, more than 85 percent of all fisheries catches are taken in areas of very low overlap (Kaschner 2004).

106 The State of the Animals III: 2005 Figure 6 We May Be in for Surprises

Schematic representation of beneficial predation: whale species A feeds on both prey species B and prey species C, the latter a commercially harvested species. In addition, prey species B also feeds on prey species C. This means that a decrease in whale species A actually may result in a net increase of predation on prey species C through B, resulting in an overall decrease of commercially harvested species C. Thus, a reduction in predators will not necessarily result in an increase in a particular prey species. phins, consume a wide range of the biomass of C to increase or be fishery enhancer will find him- prey and concentrate on distinct even for its production to become self ultimately culling 20-centime- species only in certain places or at available to a fishery. Rather, it is ter fish so that he can catch more certain times of the year. This fea- more likely that B (whose numbers 5-centimeter fish, thus competing ture of marine food webs is also the were also depressed by A) will with birds, squids, and jellyfish. reason why removing a higher-level increase and consume more of C Beneficial predation is not an ad predator does not necessarily lead (Walters and Kitchell 2001). If B hoc concept invented to discourage to an increase of what, at certain happens to be a species that fish- would-be cullers of marine mam- times and places, appears to be its eries do not exploit, this will result mals. Rather, counterintuitive re- “preferred” prey (Parsons 1992; in the production of C being wast- sults of removing high-level preda- Cooke 2002). Basically, predators ed from the standpoint of fishery tors from ecosystems have been well not only consume their favorite D. Indeed, to acquire the produc- demonstrated in various cases, prey but also the competitors and, tion of C, we would have to cull B based on a number of modeling in many cases, the predators of as well and so on ad infinitum. This approaches (Parsons 1992; Caddy their prey (Parsons 1992; Punt and conundrum has caused ecologists and Rodhouse 1998; Yodzis 1998, Butterworth 2001; Cooke 2002). to coin the term “beneficial preda- 2001; Crooks and Soulé 1999; This is illustrated schematically in tion”—that is, a form of predation Pauly, Christensen, and Walters Figure 6 in the form of a feeding wherein the predator (here, A) 2000; Punt and Butterworth 2001, triangle, representing a ubiquitous enhances the production of its prey Bjørge et al. 2002; Okey et al. 2004; feature of marine food webs. Here, (here, C) by suppressing potential Morisette, Hammill, and Savenkoff, a high-level predator, represented competitors or predators (here, B). submitted for publication).8 In fact, by a toothed whale (A), feeds on This effect is very common in it has been proposed as one reason two species (B and C), with C marine food webs. Indeed, essen- for a stagnation in global ground- being the preferred prey, which is tially all marine food webs can be fish landings since the 1970s, as it also exploited by commercial fish- conceived as composed of inter- is possible that the reduction of eries (D). B, however, also preys on linked sets of feeding triangles toothed whales and other high-level C (and other organisms—E, F, and shown schematically in Figure 6. predators that feed on desirable fish so on—of no concern here). In Removing what appears to be a top species but also on various squids, such cases, removing species A will predator in such cases only creates which in turn feed on juvenile not necessarily make it possible for new top predators, and the would- groundfish, has contributed indi- Competition between Marine Mammals and Fisheries: Food for Thought 107 rectly—through an increase of Contrary to popular opinion, the cephalopod consumption of juve- Other Legitimate , sardines, , and nile fish—to the inhibition of finfish Questions other species ground up to produce population recovery (Caddy and the fish meal that is fed to carnivo- Rodhouse 1998; Piatkowski, Pierce, Who Would Get rous fish are, when suitably handled, and Morais da Cunha 2001). the Fish? perfectly edible by humans and are indeed appreciated in many parts of Although this may seem beside the the world. These fish are increasing- How Much point, we must highlight the ques- ly hard to find in the markets of Culling—If Any— tionable use of world hunger as a developing countries, in areas such justification for culling marine as West Africa, where, being relative- Is Enough? mammals and subsequently target- ly cheap, they represented the major ing their prey.10 One important assumption in the source of animal protein for poor Though an estimated 950 million context of competition is that people (Naylor 2000).12 Given these people worldwide currently rely on marine mammal food consump- trends, and increasing fish exports fish and shellfish for more than tion increases directly with marine from developing to developed coun- one-third of their animal protein mammal abundance. Though this tries, it would be completely unreal- (Plagánzi and Butterworth 2002), is obviously true in general,9 other istic to assume, and disingenuous to the per capita supply of wild-caught factors, such as the vulnerability of claim, that the meat of culled fish for human consumption has prey species to predation (Mackin- marine mammals or that of their been declining since the mid- son et al. 2003), the ability of the former prey would become a substi- 1980s, particularly in developing predator to switch between prey tute for the fish that is now export- countries.11 This is due in part to species, and movements of animals ed from countries where people “do , which has led to the between different areas, greatly not have adequate food” (Institute decline of global catches since the influences how much a given of Cetacean Research 2001b). late 1980s (Watson and Pauly 200l; species eats in a specific area. The Indeed, it is precisely the low pur- Pauly et al. 2002, 2003), but also to flip side of this, then, is that it may chasing power of the people in these human population growth. Indeed, be impossible to determine exactly countries that prevents them from no natural resource, including wild- how many animals would need to competing successfully with fish caught fish, could ever meet our be culled to achieve the desired meal producers and fish feedlot ever-growing demand. We will not increase in fisheries catches. A operators. elaborate on the fact that of the study investigating this showed 120–150 million or so tons of fish that, even for a very simple food and invertebrates killed annually by web, many likely scenarios existed Are We Simply fisheries, only about half is actually in which consumption of a given eaten by people: about thirty mil- Looking for prey species by a marine mammal lion tons of are discarded species would only decrease Scapegoats? or killed by lost gear (ghost fish- noticeably if the predator popula- Unlike earlier fisheries declines, ing), while a huge amount is lost to tion was reduced by more than 50 which passed mostly unnoticed by spoilage (Ward and Jeffries 2000) percent (Cooke 2002). Given the the general public, the massive and during processing (e.g., gut- wide-ranging movements of most fisheries collapses of the last ting, filleting) (Bykov 1983) or left species and the fact that fish and decades had a broad public impact, uneaten, in richer countries, at the marine mammals tend not to so they have generated widespread edge of consumers’ plates. Another respect human management calls for mitigation (Food and Agri- thirty million tons, however, are fed boundaries, it is highly question- cultural Organization of the United to various livestock (Pauly et al. able that we would ever be able to Nations 1995). In particular, peo- 2002) and carnivorous fish— manage marine mammal popula- ple have noted that fisheries man- notably salmon, sea bass, groupers, tions in a manner guaranteed to agement has tended so far to focus and tuna—in indus- produce a measurable, long-term on single stocks, thus neglecting tries, which are one of the driving increase in fisheries catches. feeding and other interactions factors behind the increased fish among different species/stocks and exports from developing to devel- their dependence on the health of oped countries, especially to the their ecosystems. There have been, United States, the European as a result, increasing demands for Union, and (Naylor 2000; ecosystem-based fisheries manage- Alder and Watson, in prep.). ment, or even “ecosystem manage-

108 The State of the Animals III: 2005 ment.”13 The scientific community find a convenient scapegoat for the culled, and, indeed, saving seabirds has accepted this challenge, and, mismanagement of fisheries (Holt from death (e.g., by entanglement for the last few years, a lively scien- 2004) and the reduction of catch- in fishing gear) is one of the few tific debate has been conducted in es caused by excess fishing effort conservation-related activities that many national and international throughout the world. This puts is never disparaged in public, even arenas on this topic. The principal the following quotation in context: though it greatly affects the man- questions asked deal with how to The FAO considers that we can- ner in which some fisheries opera- implement such a broad form of not increase the harvest from tions are conducted. management and how to identify the ocean if we continue present Clearly, if those proposing a suitable indicators and formulate practices. To increase the catch global attack on marine mammals fisheries target and reference from the ocean, holistic man- were consistent, they also should points within an ecosystem con- agement and sustainable utiliza- propose that we go after the sea- text.14 This includes the challenge tion of marine resources includ- birds. More important, we should of achieving set conservation objec- ing marine mammals, such as eliminate all large fish as well, tives for predators of species target- whales, is essential. (Institute of since they eat immense numbers ed by fisheries (Constable 2001). Cetacean Research 2001a, n.p.) of other fish, shrimps, and squids, Those who advocate a broad- This, indeed, is a beautiful exam- generally far more than taken by based attack on marine mammals, ple of a non sequitur: yes, we can- marine mammals and seabirds on the other hand, behave as if they not increase landings “if we contin- (Livingston 1993; Trites, Chris- already have the answers. Because ue present practices.” But the tensen, and Pauly 1997). Indeed, most fish stocks of the world have present practices are character- the greatest predators of fish are been overexploited (including those ized by waste (e.g., bycatch [North- other fish (Trites, Christensen, and on which marine mammals rely), ridge 1984, 1991; Alverson et al. Pauly 1997; Furness 2002). But the mantra coming from this latter 1994], discarding [Alverson et al. again we are eliminating large group is that all we have to do is 1994] ghost fishing [Breen predatory fish anyway, as we fish remove marine mammals until the 1990]), and pathological manage- down marine food webs, reducing original balance is re-established. ment structures (e.g., excess fish- high-level predator biomasses as Here is a quote to that effect: “When ing capacity [Mace 1997] and sub- we go along (Pauly et al. 1998b; a single species is protected, ignor- sidies [Munro and Sumaila 2002]), Christensen et al. 2003; Myers and ing its role in the ecosystem, the bal- and these are the practices that, all Worm 2003). Nevertheless, overall ance in the ecosystem is disrupted” experts agree, must be overcome, catches are decreasing,16 notably (Institute of Cetacean Research rather than killing more whales, because, in the process, we are 2001b, n.p.). Albert Einstein is sup- even if we think holistically. eliminating beneficial predation. posed to have noted that “all com- plex problems have one simple solu- tion; however, it happens to be And How about Conclusions completely wrong.” Here, not only the Birds? We have shown that, even though have the fish been overexploited, but marine mammals consume a large No one has proposed (so far!) so have the marine mammals. Given quantity of marine resources as a killing all seabirds to increase fish reduced fishing pressure, fish can be whole, there is likely relatively little available for human consumption. expected to recover faster15 than actual competition between “them” There are millions of seabirds in marine mammals (Best 1993; Trites and “us” from a global perspective, the world, consuming massive et al. 1999), given their respective mainly because they, to a large amounts of fish, squid, and other reproductive abilities. Indeed, all extent, consume food items that we valuable invertebrates. Although recent evidence confirms that do not catch in places where our birds tend to weigh little individu- baleen whales are far less abundant fisheries do not operate. This is not ally, their high metabolic rate leads than they were historically (Brown- to say that there may not be poten- to very high food consumption ell, Best, and Prescott 1983; Perry, tial for conflict in the small geo- rates (Ellis and Gabrielsen 2002). DeMaster, and Silber 1999; Clap- graphic regions in which marine Thus, in the aggregate, seabirds ham, Young, and Brownell 1999; mammal food consumption overlaps have been estimated to consume Clapham and Baker 2002; Holt with fisheries. These areas warrant 50 to 80 million tons of fish and 2002). Re-establishing the disrupted further investigation. But even in invertebrates per year (de L. balance of ecosystems is therefore these cases, it seems likely that the Brooke 2004), at least half of what hardly a simple matter of reducing most common type of competitive humans kill annually. Yet no one whale numbers. interaction will be one where fish- has proposed that seabirds be What we have is an attempt to eries have an adverse impact on

Competition between Marine Mammals and Fisheries: Food for Thought 109 marine mammal species, especially Notes nature_china/30jan02.asp. . l2 those with small, restricted distribu- 1Granted, in combination with some fairly Another example: Chilean sardine, once sophisticated spatial modeling techniques a staple food, is now scarce on Chilean mar- tional ranges (DeMaster et al. 2001; (Kaschner 2004; Kaschner et al. in review; kets, because most of the catch is ground up Holmes 2004; Kaschner 2004). Our Kaschner in prep.; Watson et al. 2004). into fish meal to feed an export-oriented analysis clearly shows that these are 2 We estimated only about 1 million baleen salmon industry so huge that it has consumed whales worldwide, versus about 35 million pin- the bulk of the stocks of small pelagic fish isolated, regional issues to be nipeds and 16 million dolphins (Kaschner once available in the rich waters of that coun- addressed at the appropriate scale, 2004). try (Fulton 2003). Our last example is the and that there is no evidence that 3That is, the effects of a species switching rapid development in several Mediterranean between feeding on 50 percent and 50 countries of massive tuna feedlot operations food competition between marine percent in different seasons or in dif- in which immense quantities of the sardine mammals and fisheries is a global ferent areas of its range can be ignored, and other small fish much appreciated around problem, even when the uncertain- because it would still have a proportional diet the Mediterranean are used to fatten tuna, composition consisting of 50 percent of the which are then flown to Japan, where, like ties associated with the available “small pelagics” food type. salmon, they enter a developed-country luxu- information are considered. Thus, 4For example, though the “diet” of both a ry market (Aguis 2002). 13 there is little basis to blame marine fishery and a marine mammal species may For example, at the World Summit on consist of 50 percent “small pelagics,” the Sustainable Development held in Johannes- mammals for the crisis world fish- fishery may be targeting different small pelag- burg, South Africa, in 2002, organized by the eries are facing today. There is even ic species from those consumed by the marine United Nations Commission on Sustainable less support for the suggestion that mammal. Development (www.johannesburgsummit.org). 5As a result, in the North Pacific, for exam- 14For example, at the Quantitative Ecosys- we could solve any of these urgent ple, the healthy and growing Eastern subpop- tem Indicators for global problems, caused by a long ulation of eighteen to twenty thousand gray symposium, Paris, 2004, organized by the IOC history of mismanagement of fish- whales that feeds and breeds along the Pacific International Ocean Commission/Committee coast of North America (Angliss and Lodge at UNESCO headquarters (www.ecosyste- eries and other resources, by reduc- 2002; Perryman et al. 2002; Wade 2002) effec- mindicators.org). ing marine mammal populations. tively “subsidizes” the highly depleted West- 15As they did, for example, during World We may spend some time, however, ern subpopulation. This latter subpopulation War II in the North Sea, which was mined and historically occurred all along the coasts of too dangerous to fish (Beverton and Holt thinking about the fact that marine Russia and Japan and probably as far down as 1957). mammals—and other top preda- the East China Sea, but is now on the brink of 16Given that biological production is tors—have been managing marine extinction, reduced to barely a hundred ani- greater at lower than at higher trophic levels mals concentrated in the Sea of Okhotsk (TL), fisheries catches, initially at least, will resources successfully, consuming (Weller et al. 2002a,b). tend to increase when TL decline (i.e., when larger amounts than those taken by 6When viewed from the perspective of fish- the fisheries target species is lower in the food global fishing operations today, for eries, the overlap is slightly more pronounced, web) (Pauly et al. 1998b). This led to the sug- with less than 15 percent of all fisheries catch- gestion of an FiB index, which, given an esti- millennia. Unlike us, they appear to es likely being caught in the areas that show mate of the biomass (or energy) transfer effi- have done so sustainably, without up as hot spots on our maps (Kaschner 2004). ciency (TE; often set at 0.1[Pauly and causing their prey species to col- 7Thus, the basic food produced at the bot- Christensen 1995]) between TL, maintains a tom of marine food webs, mainly by minute value of zero when a decrease in TL is lapse. Perhaps we could learn some- phytoplankton, is consumed by herbivores of matched by an appropriate catch increase thing from them. It’s food for various sizes, some with a narrow range of pre- (and conversely when TL increase) and devi- thought. ferred algal species, while others, facultative ates from zero otherwise. The FiB index is herbivores, also consume fellow zooplankters. defined, for any year y, by From there, the pathways that biomass can FiBy = log{[Yy · (1/TE)TLy] / [Yo · follow along the food web branch even further, (1/TE)TLo]} Acknowledgments leading to small fish or large zooplankton, where Yy is the catch at year y; TLy is the both consumed by larger fish or invertebrates, mean of the catch at year y; Yo is We acknowledge funding provided themselves consumed by a wide array of high- the catch and TLo is the mean trophic level of for this report by The Humane er-order predators. the catch at the start of the series being ana- Society of the United States 8Incidentally, the trophic dynamic software lyzed (Pauly et al. 1998b). Note that the FiB package & Ecosim, widely applied to index is designed so that it does not vary dur- (HSUS). The underlying research construct, balance, and analyze marine food ing those periods when changes in TL are was conducted as part of the “Sea webs and often used to investigate the effects matched by catch changes in the opposite Around Us” Project, with funding of beneficial predation, was also used recently direction, that is, periods within a time series by ardent advocates of massive culls based at where the FiB index does not appear to provided by the Pew Charitable Japan’s Institute of Cetacean Research. They change. Conversely, an increase of the FiB Trusts of Philadelphia, Pennsylva- conveniently failed to notice this feature of index indicates that the underlying fishery is nia, and via Daniel Pauly by the the software, however. expanding beyond its traditional fishing area 9That is, many whales will eat more than (or ecosystem), while a decrease indicates a National Science and Engineering no whales at all. geographic contraction, or a collapse of the Research Council of Canada. Addi- 10An example of a quotation: “Whaling can underlying food web, leading to “backward- tional support for Kristin Kaschner contribute to the world food shortage and bending” plots of TL vs. catch (Pauly et al. in several ways. [...] 1998b). All applications done so far of the FiB was provided by a “Li Tze Fong” whaling is a means of obtaining high quality index indicate that once an area is extensively graduate fellowship and a partial food from the sea without diminishing biodi- fished, “fishing down” (i.e., removing preda- university graduate fellowship from versity and,[...] may allow more fish to be tors) does not increase catches as much as directed to human use” (Institute of would be predicted from the higher produc- the University of British Columbia. Cetacean Research 2001a). tion at lower trophic levels, so, based on the 11Available at: www.fao.org/fi/statist/ FiB index as well, removing top predators from marine food webs appears not to be an

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