There is a lack of information available on the biology of many shark species worldwide. The following section highlights some of the information that is currently available.

The IUCN report, Sharks and their Relatives, provides estimates of intrinsic rates of increase (r) (listed as “Annual rate of population increase”) for 31 species of sharks. Values for r range from 0.012 (Lemon Shark) to 0.136 (Brown Smoothhound) (Camhi et al. 1998). Two species commonly caught in the United States, Sandbar and Blacktip Sharks, have higher intrinsic rates of increase. Mean values for these two species are 0.12 and 0.19, respectively (Cortes 2002).

Estimates of age at maturity are available for some of the species covered in this evaluation; these include: 5-5.8 years (Common Thresher Shark); 8-13 years (Great White Shark); 4-5 years (Oceanic Whitetip Shark), 15-16 years (Sandbar Shark); 4-6 years (Blue Shark); 7-11 years (Tiger Shark) (Carrier et al. 2004);

Growth rates (k) are reported for the following species: 0.124-0.184 (Common Thresher Shark); 0.065 (Great White Shark); 0.0996-0.103 (Oceanic Whitetip Shark); 0.039-0.087 (Sandbar Shark); 0.178 (Tiger Shark); 0.1-0.144 (Blue Shark) (Carrier et al. 2004).

Many species of sharks have relatively long life spans. Estimates of maximum age for some species included in this evaluation are: 22 years (Common Thresher Shark), 11-17 years (Oceanic Whitetip Shark), 18-25 years (Sandbar Shark); 15-16 years (Blue Shark); 8-27 years (Tiger Shark) (Carrier et al. 2004).

To account for the large number of species for which intrinsic rates of increase are below 0.05, and whose growth rates are less than 0.15, a low score was awarded here.

Many shark species require pupping or nursery grounds. These areas may be inshore, offshore, or in estuarine areas where vulnerability to fishing pressure and habitat alteration may be higher than in the open sea. For example, sandbar sharks in the Western North Atlantic utilize shallow bays and estuaries of the east-central USA for pupping. Many shark species also tend to aggregate by age, sex, and reproductive stage, making them more vulnerable to fisheries (Camhi et al. 1998). Sandbar Sharks, for example, travel in large schools as they migrate southward in winter along the Western North Atlantic seaboard. And Blacktip Sharks occur in large schools in surface waters (IUCN 2000).

Many sharks are long-lived species, with life history strategies that have evolved with few predators. Sharks have low reproductive potential, with reproductive strategies that are more similar to those of cetaceans, sea turtles, large land mammals and birds than those of other teleost fishes (Camhi et al. 1998). For example, many species of sharks have as a few as 2 pups at a time and reproduce only once every 2 years (e.g. Tiger shark, White shark, Silky shark) (Camhi et al. 1998).

Most sharks are wide-ranging and are found in ocean waters worldwide (Fishbase 5/5/03).

Although it is true that highly migratory species are not generally susceptible to environmental variability, some species might be affected by such phenomena. This could be true for species which spend the first period of their lives in nursery areas. If the availability of food in those areas is limited due to environmental conditions the mortality of young sharks might increase. However, there are no strong indications that such effects could result in high natural population variability (Apostolaki, Pers. Comm., 2004). No points were added or subtracted here due to a lack of substantive information.

Estimates of biomass for shark populations relative to a target level such as Bmsy are not available for many shark populations worldwide. The best estimates of abundance outside U.S. waters are available from the IUCN, which has assessed 62 species of sharks and reported their findings in the IUCN Red List of Threatened Species. Of the 62 species assessed to date, most are classified as "Endangered" (facing a very high risk of extinction in the near future), "Vulnerable" (facing high risk of extinction in the medium-term future), or “Near threatened” (IUCN 2002), indicating that of the species assessed from a global perspective, many are at very low levels, or are depleted.

In June 2004 the Sub-Committee on Bycatch of the International Commission for the Conservation of Atlantic Tunas (ICCAT) conducted stock assessments for Atlantic Blue and Shortfin Mako Sharks. ICCAT reported that biomass of Blue Sharks is above the level that would support MSY in the North and South Atlantic. They also reported that biomass of Shortfin Mako Sharks may have declined by fifty percent or more in the North Atlantic. The South Atlantic population has also declined, but the magnitude of decline may be less severe than in the North Atlantic. ICCAT states, however, that the estimates are highly uncertain (ICCAT 2004).

Baum et al. (2003) estimated abundance of shark populations in the Northwest Atlantic. They found that with the exception of Mako Sharks, all recorded species have declined by more than 50% in the past 8 to 15 years. Trends data are not available for shark populations worldwide. However, it is likely that shark populations worldwide are declining, given the fact that most shark fisheries remain unmanaged and the demand for shark products continues to be high, especially outside of the U.S. where shark finning remains legal.

There is very little information available on age, size, or sex distributions for shark species.

Of the 62 species assessed to date, the IUCN lists 21 species as endangered or vulnerable. Currently 31 species are considered close to qualifying for Vulnerable status (officially ranked “Near threatened”) (IUCN 2002). In addition, in October 2004, CITES approved listing the Great White Shark on CITES Appendix II. Species listed under CITES Appendix II include those that may become threatened with extinction unless trade is subject to strict regulation. This listing will come into effect in January 2005 (UNEP-World Conservation Monitoring Centre, Pers. Comm., 2004).

Worldwide, sharks are taken by a variety of gear types and are caught in both industrial and non-industrial (mainly artisanal) fisheries. Non-industrial fisheries are typically located inshore and in coastal waters. These fisheries often take sharks for subsistence purposes using a range of gears. Recreational shark fishers, for example, often use rod and reel and gillnet gear. Artisanal fishers catch sharks with baited hooks on longlines and gillnets. Industrial shark fisheries target sharks with drift net and demersal gillnet gear. Large numbers of sharks are also caught as bycatch in longline, purse seine, and driftnet fisheries that target tunas (Walker 1998).

In the U.S. Atlantic and Gulf of Mexico most sharks are caught by bottom longlines, drift gillnets, and rod and reel (including commercial, recreational, and charter/headboats). Gillnetting is done both by drifting (one vessel, with gillnet set in a straight line that fishes passively) and strikenetting (set rapidly around a school of sharks, or set behind the wake of a shrimp vessel when it begins haulback) (NMFS 2003). In North Carolina, the majority of landings are taken by longlines. Surface longlines are more commonly used in the summer, when fishers are primarily targeting tunas. In the winter, bottom longlines are mostly used. Gillnet fisheries for sharks have largely been eliminated in North Carolina due to interactions with sea turtles. However, some nearshore gillnet fisheries targeting Atlantic sharpnose sharks in the summer still exist in the southern part of North Carolina. In the U.S. Pacific, sharks are taken primarily in drift gillnet fisheries, as well as in some longline fisheries. While less information is available, it is likely that similar gear is utilized in shark fisheries worldwide.

The habitat requirements of sharks vary according to species and according to stages in life cycles. Some sharks, for example, live in kelp forests, among coral reefs, or in deep waters. Other species may be completely dependent on coastal or estuarine habitats. Today coastal habitats are under increasing pressure from development, fisheries activities and pollution. And coral reefs are becoming increasingly more damaged. Because of their life history strategies, sharks may be unable to adapt to changing environmental conditions (Camhi et al 1998).

Coastal and inshore areas are important nursery habitat for sharks and consequently are critical to shark productivity. The amount of suitable nursery habitat available is recognized as a limiting factor on shark populations. For juvenile sharks, inshore areas provide lower predation rates and high forage abundance (PFMC 2002). Although there is research in progress to identify important shark habitat areas, no measures are in place in the Atlantic to protect shark habitat (Fordham and Camhi, 2003). Given that there is little protection for shark habitat in the U.S. and that the U.S. has more shark management in place compared to many other countries, we assume that shark habitat is not being protected worldwide.

No efforts are being made internationally to minimize damage from existing gear.

There is no international management in place for sharks. The IUCN Shark Specialist Group (SSG) and TRAFFIC reviewed progress on the FAO International Plan of Action for Sharks and found that countries fishing for sharks and Regional Fisheries Management Organizations have made negligible progress in implementing the plan. Of the 113 states that report shark landings to the FAO, 18 nations report landings of more than 10,000 t per year. Yet, only 29 states have made any progress with the IPOA. Of the 18 major shark fishing nations, only one has a draft Shark Assessment Report (SAR) and two have completed National Plans of Action (NPOA). Still, all of the NPOAs that the SSG and TRAFFIC reviewed failed to meet all of the standards suggested by the FAO, most likely because the IPOA-Sharks is voluntary and countries do not consider it a priority to follow the FAO IPOA actions (IUCN SSG; TRAFFIC 2002).

In contrast, shark fisheries in the U.S. have some regulations. In addition to the state managed shark fisheries off the U.S. West Coast, shark fisheries in the U.S. Atlantic and Gulf of Mexico are managed by under the Fishery Management Plan for Highly Migratory Species. Also, pursuant to the endorsement of the FAO’s IPOA, the U.S. released a final National Plan of Action (NPOA) for the Conservation and Management of Sharks (66 FR 10484) in 2001. Under the NPOA, NOAA Fisheries is required to undertake data collection, analysis, and management measures for sharks (NMFS 2003).

All countries catching sharks are encouraged by CITES to implement the IPOA-Sharks by developing Shark Assessment Reports and National Plans of Action (NPOAs or Shark Plans) for improved data collection of catch and trade, monitoring and management, international collaboration in shark fisheries management. However, as discussed in the core points section, little progress has been made in shark fisheries worldwide. Also, a major obstacle to assessing the efficacy of shark management regimes, estimating catch rates by species, and monitoring trends in shark trade, is the lack of adequate trade statistics for shark products. Resolution 9.17 of CITES recommended improving trade statistics, yet the World Customs Organization argues that there is no way to improve identification codes for shark products at the level of international trade. The only exception is monitoring trade of CITES-listed species, or for individual countries to add shark commodity identification codes to national customs data recording systems (IUCN SSG; TRAFFIC 2002).

There is little management in place for sharks, including consideration of habitat/ecosystem factors.

The IUCN assessed 62 species of sharks and found that 21 species are considered endangered (facing a very high risk of extinction in the near future) or vulnerable (facing high risk of extinction in the medium-term future). And 31 species are considered close to qualifying for Vulnerable (officially ranked “Near threatened”). Baum et al. (2002) also suggest that the magnitude of declines in shark populations in the Northwest Atlantic could mean that several shark species are at risk of large-scale extirpation. Yet, few countries have recovery plans in place for sharks.

Large Coastal Sharks in the U.S. Atlantic and Gulf of Mexico, with the exception of Sandbar and Blacktip sharks, are overfished. However, Small Coastal Sharks are not considered overfished (NMFS 2003). Off the U.S. West Coast, thresher and mako sharks are not overfished. Rebuilding programs are in place for ridgeback and non-ridgeback Large Coastal Sharks. Precautionary measures are in place for pelagic and Small Coastal Sharks (NMFS 2003).

Because many shark species are taken as bycatch, it is difficult to determine whether or not those fisheries are overcapitalized.

Although information on bycatch in shark fisheries outside the U.S. is not available, estimates from targeted U.S. fisheries suggest that there may be significant bycatch of protected species in shark fisheries worldwide due to the nature of the gear used. For example, observer data from targeted bottom longline fisheries in the U.S. Atlantic and Gulf of Mexico, show that in 1998 catches were comprised of 91.1% sharks, 8.6% other fish, 0.17% invertebrates, and 0.4% sea turtles. Expected annual capture of sea turtles in shark bottom longline fisheries is 2 Leatherbacks, 12 Loggerheads, 2 Green, 2 Hawksbill, and 2 Kemps’ Ridley turtles (NMFS 2003).

In the gillnet fishery off the U.S. West coast, incidental takes of marine mammals (including sperm whales, humpback whales, fin whales, short finned pilot whales, and northern common right whale dolphins) and sea turtles (loggerheads and leatherbacks) were once problematic. Closed seasons and closed areas to protect sea turtles, mandatory use of acoustic pingers to deter marine mammals, and regulations requiring that nets be set 6 fathoms below the surface to avoid marine mammal entanglements were implemented and bycatch has since been reduced (Price, 2003, personal communication). However, in shark fisheries without strong mandates to protect marine mammals and sea turtles, it is reasonable to assume that bycatch may be problematic.

No management measures, inclufing bycatch reduction, are in place in shark fisheries worldwide.

Bycatch of sharks in pelagic longline fisheries targeting swordfish and tunas is very high. Shark bycatch is the most important source of bycatch in these fisheries and populations of almost all sharks caught by pelagic longlines in the Northwest Atlantic appear to be declining (e.g. hammerheads, blue sharks, and porbeagle sharks). In the Northwest Atlantic, 50% of all catch (in weight and numbers) is blue sharks. Non-reported longline catch from the Pacific, Indian and Atlantic Oceans has been increasing since the 1990s, thus bycatch may be even higher in some fisheries (Crowder and Myers 2001). No measures are in place to reduce shark bycatch.

The continued removal of shark species in pelagic longline fisheries drives the decline of shark populations.