true

ISRA FACTSHEETS

NORTH AMERICAN PACIFIC

ISRA FACTSHEETS

NORTH AMERICAN PACIFIC

Kammu Seamount ISRA

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Kammu Seamount ISRA

Kammu Seamount

Summary

Kammu Seamount is located in Areas Beyond National Jurisdiction (ABNJ) in the North Pacific. This ancient underwater volcano sits at the southern end of the Emperor Seamount Chain where it rises about 4,600–4,700 m from the abyssal plain. The depth at the top of the seamount is at ~340–375 m below the surface. Kammu Seamount is comprised of two flat crests which are characterised by deepwater coral reefs. The area is influenced by the southern boundary of the Subarctic Frontal Zone with an eastward water transport direction in the Kuroshio Extension Current. This area overlaps with two Ecologically or Biologically Significant Marine Areas. Within this area there are: undefined aggregations (e.g., Owston’s Chimaera Chimaera owstoni).

Kammu Seamount

Kammu Seamount

DESCRIPTION OF HABITAT

Kammu Seamount (also known as Kammu Guyot) is located in Areas Beyond National Jurisdiction (ABNJ) in the North Pacific. This ancient underwater volcano is a large seamount with a flat top on the Emperor Seamount Chain. It is situated at the southern end of the seamount chain and rises about 4,600–4,700 m from the abyssal plain (Calgue et al. 1980). The depth at the top of the seamount is at ~340–375 m below the surface (Calgue et al. 1980). Kammu Seamount is comprised of two flat crests, elongated northwest-southeast (Calgue et al. 1980). Seamounts/guyots of the southern Emperor Seamount Chain are characterised by deepwater coral reefs (Dautova 2025).

The area is influenced by the southern boundary of the Subarctic Frontal Zone with an eastward water transport direction in the Kuroshio Extension Current (Zuenko & Kurnosova 2025). The Subarctic Frontal Zone separates cold, fresher, Subarctic water to the north from warmer, more saline, subtropical water to the south (Yuan & Talley 1996). Seamounts on the Emperor Seamount Chain have heightened biological productivity relative to surrounding oceanic zones (Zuenko & Kurnosova 2025).

This area overlaps with the Emperor Seamount Chain and Northern Hawaiian Ridge Ecologically or Biologically Significant Marine Area (EBSA) and the North Pacific Transition Zone EBSA (CBD 2026a, 2026b).

This Important Shark and Ray Area is benthic, pelagic, and subsurface and is delineated from 320–645 m based on the depth range of Qualifying Species in the area.

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Kammu Seamount is an important area for undefined aggregations of one shark and one chimaera species.

Between 1979–2023, fishing surveys (n = 1,789) were conducted across the Emperor Seamount Chain with 14.1% occurring inside this area (n = 253; Volvenko 2014, 2015; IV Volvenko & AM Orlov unpubl. data 2025). Surveys were conducted every year except for the periods 1989–1992, 1994–2005, and 2007–2008 (surveys were conducted in different months across years). Fishing gear consisted of midwater trawls and benthic trawls at depths between 0–1,200 m and 160–1,340 m, respectively. Trawl parameters were variable with haul time ranging <1–12 hours (mean = 1 hour); haul speed ranging 1.5–6.5 knots (mean = 3 knots); and horizontal trawl opening ranging 11–100 m (mean = 28 m). In addition to these trawl surveys, between 2014–2018, catch data from scientific observers on longliners were recorded (215–1,840 m depth; each line was 900 m long with 640 hooks, with 1–12 lines deployed and retrieved per day; IV Volvenko & AM Orlov unpubl. data 2025). Catch-per-unit-effort (CPUE) was estimated as the number of individuals per area fished during the haul (multiplying the haul time by the haul speed and the horizontal opening of the trawl) and standardised as individuals/km2. For longline sets, CPUE was estimated as the number of individuals caught per 1,000 hooks per 1 h (ind./1,000 hh).

Deepwater sharks, skates, and chimaeras are known to aggregate with temporal changes related to sex and life-stage segregations (e.g., Yano & Tanaka 1988; Swain & Benoît 2006; Coelho & Erzini 2010; Frisk 2010; Hoff 2010; Finucci et al. 2018). Species can aggregate in high density areas resulting in large catches in specific areas within the broader seascape (e.g., Bizzarro et al. 2014). Elevated CPUE relative to surrounding areas can be used as an indicator of aggregations of deepwater species (Orlov & Volvenko 2022). Specifically for lanternsharks and chimaeras, high densities of individuals have been shown to be indicative of aggregations (Finucci et al. 2018). Through social association analyses, species of lanternsharks and chimaeras have been shown to have strong associations between individuals, often between the same life-stage (e.g., juveniles, adults) and sex (Finucci et al. 2018).

Across the broader Emperor Seamount Chain, 69,174 Smooth Lanternsharks were recorded in 800 hauls/sets during these surveys, of which 61 hauls/sets (7.6%) were conducted inside this area. Of these records, 67,552 (97.6%) originated from contemporary years (all years between 2010–2019) and 8,946 individuals (13.2%) were recorded inside this area. The highest CPUE (average = 345.1 individuals/km2; max = 4,452.6 individuals/km2) was recorded at Kammu Seamount, compared to all the seamount chain (average CPUE outside the area = 25.4 individuals/km2; max = 2,026.4 individuals/km2). The presence of aggregations was confirmed when >10 Smooth Lanternsharks were recorded in a single haul/set. Aggregations were recorded in 33 instances (54.1% of the surveys conducted inside this area) with an average of 223 individuals recorded per haul/set and a maximum of 3,456 individuals. These aggregations were recorded at depths of 323–645 m. The presence of Smooth Lanternshark aggregations may be related to feeding on schools of epipelagic fish migrating from Asia to this area (Volvenko et al. 2025).

Across the broader Emperor Seamount Chain, 333 Owston’s Chimaeras were recorded in 143 hauls/sets during these surveys of which nine hauls/sets (6.3%) were conducted inside this area. Of these records, 321 (96.4%) originated from contemporary years (all years between 2011–2018) and 35 individuals (11.0%) were recorded inside this area. The second highest CPUE (average = 1.4 individuals/km2; max = 30.1 individuals/km2) was recorded at Kammu Seamount compared to all the seamount chain (average CPUE outside the area = 0.4 individuals/km2; max = 1.2 individuals/km2) after Koko Guyot. The presence of aggregations was confirmed when >5 Owston’s Chimaeras were recorded in a single haul/set. Aggregations were recorded in five of the six surveys (83.3%) conducted inside this area in contemporary years with an average of six individuals recorded per set and a maximum of ten individuals. These aggregations were recorded at depths of 457–645 m.

Additional information is required to understand the nature and function of these aggregations.

Kammu Seamount

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